nvidia and SLI

I am in the process of building a new system an I plan to have my video cards in SLI mode. My question is this: Do both card have to be exactly identical? I know that the have to be the same manufacturer and the same chipset. But do they have to have the same amount of memory? I have an evga 7950GT 256mb ordered, and I just saw the same card but with 512mb and I wanted to know if the two could be used together.

Well you are partly correct, here's what nVidia has done in the past year with their drivers:

You no longer have to have the same make/model of card, but you do have to make sure they are the same model GPU and that both have the same frame buffer size.

For example, you can have say an Asus 7900GTX 256MB or 512MB paired with a PNY 7900GTX 256MB or 512MB card.

No you can't as far as I know mix a card with 256MB with one that has 512MB of memory.

Another option you may want to consider is the 7950GX2 cards, these are essentially an SLI model with another graphics card in a daughter-board configuration.

And of course there is the latest GPU technology too, the 8800 GT/GTS/GTX models.

I'm now contimplating an upgrade as well, not that my current pair of 7800GTX's are bad, just that one of them is having some cooling fan issues and I'm not able to run SLI mode at the moment

How would I be able to tell what the frame buffer size is, or is that the amount of video ram.

Frame Buffer is the technical term for the local memory storage located on the graphics card itself

Here's another SLI question: Does windows, or linux for that matter, recognize two SLI cards as one? Kind of like two hard drives in raid mode.

In a word: no.

Well perhaps this maybe the incorrect response in that what is being asked could be mis-interpreted

To understand SLI or Crossfire technologies, you have to understand what they are attempting to do, render more information on the screen by leveraging the power of two or four indentical GPU's and outputting this information as one single display. SLI can support up to four cards while Crossfire currently only supports two graphics cards.

This isn't to say it functions like a RAID array but I guess in loose terms you could say that a pair of graphics cards in SLI or Crossfire mode is working like a RAID Zero array

Thanks for all the info. I'm just trying to keep my upgrade as painless as possible by doing the research beforehand, and asking the people who would know. That's how I learned most of the information about computers to begin with, by asking.


Bardok San

My Upgrade should be:

GIGABYTE GA-M59SLI-S5 Socket AM2

AMD Athlon 64 X2 5200+ 2.60GHz

(1)EVGA GeForce 7950 GT 256MB
(1)XFX PVT71JUHF4 GeForce 7950GT 256MB

(2) Western Digital Caviar SE WD1600JSRTL 160GB 7200 RPM 8MB Cache SATA (RAID 0)

CORSAIR XMS2 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit

APEVIA ATX-AS680W-BL ATX12V / EPS12V 680W Power Supply

SAMSUNG 16X DVD±R DVD Burner With 5X DVD-RAM Write and LightScribe

Creative Audigy Platinum eX Sound Card(Linux doesn't like X-Fi)

Microsoft Windows Vista 32-Bit Home Premium for System Builders

Mandriva Linux 2007 Powerpack

I just came across info on nVidia's web site that says that the two SLI video cards can have different amounts of memory. The only requirement is that the gpu's be the same. They even say that an overclocked gpu will work with a non overclocked gpu, but that the oc'd card will be stepped down to the speed of the non-oc'd card.

Bardok San

http://www.slizone.com/object/slizone_diy_videoguide01.html

Nice, so nVidia has updated the drivers to allow frame buffer size differences, well, that would only mean that it must ignore the extra memory on the card with more so they match up properly in SLI mode

My thinking is why would you want to mix cards this way unless you can't find another 256MB card to match up ?!?

Since both 256MB and 512MB cards are readily available, it shouldn't be an issue currently but hey, if you want to try it out then post your findings after you build the box.

The parts you are picking seem to be just fine for most gaming needs, I'm currently still running an Athlon 64-X2 4800 with 2GB of DDR400/PC3200 and a pair of WD 74GB Raptor's in RAID ZERO mode.

The only thing I would recommend to you is getting a dedicated SLI power supply instead of taking it from the main PS Unit.

I use the Thermaltake W0099 for this along with one of their ToughPower 650 Watt units for the main

I also just recently upgraded to the Cooler Master CM Stacker 830 Chassis , what a great case this happens to be, so much room and it really keeps the components cooled down...

I just looked at the Thermaltake W0099, and I just might look into getting one for myself. I just priced it at newegg.com for $56, but they're out of them for now. Do you really think I would NEED it when my 680w PS is brand new, and I don't really ever put too much of a load on my systems.

