Who needs Intel’s Optane when you have AMD’s 3D V-Cache?
Who would have thought that the best CPU could rival the best SSD? Apparently, you can run a RAM disk on AMD’s Ryzen 3D V-Cache processors and achieve sequential read and write speeds that can even beat the fastest PCIe 5.0 SSDs.
This revelation began when our cooling expert, Albert Thomas, shared an intriguing screenshot where a RAM disk showed sequential read and write speeds of approximately 178 GB/s and 163 GB/s, respectively, in CrystalDiskMark. Notably, the results were reportedly from a RAM disk running on an AMD Ryzen 7 7800X3D processor.
Initially, there was skepticism about the claim because you would need to expose the L3 cache as a block storage device to run the CrystalDiskMark benchmark. The assumed capacity (508 MB) was also larger than the 96 MB L3 cache on the Ryzen 7 7800X3D’s 3D V-Cache. However, it seems there is a legitimate way to utilize 3D V-Cache for a RAM disk.
Nemez, a user on X (formerly known as Twitter), discovered the method. This enthusiast shared the steps to make it work back in February, but it didn’t gain much attention at the time. The results were even more impressive than Thomas’s, with sequential read and write speeds of around 182 GB/s and 175 GB/s, respectively, on a previous-generation Ryzen 7 5800X3D.
The method is based on OSFMount, a free software that allows you to create RAM disks and mount image files in different formats. Creating a RAM disk in FAT32 format sounds simple enough.
However, you need to use specific settings on CrystalDiskMark for it to work. According to Nemez, you must configure the test values to SEQ 256KB, a queue depth of 1, and 16 threads. You must also set the data fill to zero instead of random. Due to the nature of the system load, the method might not work on the first try, so you may need to run the benchmark a few times.
It’s fascinating to see enthusiasts discover new uses for AMD 3D V-Cache. While the performance data looks exceptional, it is still far from unleashing the full potential of 3D V-Cache. For example, the first-generation 3D V-Cache had a peak throughput of 2 TB/s. AMD later increased the bandwidth of the second-generation variant to 2.5 TB/s.
This experiment is cool, but it’s not practical for actual use because there is no consistent way to leverage 3D V-Cache. The method is not foolproof and sometimes requires trial and error. Furthermore, the 3D V-Cache on consumer Ryzen chips is too small to be of much help. For instance, the flagship Ryzen 9 7950X3D has only 128 MB of L3 cache. On the other hand, AMD’s EPYC processors, such as the Genoa-X with 1.3 GB of L3 cache, could be an interesting use case.
Nevertheless, we believe there is potential for both 3D V-Cache and RAM disks. It’s a clever way to combine old-school and new technology. SSDs have already made RAM disks obsolete, but perhaps a large amount of 3D V-Cache could revive them. Just imagine the possibilities if AMD embraced this idea and introduced a foolproof implementation where consumers could turn 3D V-Cache into a RAM disk with the flip of a switch.