Well,Laskos wrote: ↑Mon Jul 08, 2019 8:03 am
Not sure about what you say. With this reasoning, Uri would better buy 3000 series 32 core Threadripper with 2080ti Super.
Punctually: 12 core 3900X and 16 core 3950X.
Base clock is significantly (300MHz) higher with 12 core 3900X. I am skeptical the clocks can be equalized when the Boost is stabilized. I guess a gap of 200MHz will remain, or 5% in speed.
L2 + L3 cache size per core is significantly higher on 12 core 3900X compared to 16 core 3950X. IPCs are the same.
All in all, single core performance might be about 10% better with 12 core CPU, and that affects Leela speed, for example (and many other applications). And multi-core performance of 16 core CPU with Stockfish (NPS) is probably no more than 25% higher than that of 12 core CPU.
$750 for 3950X is pricey to my taste, actually a bit overpriced. I am replying to Uri from "a poor guy perspective" thinking of some limited budget. And spending $250+ more for a dubious all-in-all advantage of having 20% faster Stockfish, but 5% slower Leela and 10% slower single core applications is an issue for me.
First, the Threadripper 2990WX has the disadvantage of haveing only the same memory band width as the 2950X because the two extra chiplets don't have memory controllers on them. Therefore all memory access by cores on those chips must be satisfied by the infinity fabric between chips and eventually uses up bandwidth that would be available to the chip satisfying the request. So not only does each core have half the bandwidth of the 2950X half of the memory accesses will also incurs the infinity fabric latency. Even though the 2990WX has terrible memory bandwidth per core comparatively speaking, it still does relatively well for AB chess engines because they don't require a great deal of bandwidth to start with. It would be much faster for AB chess engines if all chiplets had a memory controller on them. I haven't tried to analyze the new Threadrippers yet because I have no data on them. So, determining if they would be a good buy for this application will have to wait to see what thy do with them. The could "fix" the problem with the 2990WX in the 3990WX in which case I'm pretty sure it will be the better buy depending on cost of course. We will see when the time comes.
Therefore a direct comparison between the older generation crippled 32 core cpu and the new generation non-cripped cpu is flawed.
Second, the chiplets are pre-binned by AMD before placing them into a cpu. AMD has as much as stated that the best binning chiplets will go on the higher priced SKU's such as the Ryzen 9 3950X. This means that the coolest running and fastest chiplets will be found on the 3950X. This is why thermal throttling will be less than one might expect. By adjusting the power target you can virtually guarantee that the cores will be boosted to their thermal limit. Since AMD sets the thermal limit based on boost clock and NOT base clock, arbitrarily discounting the boost clock would be a mistake. I'm not saying that you will be running all cores at the boost clock with out over-clocking. But I am saying it will not be averaging just the base clock unless it's in an adverse thermal environment. From what I've seen, with reasonably good cooling, I expect average clocks on all cores while running an AB engine to be higher than the base clock of the 3900X and it could be significantly higher. This is based on running power virus software on all cores (this draws significantly more power than ANY chess engine) and still maintaining average clocks above base clock speed.
I'm going to wait and see before I buy, but that's what I'm expecting.
I Think you are wrong on how much you discount the 16 core based on heat throttling. But time will tell. Theoretically, if you keep the CPU cool and supply enough power (e.g. increase the power target 50%) all cores can maintain boost clock indefinitely. Since the boost clock is greater on the 3950X by virtue of chiplet binning I think it will be a far superior CPU for running chess engine.
Regards,
Forrest