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Fast writes: can someone expalin this and should it be on or off

N

nealh

Diamond Member
I had a Ati 9700pro and if I recall was told to keep FW off...

well I got a BFG 6800 OC....what is performance advatange to FW and if you to lower the overclock on your videocard...is it worth it

I am running with it off for now
 
The ideology with Fast Writes: If you experience any sort of corruption or problems with graphics, disable it. If not, leave it on. As far as performance / OC gains? Slim to none.
 
Fastwrites allow GPU <-> CPU communication without touching the system memory. Leave them on unless you have problems.
 
Fast Writes was devised for performance gains, however very little if any is gained and is also sometimes lost. Fast Writes attempt this by bypassing the memory when the CPU communicates to the GPU. This increases instability. This is the reason why some people turn it off. If they notice stability problems, it is a good idea to turn Fast Writes off. If you overclock your GPU, it is a good idea to turn them off. In my opinion, Fast Writes serve no purpose and other than to increase instability, so I always keep them off.
 
I dropped four frames (from 118 to 114) in the source video stress test and couldn't figure out why ... Finally remembered that I had disabled fastwrites the last time I was tweaking my MB BIOS ... I re-enabled fastwrites and went back up to 118 ... I'm leaving it on.
 
Originally posted by: Mister Dark
I dropped four frames (from 118 to 114) in the source video stress test and couldn't figure out why ... Finally remembered that I had disabled fastwrites the last time I was tweaking my MB BIOS ... I re-enabled fastwrites and went back up to 118 ... I'm leaving it on.
Click to expand...


damn those 4 un-noticable frames!
 
i gained about 1000 points with my old 9800 pro with it on and lost that 1000 with it off in 3dmark...03 i think..
 
In general, ATI cards usually are perfectly fine with FastWrite enabled, and, in fact, it should be enabled. It's the nVidia cards that don't like FastWrite in most cases. That's what I've read a long time ago on a different board. *shrugs* Might not be true with the newer cards, but meh. Just felt like saying this. 😛
 
Originally posted by: Squally Leonharty
In general, ATI cards usually are perfectly fine with FastWrite enabled, and, in fact, it should be enabled. It's the nVidia cards that don't like FastWrite in most cases. That's what I've read a long time ago on a different board. *shrugs* Might not be true with the newer cards, but meh. Just felt like saying this. 😛
Click to expand...

That is odd because the only video card I have owned which had a problem with fastwrites was an ati 8500. Every single nvidia video card I have owned has ALWAYS worked perfectly with fastwrites enabled.
 
So far my 9700pro, 9800pro and 6800GT have worked ok with them, moreover the 9800pro would have problems with it off.
 
Originally posted by: otispunkmeyer

damn those 4 un-noticable frames!
Click to expand...


Spunkmeyer, you smug bastard! I had a digital sensor implanted in my left eye that can detect variations in plus or minus a SINGLE frame all the way up to 300 FPS! I CAN tell the difference. So before you go making JUDGEMENTS about someone you don't really know, you should remember that when you assume ...
 
Can we stop guesstimating what it is? CPU-to-GPU transfers, without putting the data in system RAM, have always been possible. The difference is that w/o FW, they're normal 66 MHz PCI cycles, whereas with FW enabled such a CPU-driven pushing of data can utilize AGP transfers at 2/4/8x that speed.

So what it does is accelerate the transfer of data (geometry, typically) that have been computed by the system CPU. Apart from when you're viewing HDTV, the amount of data isn't enough to have normal PCI cycles form a bottleneck, so normally, there is no mentionable difference.
 
Originally posted by: Peter
Can we stop guesstimating what it is? CPU-to-GPU transfers, without putting the data in system RAM, have always been possible. The difference is that w/o FW, they're normal 66 MHz PCI cycles, whereas with FW enabled such a CPU-driven pushing of data can utilize AGP transfers at 2/4/8x that speed.

So what it does is accelerate the transfer of data (geometry, typically) that have been computed by the system CPU. Apart from when you're viewing HDTV, the amount of data isn't enough to have normal PCI cycles form a bottleneck, so normally, there is no mentionable difference.
Click to expand...

Couldn't have said it better myself.

