6 ms·

If I may ask why did you get it, which reasons? I like the cool non x86 factor but it's quite expensive... EDIT: Forgot to mention the open argument which is q

by mshook 7y ago

If I may ask why did you get it, which reasons? I like the cool non x86 factor but it's quite expensive... EDIT: Forgot to mention the open argument which is quite amazing as well (I've followed what Talos does).

kop316 7y ago
I tend to buy server level hardware for my own usage. It tends to last a LOT longer. With that in mind, it was roughly comparable to what I would have paid for a comparable Intel Xeon, and I like the fact that I know all of the code that runs on it (the only code that I can't actually change is the OTP memory that it first executes when it boots up, and even then you can inspect it!).
- Avamander 7y ago
  Thanks for supporting the development of open hardware and software. Very few of us can afford to do so.
  - kop316 7y ago
    They actually came out with a Blackbird, and I have been considering getting one of them to replace my server (it runs FreeNAS, but I have gotten my Debian system to run an encrypted ZFS drive).
dragontamer 7y ago
The 18-core has decent performance. If it weren't for AMD EPYC Rome chips coming out a month ago, I would have considered a Talos II. 18-cores with 4x SMT == 72 threads per Power9. That's a lot of threads, no matter how you look at it.
- slovenlyrobot 7y ago
  That's a whole lot of SMT. Can anyone comment on how it behaves compared to hyperthreading? I'm assuming at 4x each core must have a ton more execution units to go around
  - dragontamer 7y ago
    Power9 is basically "Bulldozer done right". Each SMT4 Power9 core is incredibly fat, with 4x load/store units 4x ALUs, 2x Vector units. Bulldozer probably would have called each SMT4 core a collection of 4-cores. But only 1x divider, 1x crypto unit per SMT4 core. The chief downside to Power9 is that it only supports 128-bit vectors, and these 128-bit vectors are executed by ganging-together the ALU units. (so 4x 64-bit ALUs == 2x 128-bit vectors processed per clock tick). Compared to AMD Zen (4x 128-bit pipelines), AMD Zen 2 (4x 256-bit pipelines), and Intel Skylake-X (3x 512-bit pipelines), Power9's SIMD capabilities are tiny. Another oddity: most instructions take 2-clock ticks to execute, even simple instructions like XOR or Add. This increased latency is likely the reason why it performs so poorly with Python / PHP code. But when code is written for Power9, it works quite well. Stockfish chess seems to work extremely well on Power9, likely because Stockfish scales to many "cores" well (fully taking advantage of SMT4), and only has 64-bit operations. One more wildcard: Power9 has 10MB (!!!) L3 cache for every 2-cores. That's 90MB L3 cache on the 18-core. I presume that real-life database applications would benefit greatly from this oversized L3 cache. EDIT: It should be noted that the L3 caches serve as victim-caches of other L3 caches. So Power9 core-pair 01 can have its 10MB L3 cache serve as a "L3.1 cache" of core-pair 23. AMD Zen / Zen2 L3 cache CANNOT use this functionality. So AMD Zen2 64-core may have 128MB of L3 cache, but each core only "really" can go up to 16MB of L3 cache (because the other 112MB of L3 cache is only for other cores/module) EDIT: Also note, Power9 came out a few years ago at 14nm, while Zen2 came out on the 7nm node a month ago. I think a new 7nm Power9 update is planned, but I don't know what its timeframe is. In effect, you could have 1-program using the entire 90MB L3 cache for itself on Power9. While AMD Zen2 requires (at minimum) 8-programs, each program using only 16MB L3. This design decision is clear in the intended use of the chips: Zen2 is clearly targeted at the cloud-market, while Power9 is big-iron / databases. -------- Unfortunately, most of the benchmarks these days show that AMD EPYC / Rome is just the better overall processor. Still, 18-core Power9 is relatively cheap: a complete 18-core / 72-thread system for $4000ish: https://secure.raptorcs.com/content/TLSDS3/purchase.html https://secure.raptorcs.com/content/TLSDS3/purchase.html Cheap for Power9 anyway. AMD EPYC is also relatively cheap. You can get a 16-core / 32-thread / 32MB L3 cache AMD Ryzen 9 3950x for only $700 these days (and maybe a complete system build for only $2500).

by mshook 7y ago

kop316 7y ago

I tend to buy server level hardware for my own usage. It tends to last a LOT longer. With that in mind, it was roughly comparable to what I would have paid for a comparable Intel Xeon, and I like the fact that I know all of the code that runs on it (the only code that I can't actually change is the OTP memory that it first executes when it boots up, and even then you can inspect it!).