I mostly do internet surfing and listening to tunes on my computer. The only game I play on a regular basis is City of Heroes and City of Villians.

Most places, as far as I can recall, say that a SLI system needs a 550w PS or higher. Last I checked 680 is higher than 550.

I know "better safe than sorry", but that's just more $ on this upgrade. I've already spent more than I ever planned to.

Yes the old addage of better to be safe then sorry applies perfectly to this situation as well

My Thermaltake ToughPower 650 should be enough as well but I was having some random freezes and lockups.

Without changing anything other then getting one of the W0099 SLI PS Units, this resolved that issue. So it would appear that SLI mode does indeed take a lot of power to work properly, I would hazard a guess a minimum of 850 or higher is the real requirement for SLI or quad-SLI mode.

The nice thing about this unit is that if I do decide on going to quad-SLI mode I can easily add one more of these PS's into my chassis as the dual-stacked cards require (2)Two SLI power connectors per card, so you need (4)Four total power connectors.

Like I had said, I have spent more than I ever thought I would, but I have to agree that it's better if I play it safe and get one. I did happen across one at tigerdirect.com for $45, so I'll get it when I order the last few parts I need to finish this project.

I got mine at Fry's Electronics for $49.95 (USD)

Yes, you can mix the memory, but nVidia DOES NOT recommend doing so: " Can I mix and match graphics cards with different sizes of memory?
While it is not recommended, NVIDIA does offer this flexibility using Coolbits. When purchasing a second graphics card, you should try to match the memory size so that you are ensured full value and performance from your purchase. For example, if your first card is a GeForce 6600 GT with 128MB of memory, you should purchase a second GeForce 6600 GT with 128MB of memory. However, using Coolbits (value set to 18), you can force both of the cards to use the lower of the two memory sizes and operate together in SLI mode. When dissimilar memory sizes are enabled to work together using Coolbits, the effective memory size for each card becomes the smaller of the two memory sizes. Instructions to enable this feature can be found here. "

Instructions are here: mixed memory instructions

If you're mixing an OC'ed card with a slower card, I'd try OC'ing the slower card as far as possible, and see if it can do the OC'ed card's speed(s) and still be stable. If it does, and most will, you can re-write the BIOS for the slower card using NiBiTor to match the faster card's speed, and run them both OC'ed.

BTW, the guide for NiBiTor is here: NiBior Guide

Being that I'm on the east coast, there are no Fry's around here. I guess it's equal would be CompUSA, so I will see if they carry the Thermaltake W0099.

I just checked CompUSA. They carry it but they want $69.99 for it. It's cheaper online.

Here's another thing I was wondering about (and it has nothing to do with SLI): The version of Vista I purchased is for "system builders" and I know that I can't reinstall it if I get a whole new system. But will Vista consider various upgrades as a new system, and therefore disable itself. For example: if I, down the road, decide to change out my video cards and processor, will Vista shut down (thinking it's a different computer)?

The only reason I got this version of vista was because it was only $10 more than a new XP disc. I don't want to get stuck with a dead OS in a year or so, just because I wanted an upgrade.

And I won't be stuck with a dead computer, as long as I use linux (a real OS). I just wont be able to play City of Heroes (I've tried to use Cedega in linux to play COH, but I couldn't get it to work right).

Most likely yes, I've seen XP Pro want a reactivation with as little a enabling my onboard sound for testing purposes


As for game compatibility, your best bet is to dual-boot with XP Home/Pro 32-bit and then on another partition or HDD, to install Vista onto.

This way you can pick which OS is the default and which is the secondary for running games that have issues with Vista.

This is pretty much what I do as I play Lineage 2 a lot and that freaking GameGuard is teh suk :evil:

Will this mean that I have to buy a third party partition utility the get the two different versions of Windoze installed? I always installed Windoze before Linux bucause Linux has it's own bootloader (I prefer LILO over GRUB), and it has the windoze partitions as an option.

Also, can I have 2 HDD in raid zero as one drive (C:), and 2 other HDD in raid zero as another drive (D:)?

Nope, you just install Windows XP onto one drive or partition and get it all updated and running properly then go and install Vista.

During the setup process you will have a choice to setup Vista on another drive or partition. So really this is the only thing extra you need, a second HDD or a large single HDD that has been split into two partitions

Both Vista and XP have built-in Boot Managers that allow you to select the OS you want to load along with a menu option.