ATI AGP cards don't support SBA?

[pigdos]

SBA = Sideband Addressing. Sisoft Sandra has never indicated SBA as being
enabled on any ATI vid-card I've ever owned (9500 Pro, 9800 Pro, X850XT).

 

[eventerke]

I'm not sure I'd trust Sandra on low-level hardware info - it reports
alot of stats wrong about my memory and other little things that I can
confirm to be as set in BIOS using other tools.

Kendt

 

[First of One]

Everest indicates SBA is enabled with my 9800 Pro. Interestingly, my Soltek
board's BIOS has no option to turn it on/off. SmartGART must have enabled it
automatically. Not that it makes a difference one way or the other...

 

[pigdos]

So SBA is irrelevant to performance? It doesn't make any difference at all?

 

[Mark C.]

So SBA is irrelevant to performance? It doesn't make any difference at all?

A few percent at most.

For what it's worth, CPU-Z shows SBA as enabled on my 9700 Pro.

Try CPU-Z instead of Sandra.

 

[First of One]

It's one of those performance-enhancing features that fails to deliver
because of flaky chipset and driver implementation. SBA may actually be
detrimental if it limits the overclockability of the video card or the
motherboard.

 

[Thomas]

Everest indicates SBA is enabled with my 9800 Pro. Interestingly, my
Soltek board's BIOS has no option to turn it on/off. SmartGART must
have enabled it automatically. Not that it makes a difference one way
or the other...

Ditto on my X800 Pro, on my LanParty 875 Pro.

 

[pigdos]

Thanks Mark, CPU-z indicates SBA is, indeed turned on for my X850XT.

 

[pigdos]

I just skimmed over the AGP 8x spec. (again). It looks like SBA is REQUIRED
for AGP 8x operation (so much for myths and rumors): "
2.3.1 AGP Transaction Requests

In the past, AGP transactions could be generated using two modes: PIPE and
SBA. The core-logic

had to support both modes, while the AGP Master could optionally use either.
AGP3.0 does not

support using PIPE mode to generate an AGP request. This leaves only the SBA
scheme, which is no

longer optional. When operating in AGP3.0 mode, the PIPE# signal pin on the
AGP connector is given

a new function, DBI-HI. A "universal" implementation must multiplex PIPE#
and DBI_HI onto the same

signal pin and select the right function based on the signaling mode of
operation."

So you can't have AGP 8x w/o SBA. Source: agp30SpecUpdate06-21.pdf.

 

[First of One]

Maybe a reason AGP 8x is unstable on my system. BF2 always crashes within
minutes of launching into a mission. It can run for hours in AGP4x mode
without problems...