PCB Design and Cooling System
Nvidia’s ban on developing and utilizing unique PCB designs for senior models of the GeForce series does not cover GeForce 7900 GT/GS, GeForce 7950 GT as well as less advanced GeForce 7 models. However, ASUS decided to stick to the reference design with its EN7950GT and EN7900GS Top.
You can see it in the photographs that the graphics cards are both made by the reference design, the azure color of the PCB being the single difference. Each card is equipped with two DVI-I outputs and a universal 7-pin S-Video/YPbPr connector. Neither of them carries a VIVO chip. Thus, you can only tell the EN7950GT from the EN7900GS Top visually by the marking on the memory chips or by the stickers on the reverse side of the PCBs.
The ASUS EN7950GT carries 512MB of GDDR3 memory in eight HYB18H512321AF-14 chips from Infineon. These chips have a capacity of 512Mbit, 2.0V voltage and a rating frequency of 700 (1400) MHz. This is indeed the frequency the memory is clocked at by the card, providing a bandwidth of 44.8GB/s. Most of the GPU subunits are clocked at 550MHz and the vertex processors, at a 20MHz higher frequency. The frequencies are the same as those of the reference GeForce 7950 GT.
The ASUS EN7900GS Top uses Hynix HY5RS573225A FP-14 memory (256Mbit, 1.8V, 700 (1400) MHz). The chips are clocked at 720 (1440) MHz on the card, providing a bandwidth of 46GB/s instead of 44.8GB/s, yet this can hardly have a big effect on performance of the EN7900GS Top in games. It is the GPU frequency that ensures an increase in speed. It is 590MHz for the main GPU subunits and 610MHz for the vertex processors. This is far over the reference card’s 450/470MHz and may indeed provide the promised 20% performance boost. We’ll check this out soon.
The increased clock rates are the only point where the ASUS EN7900GS Top differs from the ordinary GeForce 7900 GS if you compare their specifications. They have the same amount of active GPU subunits: 20 pixel processors, 7 vertex processors, 20 TMUs, and 16 ROPs.
The EN7950GT and the EN7900GS Top are both equipped with the standard cooler we described in our reviews of Nvidia’s GeForce 7900 GT, 7900 GS and 7950 GT: a folded sheet of copper is glued to a small copper base. The cooler is equipped with a 45mm fan. The whole arrangement is covered with a plastic casing and secured on the PCB with four spring-loaded screws. Dark-gray thermal grease serves as a thermal interface. The memory chips are not cooled.
The reference cooler is popular due to the low heat dissipation of the G71 chip, but it may prove not that efficient when the G71 is clocked at 550MHz or higher. ASUS is confident the card won’t overheat, but we’d recommend you to make sure your system case is ventilated well before you try to install and use an EN7950GT and, especially, an EN7900GS Top.
We hadn’t expected much from the EN7950GT and EN7900GS Top as concerns overclocking, but the senior model did surprisingly well: we increased the GPU frequency from 550MHz to 660MHz and the card was perfectly stable (we even notched 675MHz at first, but had to roll back to 660MHz for the card would overheat and enter the throttling mode even while being cooled by an additional fan). The memory chips did well enough, too, speeding up from their default 700 (1400) MHz to 800 (1600) MHz. Thus, we reached the parameters of the GeForce 7900 GTX without “heavy” overclocking methods like volt-modding or liquid cooling.
Being already overclocked by the manufacturer, the EN7900GS Top performed modestly in that test, notching 620MHz and 820 (1640) MHz for the GPU and memory, respectively. The GPU frequency gain being very small, we decided not to benchmark the EN7900GS Top at the increased frequencies.
We want to remind you that the described graphics cards from ASUS are both equipped with the reference cooling system which is not too efficient. If you are going to overclock either of these cards, you should think about replacing the native cooler with something better. Otherwise the card may get damaged due to overheat.