Marloes J. A. G. Henckens
Aug 12, 2009; 29:10111-10119
BehavioralSystemsCognitive

Robbert Havekes
Dec 12, 2012; 32:18137-18149
BehavioralSystemsCognitive

Randy L. Buckner
Aug 24, 2005; 25:7709-7717
Neurobiology of Disease

Sleep is known to drive the consolidation of motor memories. During nonrapid eye movement (NREM) sleep, the close temporal proximity between slow oscillations (SOs) and spindles ("nesting" of SO-spindles) is known to be essential for consolidation, likely because it is closely associated with the reactivation of awake task activity. Interestingly, recent work has found that spindles can occur in temporal clusters or "trains." However, it remains unclear how spindle trains are related to the nesting phenomenon. Here, we hypothesized that spindle trains are more likely when SOs co-occur in the prefrontal and motor cortex. We conducted simultaneous neural recordings in the medial prefrontal cortex (mPFC) and primary motor cortex (M1) of male rats training on the reach-to-grasp motor task. We found that intracortically recorded M1 spindles are organized into distinct temporal clusters. Notably, the occurrence of temporally precise SOs between mPFC and M1 was a strong predictor of spindle trains. Moreover, reactivation of awake task patterns is much more persistent during spindle trains in comparison with that during isolated spindles. Together, our work suggests that the precise coupling of SOs across mPFC and M1 may be a potential driver of spindle trains and persistent reactivation of motor memory during NREM sleep.

It is well established that holding information in working memory (WM) elicits sustained stimulus-specific patterns of neural activity. Nevertheless, here we provide evidence for a distinct class of neural activity that tracks the number of individuated items in working memory, independent of the type of visual features stored. We present two EEG studies of young adults of both sexes that provide robust evidence for a signal tracking the number of individuated representations in working memory, regardless of the specific feature values stored. In Study 1, subjects maintained either colors or orientations across separate blocks in a single session. We found near-perfect generalization of the load signal between these two conditions, despite being able to simultaneously decode which feature had been voluntarily stored. In Study 2, participants attended to two features with very distinct cortical representations: color and motion coherence. We again found evidence for a neural load signal that robustly generalized across these distinct visual features, even though cortically disparate regions process color and motion coherence. Moreover, representational similarity analysis provided converging evidence for a content-independent load signal, while simultaneously showing that unique variance in EEG activity tracked the specific features that were stored. We posit that this load signal reflects a content-independent "pointer" operation that binds objects to the current context while parallel but distinct neural signals represent the features that are stored for each item in memory.

On the occasion of the fifth anniversary of the Paris Agreement, the event will highlight the key role of the agricultural sectors in supporting the Paris Agreement. The Paris Agreement, [...]

Aerial America: Wilderness premieres Sunday, Sept. 7 at 9PM ET/PT

Lonnie Bunch, the director of the National Museum of African American History and Culture, discusses the Martin Luther King, Jr. memorial, one of America's greatest monuments.

In a 11-4 vote, the City Council decided to remove the 65-foot-tall monument from its location in the heart of the city

"A Soldier's Journey," a 58-foot-long bronze artwork depicting vivid scenes from the war, was illuminated for the first time at a ceremony on September 13

Scientists have created "a form of information immortality" meant to instruct future species on how to recreate humans. But who, or what, will find it?

The L'nu Sipuk Kina'muokuom school observed Indigenous Veterans Day with an event on Friday. Students, faculty and staff got together to honour Mi’kmaw military veterans and RCMP members.

Trevor Lewis was a corporal in the Canadian Armed Forces who tried to bury the memories from his deployment in Afghanistan. They all came back in 2021 after the fall of Kabul. This story is how he made peace with his time in that country.

Lloyd Gates is one of the few surviving Second World War veterans on Prince Edward Island. He recounts the highs and lows of his wartime service in Holland and France.

Here’s how Hamilton and other cities in the area are marking Remembrance Day this year.

Logos Hope :: A tribute to Clive Musendami

Penn State Shenango hosts the 13th annual Dr. Jane A. Williams Memorial 5K run/1 mile walk on campus on Saturday, Oct. 12.

