Haswell IGP performance
18 Aug 2013 18:29:40 UTC
Topic 197150
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In the next month or two, I'm planning to build a new system around an i7-4770k. I've read about openCL apps being written to run on the IGP; and am wondering if budgeting for them in my system's total TDP is worthwile; or if I'd be better off disabling it entirely and using the additional thermal headroom to clock the CPU higher.
Haswell IGP performance
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i ran an Intel 4770k and notices IGP performance is highly sensitive to memory bandwidth.
http://einsteinathome.org/node/197052&nowrap=true#126164
be aware this beast runs hot, don't event try to use the standard cooler if you want to try any overclocking.
some infos from my sys
used Gigabyte H87-D3H mainboard (Bios Rev F3 / F4)
yes you can OC with it but i'm not into it.
stock cooler 82 - 87C (indoor 32C)
noctua NH-U14S 60C (indoor 28C) it turns off while cpu idles, quite nice
cpu runs 3.9GHz all time regardless on any workload @1.22V
imho run a discrete gpu and turn it off except you have different plans like me.
I'll be watercooling to feed
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I'll be watercooling to feed my OC. The Intel stock cooler is nightmarish; and I don't just mean the )@*(#$()$* pushpin design used to secure it. The monkey effect on everything else does look to severe to be worthwhile unless it's possible to find a project with a very small iGP memory footprint.
In my opinion using the iGPU
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In my opinion using the iGPU is absolutely beneficial, even more so if you hand-tune things a bit. with Haswell you should be able to get well above 10k RAC from the iGPU at Einstein, for an additional 20 - 30 W (depending on settings, of course). You CPU cores can match that performance, but at far higher power consumption.
Then there's the point of choosing a proper clock speed and voltage for that iGPU. Currently I'm running my HD4000 at 1.25 GHz, i.e. 100 Mhz over stock clock, at -0.19 V - which yields relatively massive power savings over a stock configuration. It's difficult to measure directly, but I'm well below 20 W for Einstein by now.
Another side effect of running the iGPU at lower clocks (I started at 1.40 GHz) is a reduction of the performance hit other projects take, because a lower clocked iGPU simply requires less main memory bandwidth to feed.
And with Haswell there's another benefit: shifting some of the power consumption to the iGPU distributes the heat more evenly than just over the tiny cores, which should reduce CPU temperature at similar power consumption.
And running both, CPU cores and iGPU, at moderate clocks and voltages ensures that both remain in the energy efficient regime. If, on the other hand, you decide to push your CPU cores 100 or 200 MHz higher you'll require more voltage and loose efficiency, never mind the fact that you'd need about a 100% overclock to make up for the throughput lost by not using the iGPU (very rough estimate).
@Lanisa: 1.22 V is far too much for stock clock! The CPU should be able to do it at ~1.00 V, which would reduce power consumption and heat output by ~44%! You'd need some stability testing (i.e. "Intel Burn Test"), but I'd definitely try undervolting. I'm running my 3770K at 4.1 GHz and 1.03 V - far below stock voltage with an overclock.
MrS
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