XFX Overclocked GeForce 7950 GX2 (PV-T71U-ZDD9) Review

Introduction

GeForce 7950 GX2 is the latest high-end video card presented by NVIDIA and XFX has this model, “GeForce 7950 GX2 M570 1GB DDR3 XXX” (PV-T71U-ZDD9), which comes factory-overclocked. GeForce 7950 GX2 uses a very different design: it is actually two GeForce 7950 video cards stacked together. So it has two GPUs and a total of 1 GB of video memory (512 MB for each GPU). The good news is that it can be installed on any PCI Express motherboard – your motherboard doesn’t need to be SLI for you to install this beast. Let’s see how faster is this overclocked model against the regular GeForce 7950 GX2 and also against other products available on the market, especially Radeon X1900 XTX and GeForce 7900 GTX.

Each GPU found on GeForce 7950 GX2 normally runs at 500 MHz accessing its memory at 1.2 GHz (600 MHz DDR). This reviewed model from XFX runs at 570 MHz and accesses its memory at 1.55 GHz (775 MHz DDR). You see this factory-overclocked video card from XFX in Figure 1.

Figure 1: XFX Overclocked GeForce 7950 GX2 (PV-T71U-ZDD9).

The two GPUs are connected to the x16 PCI Express slot through a switch chip. According to NVIDIA, at this time each GPU is connected to this switch using eight PCI Express lanes, i.e., 8x performance, not 16x. Another thing to keep in mind is that each GPU is connected to its own 512 MB video memory using a 256-bit interface. Because of this GeForce 7950 GX2 is said to have 1 GB video memory accessed using a 512-bit interface. We prefer to list this video card as having 512 MB x 2 video memory and 256-bit x 2 memory interface, as this describes more accurately the architecture used by this video card.

This switch chip is 100% compatible with PCI Express specification, not requiring SLI-based motherboards. NVIDIA states that some motherboards may not be compatible with this chip and that a simple motherboard BIOS upgrade shall solve the issue. We reviewed this card using a DFI LAN Party 925X-T2 motherboard, which is based on Intel 925X chipset, and we had no problem at all, no BIOS upgrade was needed.

XFX currently has three GeForce 7950 GX2 models on their catalog:

PV-T71U-ZDL9: 500 MHz clock, 1.2 GHz memory clock, 512 MB 256-bit GDDR3 x 2. A.k.a. “XFX GeForce 7950 GX2 M500 1GB DDR3”, that’s XFX version for the standard GeForce 7950 GX2.
PV-T71U-ZDF9: 520 MHz clock, 1.3 GHz memory clock, 512 MB 256-bit GDDR3 x 2. A.k.a. “XFX GeForce 7950 GX2 M520 1GB DDR3 Extreme Edition”.
PV-T71U-ZDD9: 570 MHz clock, 1.55 GHz memory clock, 512 MB 256-bit GDDR3 x 2. A.k.a. “XFX GeForce 7950 GX2 M570 1GB DDR3 XXX”, that’s the model we are reviewing.

As you can see, XFX is now posting the clock rate on the VGA model name, helping users to identify overclocked models.

You can see in our tutorial “NVIDIA Chips Comparison Table” the difference between GeForce 7950 GX2 and the other chips from NVIDIA, while on our tutorial “ATI Chips Comparison Table” you can compare it to its competitors from ATI.

On Figures 2 and 3 you can see XFX GeForce 7950 GX2 M570 1GB DDR3 XXX (PV-T71U-ZDD9). In Figure 4, you can see a profile view of the reviewed card, where you can see its two stacked printed circuit boards.

Figure 2: XFX Overclocked GeForce 7950 GX2 (PV- T71U-ZDD9).