Ashleigh McDonald, a doctoral student and graduate assistant in the College of the Liberal Arts’ Department of Communication Arts and Sciences, traveled to Sydney, Australia, to conduct research for her dissertation at two prominent and allegedly haunted sites that date back to the late 1700s, when Great Britain and Ireland first started using the country as a penal colony.

A study from NYU reveals that kidney and nerve cells can perform memory-like functions, suggesting memory capabilities are not restricted to the brain. By replicating a spaced learning process, scientists observed memory gene activation in these non-neural cells, expanding possibilities for enhancing learning and treating memory-related health issues.

The Office of Veterans Services and the Delaware Commission of Veterans Affairs have scheduled two events in observance of Memorial Day. As in previous years, OVS and the Commission will host ceremonies on separate days. The first will take place on Saturday, May 28, 2022, at the Delaware Veterans Memorial Day Cemetery in Bear. The […]

The Office of Veterans Services (OVS) and the Delaware Commission of Veterans Affairs (DCVA) have scheduled two events in observance of Memorial Day. As in previous years, OVS and DCVA will host ceremonies on separate days. The first will take place on Saturday, May 27, 2023, at the Delaware Veterans Memorial Ceremony in Bear, Delaware. […]

New lobby exhibit celebrates “things that aren’t there anymore” Do you remember rocking at the Stone Balloon; enjoying a muskrat meal at The Wagon Wheel; or having a shopping spree at Wanamaker’s?  If you don’t the Delaware Public Archives does. Starting in April 2024, the DPA will kick off a celebration and remembrance of things […]

WILMINGTON, Del. – Governor John Carney on Tuesday released the following statement on the Christina Board of Education’s vote to approve a Memorandum of Understanding to invest in Christina’s Wilmington schools: “Thank you to the members of the Christina Board for their important vote tonight on this MOU. This is just a first step, but […]

In observance of Worker’s Memorial Day, the Delaware Department of Labor’s (DOL) Office of Safety and Health Consultation is proud to announce the launch of SafeDE (pronounced Safe-DEE-EEE). This groundbreaking initiative signifies our dedication to enhancing workplace safety throughout Delaware, honoring the memory of workers who have tragically lost their lives on the job. SafeDE […]

DOVER, Del. (April 22, 2024) – The Delaware Forest Service hosted the Daughters of the American Revolution (DAR), Col. John Haslet Chapter in Dover, and other volunteers to establish a memorial plot dedicated to former State Forester Walter F. Gabel, who served in this role from 1974 to 1991. “We are excited about this DAR […]

Friday, May 15 is Peace Officers Memorial Day. On this day we pay tribute to peace officers across our country who have died, or who have been disabled in the line of duty. In accordance with federal law (36 U.S.C. 175) and a proclamation issued by President Trump, Governor Carney requests that the Delaware and […]

On Memorial Day, we pay tribute to those fallen heroes who have died while protecting our country. To honor the dedication and service of all of our service members Governor Carney requests that the proper protocol for the U.S. Flag Code be followed this Memorial Day. Flags are to be lowered to half-staff on Monday […]

Everyday across Delaware, thousands of firefighters serve their communities and protect the public by responding to not only fires but almost any emergency situation. Sunday, October 4 has been recognized by Congress as the day US and State flags are to be flown at half-staff in recognition of the National Fallen Firefighters Memorial Day. Governor […]

President Biden ordered flags at all U.S. government buildings and facilities to be flown at half-staff until sunset on February 26, 2021 in memory of the more than 500,000 Americans who have died from COVID-19. In concurrence with the President’s order, Governor Carney has ordered both the U.S. and Delaware flags at state buildings and […]

In recognition of Memorial Day, President Biden has proclaimed May 31, 2021, as a day of prayer for permanent peace, and designated the hour of 11:00 AM as a time when we might collectively unite in prayer and reflection. President Biden has also asked that all Americans observe the National Moment of Remembrance beginning at […]

Governor Carney and Lieutenant Governor Hall-Long join family, friends and Delawareans across our state in paying tribute to the extraordinary life and service of Second Lieutenant George M. Johnson. In recognition, the Delaware flag will be lowered to half-staff on Saturday, October 2, 2021.