I also agree that you should leave it on unless you have problems. Some of you seem to be getting this confused with Sideband Addressing.

-Kevin
 
Speaking of which, Kevin- why does one want to turn off sideband addressing and how do you do it? I have no such option listed in my BIOS. Is it called something else? Should I use Rivatuner to shut it off?
 
Sideband addressing is either supported by your hardware or it isn't. Either the signalling of the target address works in standard PCI fashion - on the same signal lines that on the next clock start transporting data - or on their own "sideband" signals alongside the 1st data transmission.
 
Spunkmeyer, you smug bastard! I had a digital sensor implanted in my left eye that can detect variations in plus or minus a SINGLE frame all the way up to 300 FPS! I CAN tell the difference. So before you go making JUDGEMENTS about someone you don't really know, you should remember that when you assume ...
Click to expand...
lol
 
Can we stop guesstimating what it is? CPU-to-GPU transfers, without putting the data in system RAM, have always been possible. The difference is that w/o FW, they're normal 66 MHz PCI cycles, whereas with FW enabled such a CPU-driven pushing of data can utilize AGP transfers at 2/4/8x that speed.

So what it does is accelerate the transfer of data (geometry, typically) that have been computed by the system CPU. Apart from when you're viewing HDTV, the amount of data isn't enough to have normal PCI cycles form a bottleneck, so normally, there is no mentionable difference.
Click to expand...
Looking at the Nvidia's Technical Brief titled "AGP 4x With Fast Writes - A Unique Nvidia GeForce 256 Feature," I quote:

"Fast Writes capability enables the CPU to send data directly to the graphics bus without(underlined) going through the system memory."

And it also says that it accelerates all writes from CPU to GPU by this method.

There are no new benchies on Fast Writes, but old benchies seem to leave you with a bad taste in your mouth. Two people have confessed to have performance increases and that means it's doing something right. In light of this new information, I'll repeat what everyone else has been saying. Enable unless you encounter problems. If you overclock, you may benefit by turning them off, although I don't know if the performance gain will benefit.

BTW isn't PCI 33MHz and AGP is an extension of PCI that runs at twice the speed.
 
thanks for the great info...

I have them off at present and I do overclock my videocard...

I started this thread b/c when I first put together my A64 3200 and Neo2 Plat...I had at stock cpu, mobo and gpu(BFG 6800OC) major stuttering..once Iturned this off 3d mark05 seem to run fine

Funny thing is after tinkering o/cing my system and videocard(but still not up to levels on my intel P4 setup) I turned FW on and ...really didnt see much stuttering even with o/ced videocard...I ran 3dmark05 on and off essentially no difference in the score

I have not tried with games...

It may have been a bios issue with the mobo too....

so it seems it is a toss up...no major advantage seen .... hmm interesting....
 
Originally posted by: Peter
Sideband addressing is either supported by your hardware or it isn't. Either the signalling of the target address works in standard PCI fashion - on the same signal lines that on the next clock start transporting data - or on their own "sideband" signals alongside the 1st data transmission.
Click to expand...



Thanks Peter, but that doesn't really answer my question. Is sideband addressing a good thing - or not? Some people seem to suggest it is a bad thing. And whether it is supported by my hardware or not, rivatuner does provide the option of forcing it off, so I can turn it off, if I want to. Question is, what is lost/gained by doing so?
 
Yes they are a good thing in theory. THere are no real tangible performance gains. That is why you should just leave it on unless you have problems.

-Kevin
 
Originally posted by: Gamingphreek
Yes they are a good thing in theory. THere are no real tangible performance gains. That is why you should just leave it on unless you have problems.

-Kevin
Click to expand...

that makes no snese if there is no performance or benefit why turn it on and risk instabilty
 
Because it isn't always doing nothing. In some instances it does help. I believe when using large amount of AGP Aperture it can help. Addittionally the prospect that it could help when you least expect is a plus.

You aren't risking instability. Instability is not gained by turning fast writes on. SOmetimes some specific combinations of HW have trouble running with it on. So if that were to happen you would just turn it off. OC your AGP/PCI bus a little and overvolt it that will give some instability.

-Kevin
 
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