He is no Jim Keller, and the mostly[1] automated transcript makes it read cringe, but it is not at all devoid of content.
Some examples of very interesting, non-obvious content:
* Even if store ports are kept fixed (2 in his example), adding store address generators (up to 4 in his example) actually improves performance, because it frees up load port dependencies.
* Within the same core, they use two different styles of load/address address contention mechanisms which he describes as two tables, one with explicit "allows" and the other one with explicit "denies" -- which of course end up converging (I understand it refers to two different encodings which vary in what is stored).
* Between cores, they have completely separate teams which reach different designs for things like this.
* It was interesting to me to discover how isolated the different core design teams work (which makes sense)
* It was interesting to me to picture the load/store address contention subsystem, which must be quite complex and needs to be really fast.
And I stop listing, re different types of workloads, gaming workloads being similar to DB workloads, and even more similar between them than to SPEC benchmarks and so on.
Just go read the interview if you're interested in CPU design!
[1] mostly automated: at least the dialog name labels seem to be hand-edited, as one of them has a typo
I asked chatgpt to give a contentful summary of the interview, it seems to be more or less accurate, albeit surface level. If anyone is interested.
It gets the "why" but not the "how". Maybe someone here can prompt it further to speculate on the "how". I don't think I'll be able to verify its output well enough to do that.
brucehoult|4 months ago
"We made it wider and deeper".
Gosh. Why didn't anyone think about doing that before?
jng|4 months ago
Some examples of very interesting, non-obvious content:
* Even if store ports are kept fixed (2 in his example), adding store address generators (up to 4 in his example) actually improves performance, because it frees up load port dependencies. * Within the same core, they use two different styles of load/address address contention mechanisms which he describes as two tables, one with explicit "allows" and the other one with explicit "denies" -- which of course end up converging (I understand it refers to two different encodings which vary in what is stored). * Between cores, they have completely separate teams which reach different designs for things like this. * It was interesting to me to discover how isolated the different core design teams work (which makes sense) * It was interesting to me to picture the load/store address contention subsystem, which must be quite complex and needs to be really fast.
And I stop listing, re different types of workloads, gaming workloads being similar to DB workloads, and even more similar between them than to SPEC benchmarks and so on.
Just go read the interview if you're interested in CPU design!
[1] mostly automated: at least the dialog name labels seem to be hand-edited, as one of them has a typo
saagarjha|4 months ago
misja111|4 months ago
porridgeraisin|4 months ago
I asked chatgpt to give a contentful summary of the interview, it seems to be more or less accurate, albeit surface level. If anyone is interested.
It gets the "why" but not the "how". Maybe someone here can prompt it further to speculate on the "how". I don't think I'll be able to verify its output well enough to do that.
BoredPositron|4 months ago
Not a lot of novel information either.
gjvc|4 months ago
[deleted]
reitzensteinm|4 months ago
saagarjha|4 months ago
Oleh_h|4 months ago
norin|4 months ago