In observance of the 40th National Fallen Firefighters Memorial Service and in accordance with Public Law 107-51, Governor Carney has ordered both the American and Delaware flags be lowered to half-staff on Sunday, October 3, 2021 from sunrise to sunset.

As a mark of respect for the passing of General Colin L. Powell and in recognition of his tremendous life of service to this nation, President Biden has ordered that the U.S. flag be immediately flown at half-staff until sunset on October 22, 2021. In concurrence with the President’s order, Governor Carney has ordered both […]

As a mark of respect for the passing of Madeleine Korbel Albright, the first female U.S. Secretary of State, and in recognition of her tremendous life of service to this nation, President Biden has ordered that the U.S. flag be immediately flown at half-staff until sunset on March 27, 2022. In concurrence with the President’s order, Governor Carney has ordered both the U.S. and Delaware flags at state buildings and facilities be flown at half-staff.

Strategic enhancements to the pedestrian safety campaign leverage grassroots influence and broad communications reach throughout Delaware DOVER, DE. (May 27, 2021) — This Memorial Day, The Delaware Office of Highway Safety (OHS) is bringing back its “Walk Smart, Arrive Alive” campaign — with a few additions designed to expand its reach and impact on some of the […]

Flags are ordered to fly half-staff until sunset on May 15th.

The Office of Veterans Services (OVS) and the Delaware Commission of Veterans Affairs (DCVA) have scheduled two events in observance of Memorial Day. As in previous years, OVS and DCVA will host ceremonies on separate days. The first will take place on Saturday, May 25, 2024, at the Delaware Veterans Memorial Ceremony in Bear, Delaware. […]

Read the in depth Review of CORSAIR DOMINATOR PLATINUM RGB First Edition DDR5 DRAM Memory Kit PC Components. Know detailed info about CORSAIR DOMINATOR PLATINUM RGB First Edition DDR5 DRAM Memory Kit configuration, design and performance quality along with pros & cons, Digit rating, verdict based on user opinions/feedback.

The generative AI market is experiencing rapid growth, driven by the increasing parameter size of Large Language Models (LLMs). This growth is pushing the boundaries of performance requirements for training hardware within data centers. For an in-depth look at this, consider the insights provided in "HBM3E: All About Bandwidth". Once trained, these models are deployed across a diverse range of applications. They are transforming sectors such as finance, meteorology, image and voice recognition, healthcare, augmented reality, high-speed trading, and industrial, to name just a few.

The critical process that utilizes these trained models is called AI inference. Inference is the capability of processing real-time data through a trained model to swiftly and effectively generate predictions that yield actionable outcomes. While the AI market has primarily focused on the requirements of training infrastructure, there is an anticipated shift towards prioritizing inference as these models are deployed.

The computational power and memory bandwidth required for inference are significantly lower than those needed for training. Inference engines typically need between 300-700GB/s of memory bandwidth, compared to 1-3TB/s for training. Additionally, the cost of inference needs to be lower, as these systems will be widely deployed not only in data centers but also at the network's edge (e.g., 5G) and in end-user equipment like security cameras, cell phones, and automobiles.

When designing an AI inference engine, there are several memory options to consider, including DDR, LPDDR, GDDR, and HBM. The choice depends on the specific application, bandwidth, and cost requirements. DDR and LPDDR offer good memory density, HBM provides the highest bandwidth but requires 2.5D packaging, and GDDR offers high bandwidth using standard packaging and PCB technology.

The GDDR7 standard, announced by JEDEC in March of this year, features a data rate of up to 192GB/s per device, a chip density of 32Gb, and the latest data integrity features. The high data rate is achieved by using PAM3 (Pulse Amplitude Modulation) with 3 levels (+1, 0, -1) to transmit 3 bits over 2 cycles, whereas the current GDDR6 generation uses NRZ (non-return-to-zero) to transmit 2 bits over 2 cycles.

