Nov 192016

FreeBSD GMABoost logoRecently, after finding out that the old Intel GMA950 profits greatly from added memory bandwidth (see [here]), I wondered if the overclocking mechanism applied by the Windows tool [here] had leaked into the public after all this time. The developer of said tool refused to open source the software even after it turning into abandonware – announced support for GMA X3100 and X4500 as well as MacOS X and Linux never came to be. Also, he did not say how he managed to overclock the GMA950 in the first place.

Some hackers disassembled the code of the GMABooster however, and found out that all that’s needed is a simple PCI register modification that you could probably apply by yourself on Microsoft Windows by using H.Oda!s’ [WPCREdit].

Tools for PCI register modification do exist on Linux and UNIX as well of course, so I wondered whether I could apply this knowledge on FreeBSD UNIX too. Of course, I’m a few years late to the party, because people have already solved this back in 2011! But just in case the scripts and commands disappear from the web, I wanted this to be documented here as well. First, let’s see whether we even have a GMA950 (of course I do, but still). It should be PCI device 0:0:2:0, you can use FreeBSDs’ own pciconf utility or the lspci command from Linux:

# lspci | grep "00:02.0"
00:02.0 VGA compatible controller: Intel Corporation Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller (rev 03)
# pciconf -lv pci0:0:2:0
vgapci0@pci0:0:2:0:    class=0x030000 card=0x30aa103c chip=0x27a28086 rev=0x03 hdr=0x00
    vendor     = 'Intel Corporation'
    device     = 'Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller'
    class      = display
    subclass   = VGA

Ok, to alter the GMA950s’ render clock speed (we are not going to touch it’s 2D “desktop” speed), we have to write certain values into some PCI registers of that chip at 0xF0hex and 0xF1hex. There are three different values regulating clockspeed. Since we’re going to use setpci, you’ll need to install the sysutils/pciutils package on your machine via # pkg install pciutils. I tried to do it with FreeBSDs’ native pciconf tool, but all I managed was to crash the machine a lot! Couldn’t get it solved that way (just me being too stupid I guess), so we’ll rely on a Linux tool for this. Here is my version of the script, which I call I placed that in /usr/local/sbin/ for global execution:

  1. #!/bin/sh
  3. case "$1" in
  4.   200) clockStep=34 ;;
  5.   250) clockStep=31 ;;
  6.   400) clockStep=33 ;;
  7.   *)
  8.     echo "Wrong or no argument specified! You need to specify a GMA clock speed!" >&2
  9.     echo "Usage: $0 [200|250|400]" >&2
  10.     exit 1
  11.   ;;
  12. esac
  14. setpci -s 02.0 F0.B=00,60
  15. setpci -s 02.0 F0.B=$clockStep,05
  17. echo "Clockspeed set to "$1"MHz"

Now you can do something like this: # 200 or # 400, etc. Interestingly, FreeBSDs’ i915_kms graphics driver seems to have set the 3D render clock speed of my GMA950 to 400MHz already, so there was nothing to be gained for me in terms of performance. I can still clock it down to conserve energy though. A quick performance comparison using a crappy custom-recorded ioquake3 demo shows the following results:

  • 200MHz: 30.6fps
  • 250MHz: 35.8fps
  • 400MHz: 42.6fps

Hardware was a Core 2 Duo T7600 and the GPU was making use of two DDR-II/667 4-4-4 memory modules in dual channel configuration. Resolution was 1400×1050 with quite a few changes in the Quake III configuration to achieve more performance, so your results won’t be comparable, even when running ioquake3 on identical hardware. I’d post my ~/.ioquake3/baseq3/q3config.cfg here, but in my stupidity I just managed to freaking wipe the file out. Now I have to redo all the tuning, pfh.

But in any case, this really works!

Unfortunately, it only applies to the GMA950. And I still wonder what it was that was so wrong with # pciconf -w -h pci0:0:2:0 0xF0 0060 && pciconf -w -h pci0:0:2:0 0xF0 3405 and the like. I tried a few combinations just in case my byte order was messed up or in case I really had to write single bytes instead of half-words, but either the change wouldn’t apply at all, or the machine would just lock up. Would be nice to do this with only BSD tools on actual FreeBSD UNIX, but I guess I’m just too stupid for pciconf