X-bit labs

Affordable Multi-GPU: Two GeForce 9600 GT in SLI (page 3)

Category: Video

by Alexey Stepin

[ 04/19/2008 | 01:41 PM ]

PCB Design, Specs and Cooler

Nvidia’s reference design differs considerably from what Gainward used in its Bliss 9600 GT 512MB GS we reviewed earlier.

The power circuit is simpler: the GPU voltage regulator has two phases as opposed to three on the Gainward card. A dual-phase ADP3208A PWM-controller from Analog Devices is responsible for GPU power supply; we haven’t seen this chip before. Interestingly, the manufacturer’s website says that shipments of this chip were discontinued in 2008. As the reserves of such chips are exhausted, other power controllers may be installed on GeForce 9600 GT. The card receives external power through a standard 6-pin PCI Express 1.0 slot. The GeForce 9600 GT consuming about 60W, the card might do even with no external power at all, but the developer didn’t want to put all the load on the PCI Express slot.

The PCB carries eight GDDR 3 memory chips (K4J52324QE-BJ1A). The chips have a capacity of 512Mb (16Mb x 32), a voltage of 1.9V and a rated frequency of 1000 (2000) MHz. The Gainward Bliss 9600 GT 512MB GS comes with this memory, too. The card’s memory frequency is standard at 900 (1800) MHz. Accessed across a 256-bit memory bus, this ensures a bandwidth of 57.6GB/s. As we already know, the GeForce 9600 GT doesn’t suffer from insufficient memory bandwidth. The card has a total of 512 megabytes of memory, which is a standard capacity even for inexpensive mainstream solutions.

The GPU is revision A1. The card’s GPU frequencies are standard, too: 650MHz for the main domain and 1625MHz for the shader domain. The GPU configuration is standard with 64 universal scalar ALUs, 16 (32) TMUs, and 16 ROPs. The texture processors have the same architecture as in all latest solutions from Nvidia, i.e. with two filter units per each two address units. Theoretically, it means 32 TMUs, but from a practical point of view the GPU has rather 16 TMUs as there is no talking about “free” tri-linear and anisotropic filtering with this architecture. Practice suggests that the TMUs and ROPs are not a bottleneck in the G94 design, though. There is no protective frame on the GPU package, but that’s not a problem as the cooling system is small and light.

As opposed to the Gainward Bliss 9600 GT 512MB GS, the Gigabyte card has standard interfaces: two dual-link DVI ports and a universal connector for analog video output. Although the G94 incorporates an integrated DisplayPort controller, the card doesn’t allow for the installation of an appropriate connector. Besides the power PCI Express 1.0 connector, the PCB carries a standard MIO plug for SLI connection and a 2-pin S/PDIF plug for connection to the sound card’s digital output to enable the audio-over-HDMI feature.
The Gigabyte GV-NX96T512H-B comes with the reference cooler we are familiar with by the GeForce 8800 GT 256MB. It has a copper sole contacting with the graphics core and a heatsink considering of thin aluminum plates. Flat heat pipes in the cooler’s base help distribute the heat more uniformly. The cooler has a rather large fan. The heatsink being placed at an angle, the hot air is exhausted sideways, towards the side panel of the system case. The cooler is secured firmly with 12 spring-loaded screws to prevent any misalignment that might damage the GPU.

This cooler is not very efficient and its first version didn’t always cope with the job on the GeForce 8800 GT 512MB. The GeForce 9600 GT consumes less power and generates less heat, so the compact single-slot cooler is quite okay for it.