GDDR7 offers many advantages for AI Inference having the best balance of bandwidth and cost. For example, an AI Inference system requiring 500GB/s memory bandwidth will need only 4 GDDR7 DRAM running at 32Gbp/s (32 data bits x 32Gbp/s per pin = 1024Gb/s per DRAM). The same system would use 13 LPDDR5X PHYs running at 9.6Gbp/s, which is currently the highest data rate available (32 data bits x 9.6Gb/s = 307Gb/s per DRAM).

Cadence stands at the forefront of AI inference hardware support, being the first IP company to roll out GDDR7 PHYs capable of impressive speeds up to 36Gb/s across various process nodes. This milestone builds on Cadence's established leadership in GDDR6 PHY IP, which has been available since 2019. The company caters to a diverse client base spanning AI inference, graphics, automotive, and networking equipment.

While GDDR7 continues to utilize standard PCB board technology, the increased signal speeds seen in GDDR6 (20Gbp/s) and now GDDR7 (36Gb/s) calls for careful attention with the physical design to ensure optimized system performance. In addition to providing the PHY, Cadence also offers comprehensive PCB and package reference design, which are essential in helping customers achieve optimal signal and power integrity (SI/PI) for their systems.

Cadence is dedicated to ensuring customer success beyond just providing hardware. They provide expert support in SI/PI, collaborating closely with customers throughout the design process. This approach ensures that customers can benefit from Cadence's expertise in navigating the complexities of high-speed design and achieving optimal performance in their AI inference systems.

As the AI market continues to advance, Cadence remains at the forefront by offering a comprehensive memory IP portfolio tailored for every segment of this dynamic market. From DDR5 and HBM3E, which cater to the intensive demands of training in servers and high-performance computing (HPC), to LPDDR5X designed for low-end inference at the network edge and in consumer devices, Cadence's offerings cover a wide range of applications.

Looking to the future, Cadence is dedicated to innovating at the forefront of memory system performance, ensuring that the evolving needs of AI training and inference are met with the highest standards of excellence. Whether it's pushing the boundaries with GDDR7 or exploring new technologies, Cadence is dedicated to driving the AI revolution forward, one breakthrough at a time.

Learn more about Cadence GDDR7 PHY

Learn more about Cadence Simulation VIP for GDDR7.

With the DRAM fabrication advancing from 1x to 1y to 1z and further to 1a, 1b and 1c nodes along with the DRAM device speeds going up to 8533 for Lpddr5/8800 for DDR5, Data integrity is becoming a really important issue that the OEMs and other users have to consider as part of the system that relies on the correctness of data being stored in the DRAMs for system to work as designed.

It’s a complicated problem that requires multiple ways to deal with it.

Traditionally one of the main approaches to deal with data errors is to rely on the ECC. ECC requires additional memory storage in which the ECC codes will calculated and stored at the time of memory write to DRAM. These codes will be read back along with the memory data during to the reads and checked against the data to make sure that there are no errors. Typical ECC schemes use Hamming code that provide for single bit error correction and double bit error detection per burst. Also, while several of previous generation of DRAM required Host to keep aside system memory for ECC storage latest DRAMs like Lpddr5 and DDR5 support on die ECC as part of the normal DRAM function that can be enabled using mode registers. DDR5 further requires Host to run through an ECC Error Check and Scrub (ECS) cycle on an average every tECSint time (Average Periodic ECS Interval) to prevent data errors.

Not meeting the DRAM Refresh requirement is a major reason that can lead to loss of data. This could be challenging as the PVT variation can cause the refresh requirement to change over time. Putting the DRAM in Self Refresh mode can help off-loading Refresh tracking responsibilities to DRAM but may prevent Host to do other scheduling optimizations and should be carefully considered.

Some of the other things that can affect the DRAM data are

1. Row hammer where same or adjacent rows are activated again and again leading to loss or changing of data contents in the rows that has not being addressed. Latest DRAMs like Lpddr5/Ddr5 support Refresh Management (including DRFM and ARFM) that allows the Host to compensate for these problems by issuing dedicated RFM commands helping DRAMs deals with potential Data loss issues arising out of Row hammer attacks.
2. Device temperature is another important factor that the Host needs to be aware of and if the application requires DRAM to operate at elevated temperature. The user needs to check with DRAM Vendor on the temperature range that DRAM can still operate. Data integrity at thresholds greater than certain temperature is not assured regardless of refresh rate unless DRAM is manufactured to withstand that.
3. Loss of power to DRAM will cause DRAM to lose all its contents. If this is a real concern for the system designer, they should consider using NVDIMM-N devices which has an onchip controller and a power source which is just enough to allow the DRAM contents to be copied into a backup non-volatile memory before power is lost. When the power is stored back, the stored memory contents in the non-volatile memory will be written back to the DRAM and system can continue to operate as it was before the power loss event occurred.

