ryzen 5900x or 7700

[daniel7472]

Hi all, I have a ryzen 3600, MSI Tomahawk B450 and 4x8DDR4 3200 and I have some budget for upgrade.
Switching to 5900X would be , of course, cheaper as I keep everything else but I was wondering if there is any reason to change the platform and go for AM5. Aside chess I do Autocad and PLC programming, no gaming at all.
Any advice is appreciated.

[Ras]

Switching to 5900X would be , of course, cheaper as I keep everything else but I was wondering if there is any reason to change the platform and go for AM5.

Remember that the 5900X is a 105W class while the 3600 is 65W. That's "TDP", the actual power draw is up to 88W vs. 142W. Which means that your current cooling solution will have to work quite a bit harder/louder with a 5900X, but you can configure the PPT (package power power) downwards in the BIOS, i.e. also to 88W. Otherwise, the overall performance boost doesn't seem that impressive with the 7700 over the 5900X. You do get DDR5 ofc, plus that your B450 board is limited to PCIe3. However, the RAM impact will probably not be that massive. The only case where you'd benefit from PCIe4 over PCIe3 is with a x8 GPU, but you don't even do gaming anyway.

On the other hand, you'd have to pay for a new AM5 mobo, new RAM, and do all the assembly work. In terms of raw NPS, the 7700 is a bit weaker than the 5900X because it's 8 vs. 12 cores, but fewer threads is a bit better in itself with regards to Elo, so I'd call it a wash. Plus that your current system does work (may need a BIOS update). If you auction for a used 5900X e.g. on Ebay, you'd probably get most of the bang for a fraction of the buck, compared to a full AM5 system upgrade.

[abulmo2]

Hi all, I have a ryzen 3600, MSI Tomahawk B450 and 4x8DDR4 3200 and I have some budget for upgrade.
Switching to 5900X would be , of course, cheaper as I keep everything else but I was wondering if there is any reason to change the platform and go for AM5. Aside chess I do Autocad and PLC programming, no gaming at all.
Any advice is appreciated.

The 7700 supports the avx512 instruction set, not the 5900x. If you are a programmer, chose the 7700.

[Ras]

The 7700 supports the avx512 instruction set

Wasn't the AVX512 with Zen5, aka 9700X?

[smatovic]

The 7700 supports the avx512 instruction set

Wasn't the AVX512 with Zen5, aka 9700X?

According to Wikipedia Zen 4 (Ryzen 7xxx series) has AVX-512 ISA via 2x256-bit SIMD units with four units per core:

Zen 4 is the first AMD microarchitecture to support AVX-512 instruction set extension. Most 512-bit vector instructions are split in two and executed by the 256-bit SIMD execution units internally. The two halves execute in parallel on a pair of execution units and are still tracked as a single micro-OP (except for stores), which means the execution latency isn't doubled compared to 256-bit vector instructions. There are four 256-bit execution units, which gives a maximum throughput of two 512-bit vector instructions per clock cycle, e.g. one multiplication and one addition. The maximum number of instructions per clock cycle is doubled for vectors of 256 bits or less. Load and store units are also 256 bits each, retaining the throughput of up to two 256-bit loads or one store per cycle that was supported by Zen 3. This translates to up to one 512-bit load per cycle or one 512-bit store per two cycles.[10][12][13]

https://en.wikipedia.org/wiki/Zen_4#Features

WP on Zen 5:

The vector engine in Zen 5 features 4 floating point pipes compared to 3 pipes in Zen 4. Zen 4 introduced AVX-512 instructions. AVX-512 capabilities have been expanded with Zen 5 with a doubling of the floating point pipe width to a native 512-bit floating point datapath. The AVX-512 datapath is configurable depending on the product. Ryzen 9000 series desktop processors and EPYC 9005 server processors feature the full 512-bit datapath but Ryzen AI 300 mobile processors feature a 256-bit datapath in order to reduce power consumption. AVX-512 instruction has been extended to VNNI/VEX instructions. Additionally, there is greater bfloat16 throughput which is beneficial for AI workloads.

https://en.wikipedia.org/wiki/Zen_5#Vec ... structions

--
Srdja

[smatovic]

As Rasmus mentioned, you might save some money (NPS per doillar) with the Zen 3 upgrade path, but Zen 4 has the newer AM5 socket with DDR5 and also AVX-512 instructions.

Here some recent Stockfish 16.1 benchmarks with Zen 3, Zen 4, Zen 5:

viewtopic.php?p=967471#p967471

--
Srdja

[Ras]

According to Wikipedia Zen 4 (Ryzen 7xxx series) has AVX-512 ISA via 2x256-bit SIMD units with four units per core:

Ah, the AVX512 speedup was only with Zen5, that's what I remembered, and in some AVX-heavy workloads, Zen5 provides a benefit over Zen4. Otherwise, Zen5 is pretty disappointing, especially when comparing street prices vs. Zen4, with the only interesting exception being the gaming CPU 9800X3D where the 3D cache is now on the bottom so that the cooling works better.

Here some recent Stockfish 16.1 benchmarks with Zen 3, Zen 4, Zen 5:

The 7700 doesn't really show much value over the 5900X here. Yes, you get DDR5 and AM5, but what's the point of doing a complete system upgrade if you don't get much out of it?

[smatovic]

[...]

Here some recent Stockfish 16.1 benchmarks with Zen 3, Zen 4, Zen 5:

The 7700 doesn't really show much value over the 5900X here. Yes, you get DDR5 and AM5, but what's the point of doing a complete system upgrade if you don't get much out of it?

Yes, I can agree, the Zen 3 upgrade path seems more reasonable.

--
Srdja

[daniel7472]

Thank you all for the input. I decided to go with ryzen 5950X (found one used for 220 usd) and limit the PPT so it will be safe on my MB. Probably a 85-90w will do (with the corresponding PPT limits).
Happy holidays!

[Modern Times]

Just check that your current BIOS supports the 5950X, otherwise you'll need to update it before the swap. I'm sure it probably does but worth checking.