Avamander 7y ago
Thanks for supporting the development of open hardware and software. Very few of us can afford to do so.
- kop316 7y ago
  They actually came out with a Blackbird, and I have been considering getting one of them to replace my server (it runs FreeNAS, but I have gotten my Debian system to run an encrypted ZFS drive).

dragontamer 7y ago

The 18-core has decent performance. If it weren't for AMD EPYC Rome chips coming out a month ago, I would have considered a Talos II. 18-cores with 4x SMT == 72 threads per Power9. That's a lot of threads, no matter how you look at it.

slovenlyrobot 7y ago
That's a whole lot of SMT. Can anyone comment on how it behaves compared to hyperthreading? I'm assuming at 4x each core must have a ton more execution units to go around
- dragontamer 7y ago
  Power9 is basically "Bulldozer done right". Each SMT4 Power9 core is incredibly fat, with 4x load/store units 4x ALUs, 2x Vector units. Bulldozer probably would have called each SMT4 core a collection of 4-cores. But only 1x divider, 1x crypto unit per SMT4 core. The chief downside to Power9 is that it only supports 128-bit vectors, and these 128-bit vectors are executed by ganging-together the ALU units. (so 4x 64-bit ALUs == 2x 128-bit vectors processed per clock tick). Compared to AMD Zen (4x 128-bit pipelines), AMD Zen 2 (4x 256-bit pipelines), and Intel Skylake-X (3x 512-bit pipelines), Power9's SIMD capabilities are tiny. Another oddity: most instructions take 2-clock ticks to execute, even simple instructions like XOR or Add. This increased latency is likely the reason why it performs so poorly with Python / PHP code. But when code is written for Power9, it works quite well. Stockfish chess seems to work extremely well on Power9, likely because Stockfish scales to many "cores" well (fully taking advantage of SMT4), and only has 64-bit operations. One more wildcard: Power9 has 10MB (!!!) L3 cache for every 2-cores. That's 90MB L3 cache on the 18-core. I presume that real-life database applications would benefit greatly from this oversized L3 cache. EDIT: It should be noted that the L3 caches serve as victim-caches of other L3 caches. So Power9 core-pair 01 can have its 10MB L3 cache serve as a "L3.1 cache" of core-pair 23. AMD Zen / Zen2 L3 cache CANNOT use this functionality. So AMD Zen2 64-core may have 128MB of L3 cache, but each core only "really" can go up to 16MB of L3 cache (because the other 112MB of L3 cache is only for other cores/module) EDIT: Also note, Power9 came out a few years ago at 14nm, while Zen2 came out on the 7nm node a month ago. I think a new 7nm Power9 update is planned, but I don't know what its timeframe is. In effect, you could have 1-program using the entire 90MB L3 cache for itself on Power9. While AMD Zen2 requires (at minimum) 8-programs, each program using only 16MB L3. This design decision is clear in the intended use of the chips: Zen2 is clearly targeted at the cloud-market, while Power9 is big-iron / databases. -------- Unfortunately, most of the benchmarks these days show that AMD EPYC / Rome is just the better overall processor. Still, 18-core Power9 is relatively cheap: a complete 18-core / 72-thread system for $4000ish: https://secure.raptorcs.com/content/TLSDS3/purchase.html https://secure.raptorcs.com/content/TLSDS3/purchase.html Cheap for Power9 anyway. AMD EPYC is also relatively cheap. You can get a 16-core / 32-thread / 32MB L3 cache AMD Ryzen 9 3950x for only $700 these days (and maybe a complete system build for only $2500).