For transmissions and manufacturing errors DRAMs support additional features like CRC, DFE, Pre-Emphasis and PPR which will be covered in the next blog.

Cadence MMAV VIPs for DDR5/DDR5 DIMM and LPDDR5 are compressive VIP solutions and supports all of the above-listed Data integrity features including support for ECC error injection and SBE correction/DBE detection to assist with the verification challenges dealing with data integrity issues.

More information on Cadence DDR5/LPDDR5 VIP is available at Cadence VIP Memory Models Website.

Shyam 

The application of real-time data processing or responsiveness is crucial, such as in high-performance computing, data centers, or applications requiring low-latency data transfers. It enables efficient use of PCIe bandwidth and resources by intelligently managing memory write operations based on system dynamics and workload priorities. By effectively leveraging Deferrable Memory Write [DMWr], Devices can achieve optimized performance and responsiveness, aligning with the evolving demands of modern computing applications.

What Is Deferrable Memory Write?

Deferrable Memory Write (DMWr) ECN introduced this new memory transaction type, which was later officially incorporated in PCIe 5.0 to CXL2.0. This enhanced type of memory transaction is Deferrable Memory Write [DMWr], which flows as another type of existing Read/Write memory transaction; the major difference of this Deferrable Memory Write, where the Requester attempts to write to a given location in Memory Space using the non-posted DMWr TLP Type, it Postponing their completion of memory write transactions to improve overall system efficiency and performance, those memory write operation can be delay or deferred until other priority task complete.

The Deferrable Memory Write (DMWr) requires the Completer to return an acknowledgment to the Requester and provides a mechanism for the recipient to defer (temporarily refuse to service) the Request.

DMWr provides a mechanism for Endpoints and hosts to choose to carry out or defer incoming DMWr Requests. This mechanism can be used by Endpoints and Hosts to simplify the design of flow control, reduce latency, and improve throughput. The Deferrable Memory writes TLP format in Figure A.

(Fig A) Deferrable Memory writes TLP format.

Example Scenario

Here's how the DMWr works with a simplified example: Imagine a system with an endpoint device (Device A) and a host CPU (Device B). Device B wants to write data to Device A's memory, but due to varying reasons such as system bus congestion or prioritization of other transactions, Device A can defer the completion of the memory write request. Just follow these steps:

1. Initiation of Memory Write: Device B initiates a memory write transaction to Device A. This involves sending the memory write request along with the data payload over the PCIe physical layer link.
2. Acknowledgment and Deferral: Upon receiving the memory write request, Device A acknowledges the transaction but may decide to defer its completion. Device A sends an acknowledgment (ACK) back to Device B, indicating it has received the data and intends to complete the write operation but not immediately.
3. Deferred Completion: Device A defers the completion of the memory write operation to a later, more opportune time. This deferral allows Device A to prioritize other transactions or optimize the use of system resources, such as memory bandwidth or processor availability.
4. Completion and Response: At a later point, Device A completes the deferred memory write operation and sends a completion indication back to Device B. This completion typically includes any status updates or additional information related to the transaction.

Usage or Importance of DMWr

Deferrable Memory Write usage provides the improvement in the following aspects:

• Reduced Latency: By deferring less critical memory write operations, more critical transactions can be processed with lower latency, improving overall system responsiveness.
• Improved Efficiency: Optimizes the utilization of system resources such as memory bandwidth and CPU cycles, enhancing the efficiency of data transfers within the PCIe architecture.
• Enhanced Performance: Allows devices to manage and prioritize transactions dynamically, potentially increasing overall system throughput and reducing contention.

