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PCB Design and Cooling System

The G73 having been originally optimized for low power consumption, it wasn’t a hard job for Nvidia’s engineers to make the PCB of the GeForce 7600 GT simple and small:

The GeForce 7600 GT is shorter than the GeForce 6800 GS which used the GeForce 7800 GT’s PCB. The dimensions of the XFX card are comparable to those of the GeForce 6600 GT, and this is no marvel considering the use of 0.09-micron low-k tech process. It’s just progress, you know.

The GeForce 7600 GT’s power circuitry is, however, somewhat more complex than the GeForce 6600 GT’s. It is based around two Intersil ISL6549CBZ controllers located on the reverse side of the PCB, one of which is responsible for the GPU and the other for the memory. Apart of them, there’s nothing interesting on this side of the PCB, except for the seat for a VIVO chip. This seat is sealed with a sticker with patent numbers on the XFX product. It seems that the installation of the VIVO chip is not required, but possible. Today, the option of capturing analog video signal is not demanded much, while the cost of the product is reduced a little by not putting the appropriate chip on the PCB.

It should be noted that unlike on the GeForce 6600 GT, there is no place for an additional power connector on the GeForce 7600 GT. That’s explicable: the more advanced GeForce 7900 GT card consumes less than 50W in 3D mode and could quite well be satisfied with the amount of power the PCI Express slot can provide. The G73 has even fewer functional subunits than the G71, so it’s logical that solutions on this GPU do not call for external power, even accounting for the additional inactive quad of pixel processors. We already know that the power consumption of the GeForce 7600 GT is about 35W in 3D mode, but the XFX GeForce 7600 GT XXX Edition works at higher GPU and memory frequencies and thus needs a little more power.

The G73’s memory interface is 128 bits wide, so four GDDR3 chips from Samsung (K4J52324QC, 16Mx32 organization) are used to provide 256 megabytes of graphics memory. With only four memory chips on board, the wiring of the PCB is made much simpler and, accordingly, cheaper. The BC14-suffixed chips have an access time of 1.4 nanoseconds and can work at frequencies up to 700 (1400) MHz. This is the standard memory frequency for the GeForce 7600 GT, but the memory of the XFX GeForce 7600 GT XXX Edition is pre-overclocked by the manufacturer to 800 (1600) MHz.

So, the peak memory bandwidth of this graphics card is 25.6GB/s as opposed to the standard GeForce 7600 GT’s 22.4GB/s, which is, however, still lower than the Radeon X1800 GTO’s 32GB/s. Note that the memory chip work at a higher frequency than they are rated for, so it is possible XFX had ensured its stability by increasing its voltage.

The G73 chip installed on our sample of the XFX GeForce 7600 GT XXX Edition is revision A2 and was manufactured at the beginning of 2006. The die area is small due to the low transistor count and the 0.09-micron tech process. The die is smaller than the NV42’s or NV43’s and looks quite a midget in comparison with ATI’s R520 employed in the Radeon X1800 GTO. There’s no protection of the core against physical damage, but that’s not a problem with the small and light cooler the GeForce 7600 GT is equipped with. The core frequency of the XFX GeForce 7600 GT XXX Edition is 590MHz which is 30MHz above that of the reference card.

Quite typically for a modern graphics card, the XFX GeForce 7600 GT XXX Edition has two DVI-I connectors and a universal video output. As opposed to the G71, the G73 chip has only one TMDS transmitter that is capable of working in dual-link mode, so only the lower DVI-I connector, closest to the PCI Express slot and the mainboard, can be used to connect an LCD monitor with support for 2560x1600 resolution. The mounting bracket of this card differs from the standard one in having a special tab with a barcode sticker. It is this tab that you see through the smaller window in the package.

The XFX GeForce 7600 GT XXX Edition carries an ordinary reference cooler, the same as you see on any other version of the GeForce 7600 GT. This cooler should be familiar to our readers from our GeForce 7900 GT review. It consists of a copper bar and a folded copper sheet which is glued to that bar. The whole thing is covered with an air-directing casing and is equipped with a small blower with a blades diameter of 45mm and a power draw of 2.16W (0.18A x 12V). This is a simple and not very efficient design, but it suffices for cooling the low-consumption G73 chip even on the overclocked GeForce 7600 GT. The cooler is firmly secured on the PCB with four spring-loaded screws, so there’s low probability that it can crack the GPU die. The cooler’s base contacts with the GPU core through a layer of thick dark-gray thermal paste. The cooler does not touch the memory chips.

The single difference of the cooler installed on the XFX GeForce 7600 GT XXX Edition from the reference one is that it carries a sticker with the XFX logotype on the casing. The blower has a two-contact connection to the card, but there’s a seat for a 4-pin connector nearby. The same seat can be seen on the GeForce 7900 GT, so we suspect it had been planned to mount coolers with a different, perhaps more efficient, design on the GeForce 7900 GT and GeForce 7600 GT – at least coolers with different fans. As you know, the GeForce 7900 GT lacks any fan speed management system, and this affects its noise parameters negatively – the card is loud in any mode. We’ll tell you later on in this review if the same is true for the GeForce 7600 GT.

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