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The Impact of the AGP-Speed

Adjusting The AGP-Speed

Adjusting the system so that it would run under different AGP-speeds is a rather difficult task. It varied for almost each platform that I used.

  1. Athlon-platform with AMD750 Irongate-chipset

  2. AMD750 or 'Irongate' is supposed to offer AGP1x and AGP2x, but you are certainly aware by now that on those systems GeForce is running only at AGP1x by default. There is a switch in the driver however, which enables AGP2x on Irongate. It is an entry into the system registry of Windows 95 or Windows 98:
    [HKEY_LOCAL_MACHINE\Software\NVIDIA Corporation\Global\System]
    "EnableIrongate2x"=dword:00000001

    Setting it to '1' as above results in AGP2x-mode, removing the entry completely resets back to AGP1x. For some reason I could set this entry to '0' and AGP2x would still be running. Please don't forget to restart your system before a change in the registry is taking effect. I'd also like to note that most Irongate-systems will sooner or later hang in 3D-games if you keep AGP2x enabled.
  3. Athlon-Platform with VIA's Apollo KX133-chipset

  4. It's very nice and easy in case of this chipset, because you can switch between AGP1x, 2x and 4x within the BIOS-setup. For some reason the registry-entries mentioned below don't have any impact on the AGP-speed in case of KX133.
  5. Pentium III-Platform with Intel's 820 and 840-chipset

  6. There is another registry-entry for the GeForce-driver that impacts on the AGP-speed:
    [HKEY_LOCAL_MACHINE\Software\NVIDIA Corporation\Global\System]
    "ReqAGPRate"=dword:00000004

    Setting this entry to '4', '2' or '1' will switch between the different AGP-speeds. Somewhere on the web I found somebody proclaiming the setting '256' or hex '100' as a helpful adjustment, and I would like to advise you that this setting does only have one effect, it confuses the GeForce-driver and slows down system-performance tremendously. Again I'd like to mention that you need to restart your system before the setting takes effect and also that this setting doesn't have any influence on KX133-platforms.

Benchmark Setup

Hardware Information
CPUAMD Athlon 800, Pentium III 800EB
KX133 MotherboardVIA VT5249B1 Reference Board, BIOS date Jan 4, 2000
Irongate MotherboardGigabyte GA-7IX, BIOS Dec. 1999,Super Bypass enabledThe previously recorded Asus K7M-board without Super Bypass was not used in this test. I apologise for this mistake.
Intel 820 MotherboardAsus P3C-L, BIOS 1012 beta 3
Intel 840 MotherboardIntel OR840, BIOS OR840600.86E.0207.P02.
Memory for Athlon boards128 MB Micron/Crucial Technologies PC133 CAS2
Memory for PIII-boards2 x 64 MB Samsung PC400 RDRAM RIMMs
NetworkNetgear FA310TX
Graphics CardNVIDIA GeForce256 DDR Reference Board
Driver Information
GeForce256NVIDIA Reference Driver rev. 3.68
KX133 Chipset DriversVIA 4in1 4.19
Environment Settings
OS VersionWindows 98 SE 4.10.2222 A
DirectX Version7.0
Screen Resolution for SPECviewperf1280x1024x32
Refresh Rate for all resolutions85 Hz
SPECviewperf version6.1.1