Family resemblance : meet the twin brothers

So let's have a look at the card lying before us :



Many people would recognise this card easily as being a 7900GT, however they would be mistaken. This card is a 7900GT which has been stripped down ever so slightly. nVidia uses the same core on the 7900GS (the G71), but has slimmed down the number of pipes in comparison with the 7900GT. The card features a very nice looking black PCB, which makes it look really classy. On top of that it has what I'll call a "sidebar" on the edge. It's visible for example through a side window in your case. This not only distinguishes the cards from other Manufacturers, but gives it an additional cool factor as well!

As the 7900GS is theoretically nothing more than a handicapped 7900GT, it's fairly natural that the two cards are going to becompared to one another. As you can see from the following pictures, the PCB's of the two cards are almost identical.


The 7900GT above the 7900GS

The 7900GS to the right of the 7900GT

Not only from the outside the resemblance is striking. Let's pop the hood !


Left to right (click to open) : XFX Core, MSI Core, MSI memory, XFX Memory

As you can see, the cores of the two cards resemble each other very much. The (quite early) sample of the MSI 7900GT does mention the "GT" on its core, the 7900GS does no such thing.
Taking a look at the memory shows us that both cards utilize the same speed of memory, but from a different brand. MSI has the samsung 1.4ns modules on board, whereas XFX goes for hynix modules with a speed of 1.4ns as well. 1.4ns memory equals a theoretical speed of about 715Mhz, but as we'll see later on these both of these modules run easily above their spec.

For those who wonder whether a 7900GS can be softmodded to a 7900GT, I'll have to disappoint you. From what I've heard the pipelines are laser-removed, and non recoverable. So those who really want the full 24 pipes of the GT and GTX will have to open up their wallets.

The following table gives a nice overview of nVidia's current product lineup :

model (name, socket)		cores		core/mem	pixel/vertex/ROP
GeForce 7100 GS	PCIe	1x	G72	350/300	4/3/2
GeForce 7300 GS	PCIe	1x	G72	550/400	4/3/2
GeForce 7300 GT	PCIe	1x	G73	350/333	8/4/4
GeForce 7300 LE	PCIe	1x	G72	450/350	4/3/2
GeForce 7600 GS	PCIe	1x	G73	400/400	12/5/8
GeForce 7600 GT	PCIe	1x	G73	560/700	12/5/8
GeForce 7800 GS	AGP 8x	1x	G70	375/600	16/6/8
GeForce 7800 GT	PCIe	1x	G70	400/500	20/7/16
GeForce 7800 GTX	PCIe	1x	G70	430/600	24/8/16
GeForce 7800 GTX 512MB	PCIe	1x	G70	550/850	24/8/16
GeForce 7800 Go	PCIe	1x	G70	400/530	24/8/16
GeForce 7900 GS	PCIe	1x	G71	450/660	20/7/16
GeForce 7900 GT	PCIe	1x	G71	450/660	24/8/16
GeForce 7900 GTO	PCIe	1x	G71	650/690	24/8/16
GeForce 7900 GTX	PCIe	1x	G71	650/800	24/8/16
GeForce 7900 GX2	PCIe	2x	G71	500/605	24/8/16
GeForce 7950 GT	PCIe	1x	G71	550/700	24/8/16
GeForce 7950 GX2	PCIe	2x	G71	500/600	24/8/16

In the table, we highlighted todays test candidate, the 7900GS.
As you can see, the difference between the GT and the GS is that the number of pipelines has been reduced. The core and memory speeds are actually the same on both the cards. In comparison with the 7900GT the GS is missing 4 pixel pipelines and 1 vertex pipeline, the number of raster pipes remains unchanged. These changes make the 7900GS quite logically the slower card of the two, clock for clock. How big the difference exactly is we'll see in the next pages.
The flip side of this stripped down 7900GT is of course that they sell it a lot cheaper. The 7900GS comes with an MSRP of $199 compared to $299 for the 7900 GT. nVidia was of course in bare need of a competitive card in this price range, as it left the market almost entirely for the X1900GT. The competitive price makes the 7900GS more interesting for a lot of people now, although the 7900 GT is potentially up to 20% faster in raw pixel processing power. The card we're looking at today however has an extra trick upon its sleeve : it comes factory overclocked ! Our test sample runs out of the box at the speed of 480mhz for the core (up from 450Mhz), and 700Mhz (1400Mhz DDR) for the memory (up from 660Mhz). XFX does sell this card a little over the $199 MSRP, but I can already assure you that the price difference is justified in this case !


The back of the card

Test setup

Time to have a look at our test system :

Core 2 Duo Test Setup
CPU	Intel E7400 "Merom" Core 2 Duo @ 2.86Ghz Cooled by Thermaltake Big Typhoon
Mainboard	Aopen i975-YDG
Memory	2x 512Mb OCZ PC2-6400 Fat Body kit @ 4-3-2-1
Other	MSI 7900GT @ 450/660 XFX 7900GS @ 450/660 XFX 7900GS @ 480/700 Nec DVD 16/48 Western Digital Raptor 74Gb SATA OCZ Powerstream 600W

This is what we call a "mobile on the desktop" setup, with a Core 2 Duo "Merom" CPU that was slightly overclocked from 2.13Ghz to 2.86Ghz. This cpu speed was maintained throughout the entire test session. It is a rather high end setup which should support the test of the graphics solutions really well, without forming a bottleneck in our tests.
As you can see, we're putting 3 different cards on the test bench: the first will be the standard 7900GS (simulated by an underclocked XFX), the second the standard XFX 7900GS "extreme edition", and the third the 7900GT.

Let's have a look how these three relate to one another ->