Red Hat Bugzilla – Bug 111590
correct amount of video memory not detected w/ Intel 865G chipset
Last modified: 2007-11-30 17:06:59 EST
Description of problem: Only 832kb of video memory is detected regardless of amount in card and/or BIOS settings. Neither the base driver, nor the driver from http://www.intel.com/support/graphics/linux/ solved the problem. kernel-2.4.21-4.EL && XFree86-4.3.0-35.EL How reproducible: Always Steps to Reproduce: 1. Install on Dell Optiplex GX270 2. startx 3. Additional info: The Dell Optiplex GX270 has embeded Intel Extreme Graphics 2 video which uses the 865G chipset.
This is not a video driver bug or XFree86 bug. This is a bug in the video BIOS itself. Intel integrated video hardware uses a UMA (Unified Memory Architecture) in which the main system memory is shared with the video device. This memory is referred to as "stolen" memory, and the amount of memory that gets stolen is determined by the video BIOS at system POST time. A BIOS which was implemented properly to Intel's specifications, allows this value to be configured by the user in the CMOS setup screen or equivalent feature, however some manufacturers violate Intel's specification and do not allow this value to be changed in their CMOS setup. The Intel developer website has information on this BIOS misimplementation problem, and this has been a cause of problem for Linux users for quite some time now, in particular on Dell laptops and other Dell hardware. The XFree86 video driver is limited to using the amount of memory that the system has configured the video device to use, and no more than that. Your BIOS has configured the video adaptor to have only 832Kb of memory available, and so that is all XFree86 ever sees available. This problem does not happen in Microsoft Windows OS, because Intel's own video drivers know how to program the chipset directly to reprogram the amount of video memory inside the video driver, just like the BIOS does. Since Intel has the complete technical specifications for how to do this, they have no problem implementing this BIOS bug workaround in their video drivers for Windows. Intel's video hardware documentation is not available to the open source community, nor is any information on how to tweak the XFree86 i8xx video driver to bypass this limitation. As such, this BIOS firmware bug affects all users of open source operating systems, and we can not do anything about it other than wait for Intel to supply patches to the i8xx video driver to work around the issue by programming the chipset directly, or for Intel to release the specifications for their video hardware to the OSS community. If Intel does release the specificiations, then whoever investigates the problem will require physical access to the hardware in addition to the hardware specification in order to develop a workaround solution to this problem. This very same problem affected Dell laptops with i830 video in them about a year and a half ago, and it took about 8-12 months for a workaround to be implemented in XFree86, and only after the required information has been provided to the community. Closing bug as NOTABUG, as this is a BIOS firmware bug in Dell systems, and not a video driver bug. Once a workaround for this problem has been made available by Intel, we can review it for potential inclusion in future OS releases, and possibly future erratum for existing releases depending on how big the changes are.
A work-around is available at: http://www.chzsoft.com.ar/855patch.html