Intel CPU Die Topology (opens in new tab)

(jprahman.substack.com)

58 pointsstevenzzzzzzz2y ago9 comments

9 comments

This might be a nitpick, but it seems like already the intro sentence isn't factually accurate:

> Over the past 10-15 years, per-core throughput slowed down

I assume that the author meant that the acceleration of per-core throughput over time has slowed down, not the throughput itself.

dan-robertson2y ago

Why is the rtt measured here on canon lake so asymmetric? I would have expected symmetry along the leading diagonal.

yvdriess2y ago

Speculation, but could it be because of a ring topology?

jeffbee2y ago

And why is core 0 magical on that machine?

jcranmer2y ago

IIRC, core 0 is the one that tends to service processor interrupts, which may mean that the data is unusually noisy in a way that tends to underestimate the RTT latency time.

1 more reply

_a_a_a_2y ago

> Over the past 10-15 years, per-core throughput slowed down

throughput of what?

j / k navigate · click thread line to collapse

9 comments

Cockbrand2y ago

This might be a nitpick, but it seems like already the intro sentence isn't factually accurate:

> Over the past 10-15 years, per-core throughput slowed down

I assume that the author meant that the acceleration of per-core throughput over time has slowed down, not the throughput itself.

dan-robertson2y ago

Why is the rtt measured here on canon lake so asymmetric? I would have expected symmetry along the leading diagonal.

yvdriess2y ago

Speculation, but could it be because of a ring topology?

jeffbee2y ago

And why is core 0 magical on that machine?

jcranmer2y ago

IIRC, core 0 is the one that tends to service processor interrupts, which may mean that the data is unusually noisy in a way that tends to underestimate the RTT latency time.

1 more reply

_a_a_a_2y ago

> Over the past 10-15 years, per-core throughput slowed down

throughput of what?

j / k navigate · click thread line to collapse