Can this lower CPU (host) consumption?

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omarsis81
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Can this lower CPU (host) consumption?

Postby omarsis81 » Thu 23 Feb, 2017 2:19 am

I ran some benchmarks with SiSoft Sandra 99 and 2001 SE to compare PCem with real hardware, in particular CPU power.

ALU is quite close to real hard: 514 MIPS on PCem vs 498 MIPS (SOYO SY-5VD with 430VX chipset).

Now... the surprise came with the FPU: 453 MFLOPS on PCem vs 272 MFLOPS (SOYO SY-5VD with 430VX chipset).

The 453 MFLOPS is like 65% more than real hard.
453 MFLOPS is astronomical for a Pentium MMX 233! 453 is a more close result for the Pentium II 333!

My point is: since CPU emulation consumes most of the host CPU power, can the FPU emulation be reduced considerably to match real readings? That would
probably save lots of host CPU power, or... maybe I'm just talking nonsense here.

sandra2001se2.jpg
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SarahWalker
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Re: Can this lower CPU (host) consumption?

Postby SarahWalker » Thu 23 Feb, 2017 5:48 pm

Actually I'm surprised the Dhrystone score is that close.

The FPU timings probably do need to be looked at, however from memory a good chunk of Whetstone is taken up with trigonometry and exponent instructions, which are relatively uncommon outside of benchmark code (as they're pretty slow on real hardware), so fixing this benchmark probably won't have a huge impact on other software.
SarahWalker
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Re: Can this lower CPU (host) consumption?

Postby SarahWalker » Sun 18 Jun, 2017 3:07 pm

Rev 771 brings this back down to reality a bit :
pcem_sandra2001.png
pcem_sandra2001.png (252.88 KiB) Viewed 374 times

Non-MMX Pentium ratings are still a bit high, I think this is due to the lack of cache emulation rather than the actual CPU timings.
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omarsis81
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Re: Can this lower CPU (host) consumption?

Postby omarsis81 » Sun 18 Jun, 2017 10:25 pm

Great job Sarah!

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