Challenges in the Implementation of DMWr Transactions

The implementation of deferrable memory writes (DMWr) introduces several advancements and challenges in terms of usage and verification:

1. Timing and Synchronization: DMWr allows transactions to be deferred, complicating timing requirements or completing them within acceptable timing windows to avoid protocol violations. Ensuring proper synchronization between devices becomes critical to prevent data loss or corruption.
2. Protocol Compliance: Verification must ensure compliance with ECN PCIe 6.0 and CXL specifications regarding when and how DMWr transactions can be initiated and completed.
3. Performance Optimization: While DMWr can improve overall system performance by reducing latency, verifying its impact on system performance and ensuring it meets expected benchmarks is crucial.
4. Error Handling: Handling errors related to deferred transactions adds complexity. Verifying error detection and recovery mechanisms under various scenarios (e.g., timeout during deferral) is essential.

Verification Challenges of DMWr Transactions

The challenges to verifying the DMWr transaction consist of all checks with respect to Function, Timing, Protocol compliance, improvement, Error scenario, and security usage on purpose, as well as Data integrity at the PCIe and CXL.

1. Functional Verification: Verifying the correct implementation of DMWr at both ends of the PCIe link (transmitter and receiver) to ensure proper functionality and adherence to specifications.
2. Timing Verification: Validating timing constraints associated with deferring writes and ensuring transactions are completed within specified windows without violating protocol rules.
3. Protocol Compliance Verification: Checking that DMWr transactions adhere to PCIe and CXL protocol rules, including ordering rules and any restrictions on deferral based on the transaction type.
4. Performance Verification: Assessing the impact of DMWr on overall system performance, including latency reduction and bandwidth utilization, through simulation and testing.
5. Error Scenario Verification: Creating and testing scenarios to verify error handling mechanisms related to DMWr, such as timeouts, retries, and recovery procedures.
6. Security Considerations: Assessing potential security vulnerabilities related to DMWr, such as data integrity risks during deferred transactions or exposure to timing-based attacks.

Major verification challenges and approaches are timing and synchronization verification in the context of implementing deferrable memory writes (DMWr), which is crucial due to the inherent complexities introduced by deferred transactions. Here are the key issues and approaches to address them:

Timing and Synchronization Issues

1. Transaction Completion Timing:
   • Issue: Ensuring deferred transactions are completed within the specified time window without violating protocol timing constraints.
   • Approach: Design an internal timer and checker to model worst-case scenarios where transactions are deferred and verify that they are complete within allowable latency limits. This involves simulating various traffic loads and conditions to assess timing under different scenarios.
2. Ordering and Dependencies:
   • Issue: Verifying that transactions deferred using DMWr maintain the correct ordering and dependencies relative to non-deferred transactions.
   • Approach: Implement test scenarios that include mixed traffic of DMWr and non-DMWr transactions. Verify through simulation or emulation that dependencies and ordering requirements are correctly maintained across the PCIe link.
3. Interrupt Handling and Response Times:
   • Issue: Verify the handling of interrupts and ensure timely responses from devices involved in DMWr transactions.
   • Approach: Implement test cases that simulate interrupt generation during DMWr transactions. Measure and verify the response times to interrupts to ensure they meet system latency requirements.

In conclusion, while deferrable memory writes in PCIe and CXL offer significant performance benefits, their implementation and verification present several challenges related to timing, protocol compliance, performance optimization, and error handling. Addressing these challenges requires rigorous testing and testbench of traffic, advanced verification methodologies, and a thorough understanding of PCIe specifications and also the motivation behind introducing this Deferrable Write is effectively used in the CXL further. Outcomes of Deferrable Memory Write verify that the performance benefits of DMWr (reduced latency, improved throughput) are achieved without compromising timing integrity or violating protocol specifications.

In summary, PCIe and CXL are complex protocols with many verification challenges. You must understand many new Spec changes and consider the robust verification plan for the new features and backward compatible tests impacted by new features. Cadence's PCIe 6.0 Verification IP is fully compliant with the latest PCIe Express 6.0 specifications and provides an effective and efficient way to verify the components interfacing with the PCIe 6.0 interface. Cadence VIP for PCIe 6.0 provides exhaustive verification of PCIe-based IP and SoCs, and we are working with Early Adopter customers to speed up every verification stage.

