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> But Intel has rarely been the best in microarchitecture. When is the last time Intel was behind in microarchitecture? Ice Lake beats Zen 2, then you follow a

> But Intel has rarely been the best in microarchitecture. When is the last time Intel was behind in microarchitecture? Ice Lake beats Zen 2, then you follow all the way back through Bulldozer, where AMD was utterly outclassed, then what? K10 vs. Sandy Bridge? Zen 2 is basically a copy of Skylake, made 5 years late, that only got to compete with Skylake because Intel froze in time.

klelatti 6y ago
'Rarely' is probably overdoing it but Intel has had significant architecture mis-steps. It's been able to come back so strongly in part because of it's manufacturing leadership. Once that is gone though it will be much harder.
- Veedrac 6y ago
  AMD came back from Bulldozer.
  - klelatti 6y ago
    Not impossible, just much harder. Plus AMD has access to TSMC 7nm.
gruez 6y ago
>When is the last time Intel was behind in microarchitecture? Ice Lake beats Zen 2 I'm not sure whether you can make that conclusion just because the two products have similar performance. zen 2 has better IPC, which is a better indicator of microarchitecture than raw performance. In the case of Intel, the only reason they're still ahead is because of the high clocks from a very refined 14nm process. >Zen 2 is basically a copy of Skylake Source for this?
- Veedrac 6y ago
  > zen 2 has better IPC Ice Lake has better IPC. The only issue with Ice Lake is that it's on a broken 10nm process, which primarily means that clocks are terrible. > Source for this? https://en.wikichip.org/wiki/intel/microarchitectures/skylake_(client) https://en.wikichip.org/wiki/intel/microarchitectures/skylak... https://en.wikichip.org/wiki/amd/microarchitectures/zen_2 https://en.wikichip.org/wiki/amd/microarchitectures/zen_2 Both have a 224 entry ROB, 92 vs. 97 entry scheduler, 180 entry PRF, 168 vs. 160 FP PRF, same number of integer ALUs, similar load/store width, 72 in-flight loads, 56 vs. 48 in-flight stores, etc. Consequently they perform within margins of each other. They're about as minimally different as competitors' products can be. Contrast to something like Arm's or Apple's cores, which are qualitatively different products, both to each other and to any of Intel or AMD's chips.
  - gruez 6y ago
    >Ice Lake has better IPC. my apologies, got the lake names mixed up. >Both have a 224 entry ROB, 92 vs. 97 entry scheduler, 180 entry PRF, 168 vs. 160 FP PRF, same number of integer ALUs, similar load/store width, 72 in-flight loads, 56 vs. 48 in-flight stores, etc. They have similar metrics, that doesn't mean they're copies of each other. The underlying designs are most certainly different (eg. chiplet vs monolithic). The reason they have similar in those metrics is probably due to convergent design, ie. these combination of functional units provide the best performance to transistor ratio. You see this in nature too. eg. https://en.wikipedia.org/wiki/Convergent_evolution#Opposable_thumbs https://en.wikipedia.org/wiki/Convergent_evolution#Opposable..., which look similar at a high level, but are actually different in implementation.
    - Veedrac 6y ago
      AMD's previous design was its own thing. Arm's and Apple's designs are their own things. There's still flexibility in how to build a core. Skylake is clearly not even the optimal target; Apple's approach easily outclasses it, for instance. And yet AMD did none of that; they build a core that is practically just Skylake, with no real innovation I can spot anywhere. There's nothing wrong with this as a strategy. AMD's own designs were performing pretty badly and Skylake was a straightforward, reliable target that would lead them back to competitiveness. Their uncore is plenty innovative, given their willingness to compete on scale. But a rose is a rose is a rose. Zen 2 is arguably more similar to Skylake than Ice Lake is to Skylake.

klelatti 6y ago

'Rarely' is probably overdoing it but Intel has had significant architecture mis-steps. It's been able to come back so strongly in part because of it's manufacturing leadership. Once that is gone though it will be much harder.

Veedrac 6y ago
AMD came back from Bulldozer.
- klelatti 6y ago
  Not impossible, just much harder. Plus AMD has access to TSMC 7nm.

gruez 6y ago

>When is the last time Intel was behind in microarchitecture? Ice Lake beats Zen 2 I'm not sure whether you can make that conclusion just because the two products have similar performance. zen 2 has better IPC, which is a better indicator of microarchitecture than raw performance. In the case of Intel, the only reason they're still ahead is because of the high clocks from a very refined 14nm process. >Zen 2 is basically a copy of Skylake Source for this?

Veedrac 6y ago
> zen 2 has better IPC Ice Lake has better IPC. The only issue with Ice Lake is that it's on a broken 10nm process, which primarily means that clocks are terrible. > Source for this? https://en.wikichip.org/wiki/intel/microarchitectures/skylake_(client) https://en.wikichip.org/wiki/intel/microarchitectures/skylak... https://en.wikichip.org/wiki/amd/microarchitectures/zen_2 https://en.wikichip.org/wiki/amd/microarchitectures/zen_2 Both have a 224 entry ROB, 92 vs. 97 entry scheduler, 180 entry PRF, 168 vs. 160 FP PRF, same number of integer ALUs, similar load/store width, 72 in-flight loads, 56 vs. 48 in-flight stores, etc. Consequently they perform within margins of each other. They're about as minimally different as competitors' products can be. Contrast to something like Arm's or Apple's cores, which are qualitatively different products, both to each other and to any of Intel or AMD's chips.
- gruez 6y ago
  >Ice Lake has better IPC. my apologies, got the lake names mixed up. >Both have a 224 entry ROB, 92 vs. 97 entry scheduler, 180 entry PRF, 168 vs. 160 FP PRF, same number of integer ALUs, similar load/store width, 72 in-flight loads, 56 vs. 48 in-flight stores, etc. They have similar metrics, that doesn't mean they're copies of each other. The underlying designs are most certainly different (eg. chiplet vs monolithic). The reason they have similar in those metrics is probably due to convergent design, ie. these combination of functional units provide the best performance to transistor ratio. You see this in nature too. eg. https://en.wikipedia.org/wiki/Convergent_evolution#Opposable_thumbs https://en.wikipedia.org/wiki/Convergent_evolution#Opposable..., which look similar at a high level, but are actually different in implementation.
  - Veedrac 6y ago
    AMD's previous design was its own thing. Arm's and Apple's designs are their own things. There's still flexibility in how to build a core. Skylake is clearly not even the optimal target; Apple's approach easily outclasses it, for instance. And yet AMD did none of that; they build a core that is practically just Skylake, with no real innovation I can spot anywhere. There's nothing wrong with this as a strategy. AMD's own designs were performing pretty badly and Skylake was a straightforward, reliable target that would lead them back to competitiveness. Their uncore is plenty innovative, given their willingness to compete on scale. But a rose is a rose is a rose. Zen 2 is arguably more similar to Skylake than Ice Lake is to Skylake.