![]() AMD explains that this is simply a balance between the given performance improvement and the actual implementation complexity – reminding us that particularly in the enterprise market there’s the option to use memory pages larger than your usual 4K size that are the default for consumer systems. The L2 DTLB has also remained at 2K entries which is interesting given that this would now only cover 1/4 th of the 元 that a single core sees. AMD counts this up to 72 by counting the 28-entry address generation queue. Oddly enough, the load queue has remained at 44 entries even though the core has 50% higher load capabilities. On the actual load/store units, AMD has increased the depth of the store queue from 48 entries to 64. ![]() In this regard, the new Zen3 microarchitecture should do significantly better in workloads with high memory sparsity, meaning workloads which have a lot of spread out memory accesses across large memory regions. Table-walkers are usually the bottleneck for memory accesses which miss the L2 TLB, and having a greater number of them means that in bursts of memory accesses which miss the TLB, the core can resolve and fetch such parallel access much faster than if it had to rely on one or two table walkers which would have to serially fulfil the page walk requests. AMD has improved the load to store forwarding to be ablet to better manage the dataflow through the L/S units.Īn interesting large upgrade is the inclusion of 4 additional table walkers on top of the 2 existing ones, meaning the Zen3 cores has a total of 6 table walkers. The core now has a higher bandwidth ability thanks to an additional load and store unit, with the total amount of loads and stores per cycle now ending up at 3 and 2. To be able to make sure that memory isn’t a bottleneck, AMD has notably improved the load/store part of the design, introducing some larger changes allowing for some greatly improved memory-side capabilities of the design. Zen2 and Zen3 certainly do not support it at all (see the comment of Officially, the AMD's TBM, FMA4, XOP and LWP instruction sets (previously available on the Bulldozer architecture) are not supported on all Zen architectures (see this).įor more information, you can check the AMD's manual (vol 3, rev 3.33).Section by Andrei Frumusanu The New Zen 3 Core: Load/Store and a Massive 元 CacheĪlthough Zen3’s execution units on paper don’t actually provide more computational throughput than Zen2, the rebalancing of the units and the offloading of some of the shared execution capabilities onto dedicated units, such as the new branch port and the F2I ports on the FP side of the core, means that the core does have more actual achieved computational utilisation per cycle. Indeed, multiple users reported the instruction set was working correctly (see, and ). It was certainly supported on Zen1 though it was not officially the case (not present in any AMD Zen-related document nor provided by the CPUID instruction). Like 3DNow!, the FMA4 instruction set was exclusive to AMD. It appears to be available on some Zen processors (including Zen3) but it is not clear exactly which one (it at least targets AMD Ryzen PRO processors). The alternative of AMD-V is Intel VT-x.įurthermore, the skinit instruction set (for security), which is (also) a part of AMD-V and composed of the 2 instructions SKINIT and STGI, is also AMD-specific. Moreover, AFAIK, Intel has similar instruction sets for this like for example Total Memory Encryption. That being said, such instruction are typically available only on EPYC processors and not Ryzen ones. All of this is part of AMD-V (all these abbreviations are a bit confusing). ![]() It should also support older related instruction sets like SEV-ES (Secure Encrypted Virtualization - Encrypted State) composed of the instruction VMGEXIT. It also supports the AMD-exclusive SEV-SNP instruction set (Secure Encrypted Virtualization - Secure Nested Paging) composed of 4 instructions ( PSMASH, PVALIDATE, RMPADJUST and RMPUPDATE). Zen3 also supports the SSE4a instruction set composed of 4 instructions ( EXTRQ, INSERTQ, MOVNTSD and MOVNTSS) which is not supported by Intel. Indeed, the three instructions MWAITX, MONITORX, and CLZERO are supported on AMD Zen3 and no Intel processor (yet). ![]()
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