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Old 2017-07-17, 03:03   #176
kriesel's Avatar
Mar 2017
US midwest

590910 Posts
Default First try on Intel igp of GpuOwL

GpuOwL (4M flavor) trial on an I7-7500U system

An i7-7500U is two CPU cores with hyperthreading, plus one HD620 iGP.

GpuOwL took approx 19 seconds to get started and launch the first selftest exponent.
It identified and listed 4 devices.
Zero and two are identified as 24x1050Mhz Intel(R) HD Graphics 620; OpenCL 2.1
One and three are identified as 4x2700Mhz Intel(R) Core*TM) i7-7500U CPU @ 2.70Ghz; OpenCL 2.1 (build 2)

It raises the HD620 clock rate from 300Mhz idle value to 950-1000Mhz.
Selftest cases run at iteration times of 140-145 msec/iteration.
Prime95 throughput drops by about half during this use of the iGP by GpuOwL.
(prime95 43M LL test goes from 16 msec/iteration, to 30-33msec/iteration; other prime95 worker goes from ECM on 16.9M 96 seconds per screen output to 152 seconds per output)

The 15W TDP total was not changed; but 8.4 watts of it is absorbed by the iGP, dropping cpu frequency to 1.6Ghz and lowering CPU wattage. (CPUID HWMonitor and TechPowerUp GPU-Z)
Other elements are Uncore 1.5 W, DRAM 1.6W, IA Cores 5.2W

Task Manager shows prime95 dropping from ~72% CPU load before launch of GpuOwl, to about 40% during GpuOwL operation.
This is not due to cpu load by GpuOwL. The GpuOwL process shows no cpu usage in Task Manager (occasionally a fraction of a percent).
The drop in prime95 cpu usage is assumed to be due to some combination of TDP management and contention for memory bandwidth since the iGP uses shared system RAM.

Launching a second instance of GpuOwL in a separate directory near the end of completion of the selftest (two exponents left) did not noticeably change prime95 cpu.
There was no discernible difference in HD620 clock rate or power consumption or Prime95 throughput between one and two instances. I found later that the one started earlier had been accidentally put into Select status. Once that was cleared the two instances ran simultaneously at half speed. Run times were 140-145msec/iteration with a single gpuowl running, and approx 299msec/iteration with two. So in regard to prime95, still no discernible difference between two and one instance of gpuowl after clearing the select status.

Pilot error? May try it on a different older system too.
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