Thinkpads Forum

Hi,

Is it possible to Dedicate a specific amount of physical memory to VRAM in GMA environment through BIOS ? This is possible in HP laptops. Is it also possible in Lenovo ThinKPads ?

Await your response.

Sandeep.

It is not possible in ThinkPads. But I think it is better to let OS decide how much VRAM should be allocated than reserve a fixed amount in BIOS. If the VRAM bothers you, try to add more ram (X61/s/t supports up to 8GB).

[quote="crazyfrog"]It is not possible in ThinkPads. But I think it is better to let OS decide how much VRAM should be allocated than reserve a fixed amount in BIOS. If the VRAM bothers you, try to add more ram (X61/s/t supports up to 8GB).[/quote]

Hi,

I understand that the OS manages the VRAM better. But, I have a notebook where I have 4 GB RAM, whereas the OS(XP) never recognizes anything more than 3 GB and hence I thought if I can dedicate 1 GB to VRAM that would be a optimum utilization of the resource.

Sandeep.

If the OS only detects 3GB, it is because the remaining 1GB has been already mapped to various devices (including the GMA).

[quote="dr_st"]If the OS only detects 3GB, it is because the remaining 1GB has been already mapped to various devices (including the GMA).[/quote]

Well,

I guess the XP is capable of only identifying 3 GB memory. Any physical memory that you add on top of 3 GB gets unidentified and hence unused by the OS.

Sandeep.

dhoundiyal1 wrote:I guess the XP is capable of only identifying 3 GB memory. Any physical memory that you add on top of 3 GB gets unidentified and hence unused by the OS.

This is not accurate.

XP 32-bit, like any 32-bit OS, is capable of addressing only 4GB of memory.

However, part of this memory HAS to be reserved for various peripheral devices such as video adapters, network adapters and others.

How much exactly is reserved depends on the configuration of the particular PC, the attached devices and the BIOS. Generally, after all the devices get memory-mapped, there will be between 2.75 and 3.5GB RAM available for the OS.

In addition to the OS limit, some older chipsets (generally every laptop chipset before Santa Rosa / 965PM/GM) have their own limitations, so even if you install a 64bit OS, you will be limited by the chipset/BIOS (3GB limit on X60, 2GB limit on X3x/X4x etc).

It depends on what video chipset you have, but AFAIK the GMA 3100 in my X61t can use no more than 256 MiB RAM. I do not have a direct source, but it's implied with Linux (my machine has 4 GiB of RAM):

$ cat /proc/mtrr
reg00: base=0x000000000 ( 0MB), size= 2048MB, count=1: write-back
reg01: base=0x080000000 ( 2048MB), size= 1024MB, count=1: write-back
reg02: base=0x0bf700000 ( 3063MB), size= 1MB, count=1: uncachable
reg03: base=0x0bf800000 ( 3064MB), size= 8MB, count=1: uncachable
reg04: base=0x100000000 ( 4096MB), size= 1024MB, count=1: write-back
reg05: base=0x13c000000 ( 5056MB), size= 64MB, count=1: uncachable
reg06: base=0x0e0000000 ( 3584MB), size= 256MB, count=1: write-combining

The last register (the write-combining one) is used as video RAM.

This makes sense—you do not need more in a laptop of this class, you'd have hit the performance limit of the graphics chipset before you ever needed more video RAM.