[Bug 370552] Re: Slow flash video playback on Intel 945gm

[Robert Hooker]

Aspire ones have buggy MTRR's by default, you have to boot with
enable_mtrr_cleanup mtrr_spare_reg_nr=1 added to your grub default
options to fix it.

[    0.000000] MTRR default type: uncachable
[    0.000000] MTRR fixed ranges enabled:
[    0.000000]   00000-9FFFF write-back
[    0.000000]   A0000-BFFFF uncachable
[    0.000000]   C0000-C7FFF write-protect
[    0.000000]   C8000-EFFFF uncachable
[    0.000000]   F0000-FFFFF write-protect
[    0.000000] MTRR variable ranges enabled:
[    0.000000]   0 base 0FFFE0000 mask 0FFFE0000 write-protect
[    0.000000]   1 base 0FFFC0000 mask 0FFFE0000 uncachable
[    0.000000]   2 base 000000000 mask 0C0000000 write-back
[    0.000000]   3 base 040000000 mask 0E0000000 write-back
[    0.000000]   4 base 05F800000 mask 0FF800000 uncachable
[    0.000000]   5 base 05F600000 mask 0FFE00000 uncachable
[    0.000000]   6 base 05F500000 mask 0FFF00000 uncachable
[    0.000000]   7 base 000000000 mask 0FFFE0000 uncachable
[    0.000000] original variable MTRRs
[    0.000000] reg 0, base: 4194176KB, range: 128KB, type WP
[    0.000000] reg 1, base: 4194048KB, range: 128KB, type UC
[    0.000000] reg 2, base: 0GB, range: 1GB, type WB
[    0.000000] reg 3, base: 1GB, range: 512MB, type WB
[    0.000000] reg 4, base: 1528MB, range: 8MB, type UC
[    0.000000] reg 5, base: 1526MB, range: 2MB, type UC
[    0.000000] reg 6, base: 1525MB, range: 1MB, type UC
[    0.000000] reg 7, base: 0GB, range: 128KB, type UC
[    0.000000] WARNING: BIOS bug: VAR MTRR 7 contains strange UC entry under 1M, check with your system vendor!

with mtrr cleanup and 1 spare reg you get

reg00: base=0x000000000 (    0MB), size= 1024MB, count=1: write-back
reg01: base=0x040000000 ( 1024MB), size=  512MB, count=1: write-back
reg02: base=0x05f500000 ( 1525MB), size=    1MB, count=1: uncachable
reg03: base=0x05f600000 ( 1526MB), size=    2MB, count=1: uncachable
reg04: base=0x05f800000 ( 1528MB), size=    8MB, count=1: uncachable
reg05: base=0x060000000 ( 1536MB), size=  256MB, count=1: write-combining

so you actually get write combining for your video ram. Just edit your
/boot/grub/menu.lst and add enable_mtrr_cleanup mtrr_spare_reg_nr=1 to
your defoptions line and sudo update-grub afterwards.

-- 
Slow flash video playback on Intel 945gm
https://bugs.launchpad.net/bugs/370552
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