More Information

• For more info on how Cadence PCIe Verification IP and TripleCheck VIP enable users to confidently verify PCIe 6.0, see our VIP for PCI Express, VIP for Compute Express Link, and TripleCheck for PCI Express
• See the PCI-SIG website for more details on PCIe in general and the different PCI standards.

DDR5 DIMM Architectures The DDR5 generation of Double Data Rate DRAM memories has experienced rapid adoption in recent years. In particular, the JEDEC-defined DDR5 Dual Inline Memory Module (DIMM) cards have become a mainstay for systems looking for high-density, high-bandwidth, off-chip random access memory[1]. Within a short time, the DIMM architecture evolved from an interconnected hierarchy of only SDRAM memory devices (UDIMM[2]) to complex subsystems of interconnected components (RDIMM/LRDIMM/MRDIMM[3]). DIMM Designs and Popular Verification Use Cases The growing complexity of the DIMMs presented a challenge for pre-silicon verification engineers who could no longer simply validate against single DDR5 SDRAM memory models. They needed to consider how their designs would perform against DIMMs connected to each channel and operating at gigahertz clock speeds. To address this verification gap, Cadence developed DDR5 DIMM Memory Models that encapsulated all of the architectural complexities presented by real-world DIMMs based on a robust, easy-to-use, easy-to-debug, and easy-to-reconfigure methodology. This memory-subsystem-in-a-single-instance model has seen explosive adoption among the traditional IP Developer and SOC Integrator customers of Cadence Memory Models. The Cadence DIMM models act as a single unit with all of the relevant DIMM components instantiated and interconnected within, and with all AC/Timing parameters among the various components fully matched out-of-the-box, based on JEDEC specifications as well as datasheets of actual devices in the market. The typical use-case for the DIMM models has been where the DUT is a DDR5 Memory Controller + PHY IP stack, and the validation plan mandated compliance with the JEDEC standards and Memory Device vendor datasheets. Unique Use Case for the DIMM Discrete Component Models Although the Cadence DIMM models have enjoyed tremendous proliferation because of their cohesive implementation and unified user API, the actual DIMM Models are built on top of powerful, flexible discrete component models, each of which was designed to stand on its own as a complete SystemVerilog UVM-based VIP. All of these discrete component models exist in the Cadence VIP Catalog as standalone VIPs, complete with their own protocol compliance checking capabilities and their own configuration mappings comprehensively modeling individual AC/Timing parameters. Because of this deliberate design decision, the Cadence DIMM Discrete Component Models can support a unique use-case scenario. Some users seek to develop IC Designs for the various DIMM components. Such users need verification environments that can model the individual components of a DIMM and allow them the option to replace one or another component with their Component Design IP. They can then validate that their component design is fully compatible with the rest of the components on the DIMM and meets the integrity of the overall DIMM compliance with JEDEC standards or Memory Vendor datasheets. The Cadence Memory VIP portfolio today includes various examples that demonstrate how customers can create DIMM “wrappers” by selecting from among the available DIMM discrete component models and “stitching” them together to build their own custom testbench around their specific Component Design IP. A Solution for Unique Component Scenarios The Cadence DDR5 DIMM Memory Models and DIMM Discrete Component Models can provide users with a flexible approach to validating their specific component designs with a fully populated pre-silicon environment. Augmented Verification Capabilities When the DIMM “wrapper” model is augmented with the Cadence DFI VIP[4] that can simulate an MC+PHY stack and offers a SystemVerilog UVM test API to the verification engineer, the overall testbench transforms into a formidable pre-silicon validation vehicle. The DFI VIP is designed as a combination of an independent DFI MC VIP and a DFI PHY VIP connected to each other via the DFI Standard Interface and capable of operating seamlessly as a single unit. It presents a UVM Sequence API to the user into the DFI MC VIP with the Memory Interface of the PHY VIP connected to the DIMM “wrapper” model. With this testbench in hand, the user can then fully take advantage of the UVM Sequence Library that comes with the DFI VIP to enable deep