X1800XT Crossfire Setup Question

[Virtra]

I've been looking for the answer to this everywhere, but I just can't find it. First off I know that if you want a crossfire setup you have to have at least one of them be a crossfire edition card so that it will act as the master card, and that both cards have to have the same GPU (i.e. both X850XTs or both X1800XTs).

Here's my situation - I already have a Sapphire X1800XT w/ 256MB of RAM (only crossfire ready), and there's a crossfire edition mobo in the mail. At some point in the future I'll probably get a X1800XT crossfire edition card so I can get a bit more longevity out of my computer. However, all the current X1800XT crossfire edition cards only seem to come with 512MB of RAM. My question is this: will I be able to utilize all 768MB of memory, or is there going to be some compatability issue that prevents that from happening? I know that there are problems between pairing up an X1800XT with an X1800XL, so does anyone know if I might find myself in the midst of a similar problem, or is the fact that they're both XT's mean that I'll be fine? Thanks in advance!

 

[thilanliyan]

I think the master card changes to match the slave card so in all likelyhood it will go down to 256ram.

 

[firewolfsm]

don't get it, at high res the max it can give more than 1 card is 30%

 

[Snakexor]

Originally posted by: firewolfsm
don't get it, at high res the max it can give more than 1 card is 30%

what?

 

[Virtra]

Originally posted by: thilan29
I think the master card changes to match the slave card so in all likelyhood it will go down to 256ram.

Yeah, but that isn't always the case - you're right that in instances where the two cards have different numbers of pipes, they will both operate at the lower level... But that isn't the case when they have different clock speeds, as they will both opporate at their own individual clock speeds.

So does the RAM act more like the pipes or the clock speed?

 

[Golgatha]

Neither, it is video memory and has nothing to do with pipes or clock speed.

 

[rbV5]

However, all the current X1800XT crossfire edition cards only seem to come with 512MB of RAM. My question is this: will I be able to utilize all 768MB of memory, or is there going to be some compatability issue that prevents that from happening?

To enable Crossfire with the 256 MB X1800 XT or X1800 XL using a 512 MB Crossfire Editon master card, you must enable it in the drivers and reboot inorder to disable 256 MB of the Master Cards Ram.

With the XL, in Crossfire the Master Card will also disable 4 pipelines as well. Clockspeeds are unaffected in either case.

With Crossfire disabled, the Crossfire Editon is the Master card, and you'll have to reboot in order to enable the extra 256MB of vram.

 

[thilanliyan]

Originally posted by: rbV5
With the XL, in Crossfire the Master Card will also disable 4 pipelines as well. Clockspeeds are unaffected in either case.

huh??? The XL ALSO has 16 pipes doesn't it?? You're talking about the GTO???

 

[Virtra]

Originally posted by: rbV5To enable Crossfire with the 256 MB X1800 XT or X1800 XL using a 512 MB Crossfire Editon master card, you must enable it in the drivers and reboot inorder to disable 256 MB of the Master Cards Ram.

Well that sucks... hopefully I can still exchange the card that I have now. Well, thanks for the heads up anyway.

Originally posted by: thilan29

Originally posted by: rbV5
With the XL, in Crossfire the Master Card will also disable 4 pipelines as well. Clockspeeds are unaffected in either case.

huh??? The XL ALSO has 16 pipes doesn't it?? You're talking about the GTO???

You're right, the XL also has 16 pipes; its the GTO that has 12.

 

[AzNPinkTuv]

sell them both and get a 1900xtx

 

[Virtra]

Since I've only bought one, it would be hard to sell them both. The only reason that I want a dual card solution in the first place is so that in a year or year ans a half from now I can buy the 2nd card for cheap and increase the longevity of my computer. I AIN'T MADE OF CASH, YO!!!

But speaking of which, which card will depreciated more in total value over time? Does it make more sense to buy the Crossfire Edition card now and buy the regular X1800XT later, or the regular X1800XT now and the Crossfire Edition card later? Seems like a coin flip, almost, because the CF Edition is priced higher, but will probably also retain its value more than the regular X1800XT. If anyone has walked down this path before, I'd be greatful for some first hand advice.

 

[rbV5]

Originally posted by: thilan29

Originally posted by: rbV5
With the XL, in Crossfire the Master Card will also disable 4 pipelines as well. Clockspeeds are unaffected in either case.

huh??? The XL ALSO has 16 pipes doesn't it?? You're talking about the GTO???

Sorry, yes...LOL, the point I was making was that the pipelines would be disabled to match the slave card (I know better since I do also own an x1800XL also Doh!)

I don't know how long x1800 cards will last, and Crossfire Editon is much harder to find. I got mine used, so you might try watching for them in FS/T. One real problem with Crossfire and SLI both, is the lack of support for different cores, I wouldn't expect a Crossfire Editon card to be readily available a year after availability.