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name99

macrumors 68020
Jun 21, 2004
2,407
2,309
The techheads reading this thread might enjoy reading
https://eclecticlight.co/2023/11/27/evaluating-m3-pro-cpu-cores-1-general-performance/

As usual, Howard is more interested in understanding the chips than in getting page views, so he looks at things from a few unusual angles.
Points to note include
- once genuine frequencies are taken into account, the IPC gains look higher than zero.
(You might ask why the M3 P frequency didn't ramp to full max. Presumably the heuristics for DVFS ramping have changed slightly, though who knows how exactly. Perhaps max frequency is only engaged after a few seconds of lower frequency, on the grounds that there's no point in doubling power if the issue is saving .25 seconds of wait time?)

The "NEON" and "simd" changes are substantial and interesting.
The relevant gating code is essentially a stream of dependent FADD's. If FADD takes 3 cycles (the case for M1) then a 3GHz M1 can do 1B successive dependent FADDs, and that's in fact the case.
So how do we get to ~1.6 as fast? The best case frequency different is 4/3 which isn't enough.
My GUESS is that the latency for FADD (perhaps under some specific conditions like when a result feeds directly into the same unit so there's no waiting for the register from a common dispatch bus) FADD latency has dropped to 2.5 cycles (or more precisely something like 2 dependent FADDs in 5 cycles).
If that's the case then we expect performance to increase by something like 4/3*3/2.5=1.6.
 

throAU

macrumors G3
Feb 13, 2012
9,198
7,345
Perth, Western Australia

Cheers, I only discovered his site recently with his m1 coverage, its an invaluable resource for many things, but he's definitely a good source for real world performance info.
 

Mac Hammer Fan

macrumors 65816
Jul 13, 2004
1,328
498
CPU of the M3 Max is very good, but GPU could be better. It's a pity the number of GPU cores hasn't significantly increased. Hopefully this will be the case with the M4 Max.
 

leman

macrumors Core
Oct 14, 2008
19,517
19,664
CPU of the M3 Max is very good, but GPU could be better. It's a pity the number of GPU cores hasn't significantly increased. Hopefully this will be the case with the M4 Max.

The GPU is the biggest redesign Apple did in a decade, since they first started using shader cores of their own design. It’s a fairly impressive feat of engineering. More shader cores can come later. But even with the same core count M3’s GPU is substantially faster in pretty much every task.
 

avkills

macrumors 65816
Jun 14, 2002
1,226
1,074
CPU of the M3 Max is very good, but GPU could be better. It's a pity the number of GPU cores hasn't significantly increased. Hopefully this will be the case with the M4 Max.
I disagree and agree. I disagree because this is a laptop CPU we are talking about; and if the M3 Max can even get 1/3rd the performance of a 4090 desktop chip then that is a major win for Apple.

I agree because the M3 Ultra (if there is ever going to be such a thing) needs to be on par with 4080 performance, but closer to 4090.
 
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