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Comment by rektide | Hacker News Reader

I'm mixed. Definitely a very competent chip, great perf & efficiency gains, a fairly lovely new platform.

$700 for the 16-core 7950X chip is well into HEDT price range, and while this has the CPU oomph everything else is missing. It's more $/core than what EPYC launched at, with a 16 core EPYC 7281 running $650. That had half the MHz & wasn't as good an architecture, but it also 128 lanes of PCIe (3.0 in Naples then 4.0 in Rome) and 8 channels of memory, versus 28 PCIe lanes (5.0!) / 2 channel memory (oof); that's a huge advantage.

Hopefully Intel can start shipping new process nodes again & the competition can come-back.

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The Ryzen 9 5950x launched just under two years ago at $800. This is an improvement on those prices.

The improvements in IPC over the original Zen core of the EPYC 7281 are quite substantial, and AMD is in a much better position than it was those five long years ago.

One downside is that the TDP is almost doubled (170/~230 W vs 105/140 W for default/PPT) which may be a dealbreaker - certainly for my SFF system where I'm not sure I can cope with another 100W. These are limited by the socket really (AM4/AM5), but still it's nice to have that many threads in such a low power budget. I'm more curious to see what the 32-thread competition turns out to be in the same TDP bracket.

TDP are made up numbers. Since they are arbitrary, you can't meaningfully say that they have doubled.

It's not that made up. 5950X used 120-140 W and I expect the 7950X to use 210-230 W. AMD said that the increased multicore performance comes from a higher power limit.

I’ve no doubt that the newer cpu will use more power, but the numbers are made up. They’re picked by the marketing department using a formula, and calling them “watts” to try to make them look like energy used or heat dissipated doesn’t make them real. They don’t correspond to numbers that you can actually measure in any way.

Whether or not what marketing calls it is accurate, Anandtech measure power draw in their reviews and (at least in this example) it's pretty well aligned with the advertised TDP/PPT: https://www.anandtech.com/show/15043/the-amd-ryzen-9-3950x-r...

The 105W for the 3950X doesn't include package power. Add that, and it's closer to 150W (at least for me). This is before enabling PBO.

They measured one “105W” TDP chip maxing out at 86 Watts, and another “105W” TDP chip maxing out at 144 Watts? That’s not “pretty well aligned” with anything.

See the part of the article starting at “We’ll first start with iso (like-for-like) comparisons between Ryzen generations, with iso-power.” That shows “up to +37%” at 105W.

This is true, but there can be advantages to having 32 cores over 16, depending on your workload.

I’m not sure what you’re saying. Both the 5950X and the 7950X are 16 cores/32 threads.

See my original post. I have an SFF case with a water-cooled 5950X+3090. That's already borderline for noise and thermals on a 240mm radiator, so an extra 100 W for the 7950X would probably be untenable. But as people point out - more perf per watt would probably mean cooler performance in a lot of workloads. It'll be interesting to see what the ITX options are for AM5 anyway.

Try to think of TDP as "thermal headroom." It's not efficiency or power consumption. It's room for the CPU to speed up when it's necessary. The boost max going from 4.9Ghz to 5.7Ghz (16%), and at the high end, the power necessary to increase clocks ramps up.

In another slide, they indicated ~62% lower power at the same performance levels of the Ryzen 5000 CPUs. So more efficient, but also able to clock higher and get work done faster.

For a thermally constrained system, you won't achieve the absolute maximum performance if the CPU throttles, but you do very much benefit from a more efficient architecture (+13% IPC) and process node.

So for a similar launch price you get >2x the performance, almost identical pcie bandwidth (4x28) and faster memory (less of it though). Seems pretty great to me?

It's good that AMD doubled the lanes on the PCH as 4 was a real limit (some of the higher-end motherboards have 3xM.2s plus Wifi etc hanging off the PCH, so definately a bottleneck).

8x DDR4-2666 -> 2x DDR5-5600 is half the memory throughput too. That was the first thing that made my head scratch; having much bigger cores & still lots of PCIe throughput, but way less memory bandwidth.

That said, 8x DDR4-2666 also scaled up to 64c chips in Naples, this isn't unreasonable.

But you're comparing consumer/desktop to HEDT/server. They prioritize different things - the memory bandwidth is less of a bottleneck on desktop. While your premise is that the pricing is HEDT (based on a first generation part from 2017), the current Threadripper is a $6500 part that does still carry 8 memory channels, up to 3200Mhz.

One would imagine that EPYC based on Zen 4c would have the memory throughput you crave, though I wouldn't hold your breath for $700 pricing. It's still hard to say how committed AMD is to the middle ground of HEDT.

https://www.amd.com/en/products/cpu/amd-ryzen-threadripper-p...

https://www.servethehome.com/amd-ryzen-threadripper-pro-5995...

One thing to consider is the growth of cache. If you have better L3 hitrate (which you should given the doubling of L3 cache and 10x growth of L2 cache), you ease up the memory pressure a bit.

Ryzen 9 has always been >$500 HEDT without the HEDT socket. I assume Genoa will cost even more.

imo, it's the opposite. compared to the original thread rippers, this chip has way more pcie (gen 5 vs gen3) and although it has less ram bandwidth, 64mb of l3 cache mean you don't need it as much. this costs as much as the original threadrippers did because they are the replacement for that class of chips.

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