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PCB Design, Specifications, Cooling System

The described product from MSI employs the reference PCB design but only some of these cards seem to be bought read-made from Nvidia. NX8800GT series cards with the T2D512E index, i.e. equipped with 512 megabytes of graphics memory, come in two versions, V801 and V117, which differ at least in the color of the PCB. The former uses a classic green solder mask, and the latter, a red one, the corporate color of MSI. Our sample is V801 and we can’t tell you if it differs from V117 in anything else since we don’t have the latter. Cards from the same series but with the T2D256E index, i.e. with 256MB of memory, are coming to market in the V117 version only.

 

As you can see, the MSI NX8800GT-T2D512E-OC in its V801 version doesn’t differ in anything from Nvidia’s reference card except for the stickers on the cooler and fan. The picture on the cooler’s casing shows the same girl as on the box, and the sticker on the fan displays the MSI logo. The whole card is covered by the cooler casing, except for the PCI Express connector, and you can’t learn anything about the design of the card without removing it. As we had learned with the Leadtek WinFast PX8800 GT Extreme, it is not so easy to take it off. The plastic-like casing is actually made from metal and is not only secured with seven locks but also glued to the heatsink to prevent rattling. So, we had to dismantle the whole cooler (you can see the pictures of the same cooler in our previous article called From Extreme to Mainstream: Nvidia GeForce 8800 GT from Leadtek).

The card uses a three-phase power circuit governed by a Primarion PX3544 PWM-controller, and there are seats for elements of a fourth phase on the PCB. This must be a reserve for future cards that will be based on a fully unlocked G92 with 128 active shader processors. A simpler chip, Intersil ISL6549CBZ, is responsible for the memory chips. The card has one external power connector (a traditional, 6-pin, one) that is more than enough to satisfy the modest appetite of the G92. A piezoelectric speaker to the left of it emits a warning sound in case of problems with power supply.

The memory chips are placed in a semicircle around the GPU. The card carries 8 GDDR3 chips (Qimonda HYB18H512321BF-10, 512Mb capacity, 16Mbx32) in FBGA-136 packaging for a total of 512MB of graphics memory accessed across a 256-bit bus. The rated frequency of such chips is 1000 (2000) MHz but they are clocked at 950 (1900) MHz, which is 50MHz higher than the memory frequency of the reference GeForce 8800 GT card. This ensures a memory bandwidth growth from 57.6GB/s to 60.8GB/s, which is still below the GeForce 8800 GTS’ 64GB/s. This factory overclocking can’t provide a considerable performance boost, yet it leaves some elbowroom for your own experiments with the clock rates.

The GPU has open-die packaging. The frame should be quite enough to protect the die since the G92 has a smaller area than the G80.

This sample of the revision A2 G92 core was manufactured at the 40th week of 2007, in early October. The GPU has a standard configuration with 112 unified ALUs, 28 texture modules with two address units per each two filter units, and four rasterization units equivalent to 16 ROPs. Nvidia claims the core to have 56 texture-mapping units but the texture processors are actually equivalent to 28 TMUs (such as in the G80 core) due to the lower performance at tri-linear and/or anisotropic filtering.

The main domain frequency is increased by MSI from 600 to 660MHz. The shader domain frequency is lifted up from 1500 to 1650MHz. That’s somewhat lower than the frequencies of the Leadtek WinFast PX8800 GT Extreme (680/1700MHz), yet should bring about some benefits in games.

The MSI NX8800GT-T2D512E-OC offers a standard selection of connectors: two dual-link DVI-I ports with support of display resolutions up to 2560x1600, a universal 7-pin port for analog video output (Composite, S-Video, YPbPr), and a MIO connector for SLI configurations. The DVI ports are protected against dust with yellow plastic caps.

Notwithstanding the increased clock rates, the manufacturer limited himself to the reference cooler. We discussed it in our Nvidia GeForce 8800 GT review and will give you just a brief description here.

The new cooler developed by Nvidia for the GeForce 8800 GT has a single-slot form-factor. The cooler’s copper sole has immediate contact with the GPU die and transfers the heat to the heatsink consisting of thin aluminum plates by means of three flat heat pipes. The whole thing is installed on an aluminum foundation that has juts for contact with the memory chips and power circuit elements. Fabric pads soaked in white thermal grease are used there to ensure a proper thermal contact. Dark-gray thick thermal grease is used as a thermal interface between the GPU and the copper sole of the cooler. The grease covers almost the entire base of the cooler for some reason, although the G92 with its small die area doesn’t need that much. The cooler is secured on the card by means of 12 spring-loaded screws.

The cooler is equipped with a small but powerful blower with a 4-pin connection. Most of the time this fan has a reduced speed, but it is loud at its max speed when the system is started up. The heatsink is placed at an angle to the card’s longer side, so the hot air is exhausted towards the side panel of the system case, away from the card, and towards the DVI connectors. We don’t think it’s the best solution possible – Nvidia’s earlier coolers had a better design. For example, the fan of GeForce 6800/7800 cards was located near the interface connectors and exhausted the hot air at the card’s back, cooling the power circuit elements along the way.

The reference cooler does its job well enough notwithstanding the increased clock rates of the MSI NX8800GT-T2D512E-OC, but if you are seriously into overclocking or want to enjoy an absolute silence, you will have to replace it.

 
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