Had a reply from Gigabyte - yes, it *is* a BIOS bug, and the BIOS upgrade fixes it. The kernel bug was rejected as invalid (because it's a BIOS problem, not a kernel problem). I'll give full details below, because this wasn't quite straightfoward to fix, and hopefully it will help someone else.
1)Get the latest BIOS update from gigabyte. I used this one successfully: motherboard_bios_ga-p35c-ds3r_f4g_beta.exe 2)Extract the BIOS with wine (0.9.41 works fine). Gigabyte don't provide the md5sum, so, for info: 6f283d38e272ea433b4478f39a6cdb03 P35CDS3R.F4g 3)Copy the BIOS onto a floppy. [The manual claims that a USB key is also supported: the Q-flash utility loads the new image fine, but fails at the last step with "BIOS ID CHECK ERROR". You have to use a real old- fashioned diskette.] 4)Flash BIOS, Load optimized defaults. Enjoy. 5)Once updated, free -m reports 8002 MB free (presumably, the rest is used by the kernel). The MTRRs are now: $ cat /proc/mtrr reg00: base=0x00000000 ( 0MB), size=4096MB: write-back, count=1 reg01: base=0xe0000000 (3584MB), size= 512MB: uncachable, count=1 reg02: base=0x100000000 (4096MB), size=4096MB: write-back, count=1 reg03: base=0x200000000 (8192MB), size= 512MB: write-back, count=1 reg04: base=0xdff00000 (3583MB), size= 1MB: write-through, count=1 And the performance is about 50% better than the best it was before :-) I'm sure Gigabyte have shipped lots of boards with the original broken BIOS - is there any way to make the kernel print a warning? It would be nice if the next Ubuntu user who hits this bug can find the fix more easily! Thanks once again for your help - Richard -- kernel performance is *very* slow with 8GB RAM on AMD64. 6GB is fine. kernel 2.6.22-8 x86_64 https://bugs.launchpad.net/bugs/129172 You received this bug notification because you are a member of Ubuntu Bugs, which is the bug contact for Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