validation of their Component Design inside the DIMM “wrapper” model. Verification Capabilities Further Enhanced A possible further enhancement comes with the potential addition of an instance of the Cadence DIMM Memory Model in a Passive Monitor mode at the DRAM Memory Interface. The DIMM Passive Monitor consumes the same configuration describing the DIMM “wrapper” in the testbench, and thus can act as a reference model for the DIMM wrapper. If the DIMM Passive Monitor responds successfully to accesses from the DFI VIP, but the DIMM wrapper does not, then it exposes potential bugs in the DUT Components or in the settings of their AC/Timing parameters inside the DIMM wrapper. Debuggability, Interface Visibility, and Protocol Compliance One of the key benefits of the DIMM Discrete Component Models that become manifest, whether in terms of the unique use-case scenario described here, or when working with the wholly unified DDR5 DIMM Memory Models, is the increased debuggability of the protocol functionality. The intentional separation of the discrete components of a DIMM allows the user to have full visibility of the memory traffic at every datapath landmark within a DIMM structure. For example, in modeling an LRDIMM or MRDIMM, the interface between the RCD component and the SDRAM components, the interface between the RCD component and the DB components, and the interface between the SDRAM components and the DB components—all are visible and accessible to the user. The user has full access to dump the values and states of the wire interconnects at these interfaces to the waveform viewer and thus can observe and correlate the activity against any protocol violations flagged in the trace logs by any one or more of the DIMM Discrete Component Models. Access to these interfaces is freely available when using the DIMM Discrete Component Models. On the unified DDR5 DIMM Memory Models, a feature called Debug Ports enables the same level of visibility into the individual interconnects amidst the SDRAM components, RCD components, and DB components. When combined with the Waveform Debugger[5] capability that comes built-in with the VIPs and Memory Models offered by Cadence and used with the Cadence Verisium Debug[6] tool, the enhanced debuggability becomes a powerful platform. With these debug accesses enabled, the user can pull out transaction streams, chip state and bank state streams, mode register streams, and error message streams all right next to their RTL signals in the same Verisium Debug waveform viewer window to debug failures all in one place. The Verisium Debug tool also parses all of the log files to probe and extract messages into a fully integrated Smart Log in a tabbed window fully hyperlinked to the waveform viewer, all at your fingertips. A Solution for Every Scenario Cadence's DDR5 DIMM Memory Models and DIMM Discrete Component Models , partnered with the Cadence DFI VIP, can provide users with a robust and flexible approach to validating their designs thoroughly and effectively in pre-silicon verification environments ahead of tapeout commitments. The solution offers unparalleled latitude in debuggability when the Debug Ports and Waveform Debugger functions of the Memory Models are switched on and boosted with the use of the Cadence Verisium Debug tool. [1] Shyam Sharma, DDR5 DIMM Design and Verification Considerations , 13 Jan 2023. [2] Shyam Sharma, DDR5 UDIMM Evolution to Clock Buffered DIMMs (CUDIMM) , 23 Sep 2024. [3] Kos Gitchev, DDR5 12.8Gbps MRDIMM IP: Powering the Future of AI, HPC, and Data Centers , 26 Aug 2024. [4] Chetan Shingala and Salehabibi Shaikh, How to Verify JEDEC DRAM Memory Controller, PHY, or Memory Device? , 29 Mar 2022. [5] Rahul Jha, Cadence Memory Models - The Gold Standard , 15 Apr 2024. [6] Manisha Pradhan, Accelerate Design Debugging Using Verisium Debug , 11 Jul 2023.

When the Arduino Mega2560 is added to the first serial port, the dynamic memory is 2000 bytes, and when the second serial serial is added, the dynamic memory is 4000 bytes. Now I need to add the third Serial serial port. The dynamic memory is 6000 bytes. Due to the many variables in the program itself, the dynamic memory is not enough. Please help me how to save the dynamic memory?

ncsim will consume an increasing ammount of memory when a function has an output port that return an associative array which was not initialized. My simulator version is 12.10-s011.

Below is a code example to reproduce the failure. The code is inside a class (uvm_object):

function void a_function(output bit ret_val[int]);

// empty 

endfunction : get_cov

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