Ubuntu показывает только 256 Мб виртуального диска, когда он должен быть 1 ГБ [дубликат]

У меня есть ATI HD6370 с выделенным 1G, работающим на Ubuntu 11.10. Ниже приведен вывод dmesg

sourajit@sourajit:/etc/X11$ sudo dmesg | grep drm
[    5.149765] [drm] Initialized drm 1.1.0 20060810
[    5.606144] [drm] radeon defaulting to kernel modesetting.
[    5.606147] [drm] radeon kernel modesetting enabled.
[    5.606436] [drm] initializing kernel modesetting (CEDAR 0x1002:0x68E4 0x17AA:0x397A).
[    5.606630] [drm] register mmio base: 0xE0600000
[    5.606631] [drm] register mmio size: 131072
[    6.475815] [drm] Detected VRAM RAM=1024M, BAR=256M
[    6.475819] [drm] RAM width 64bits DDR
[    6.475890] [drm] radeon: 1024M of VRAM memory ready
[    6.475891] [drm] radeon: 512M of GTT memory ready.

. Однако это вывод lspci, post install. Что это значит? Сколько памяти на самом деле использует radeon?

01:00.0 VGA compatible controller: ATI Technologies Inc Robson CE [AMD Radeon HD 6300 Series] (prog-if 00 [VGA controller])
    Subsystem: Lenovo Device 397a
    Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
    Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
    Latency: 0, Cache Line Size: 64 bytes
    Interrupt: pin A routed to IRQ 42
    **Region 0: Memory at c0000000 (64-bit, prefetchable) [size=256M]
    Region 2: Memory at e0600000 (64-bit, non-prefetchable) [size=128K]**
    Region 4: I/O ports at 3000 [size=256]
    Expansion ROM at e0620000 [disabled] [size=128K]