What is USWC found on Asus mobos???

[AngelOfDeath]

My P3B-F have a feature called USWC (uncacheable, speculative write combining) which should increase performance, I've enabled it but don't actually know what it does. Do you know what it does???. And should I use it or not???.

AoD

 

[Shagga]

I asked this a while back AoD and couldn't get an answer other than if your Video card supports it, then it should be enabled.

 

[utopia]

this is for selected professional video-cards.

 

[AngelOfDeath]

Utopia: What cards are special selected vid-cards???.

AoD

 

[masterskartrg]

all it does is enable fast writes for agp i think you get a couple points for 3dmark

 

[AndyHui]

Nothing to do with professional video cards, nor with fastwrites or sidebanding. USWC is a feature available to Pentium Pro and later supporting chipsets (440FX, LX(EX), BX(ZX), i8xx, etc) used to speed up graphic transfers across the PCI/AGP bus. In effect, what it does is kind of caches the display data and is a form of write combining.

Does anyone remember using Fastvid?

Here is the explanation from there:

This function allows seperate writes to the banked VGA mechanism to be
combined into a cacheline that can be bursted out to video memory via the PCI
bus. I believe this used to be handled in hardware but Intel decided to make
it a programable function with the Pentium Pro to make the motherboard
architecture more general. If you enable VGAWC with FASTVID PCI throughput
will increase from 18MB/sec (B0 motherboard) to 90MB/sec for programs that
use the banked VGA mechanism (most DOS games). If you enable only VGAWC on
an early motherboard (Write Posting remains off) the bus bandwidth increases
from 8MB/sec to about 40MB/sec. Some of the newer motherboards (ASUS for
instance) have this as a BIOS setup option.

This also applies to AGP as well as PCI.

Most modern cards can handle USWC and see a small performance increase as today, most Windows drivers enable USWC as well. 3Dfx has support for USWC in their driver for the original Voodoo1.

S3 chipsets like the S3 Virge family cannot handle USWC.

 

[AngelOfDeath]

Tx AndyHui that was something I could understand . I will keep it enabled then. It's great to be able to learn a little sometimes of how to tweak the BIOS a little .

AoD

 

[utopia]

Several 3d cards support USWC, i saw this in a few manuals. I keep it disables, GF2 doesnt support it, so why bother?