PCB Design and Specifications
The EVGA GeForce GTX 275 CO-OP PhysX Edition is almost the same in face view as the single-card GeForce GTX 295 we described in an older review, but there are a few differences at the back:
However, you can still see that the PCB design of the GeForce GTX 275 CO-OP PhysX is largely copied from the reference PCB of the GeForce GTX 295. This practical approach must have saved EVGA some money on developing a completely new PCB. We didn’t have any problems dismantling the cooling system except that we had to unfasten a lot of screws. With the cooler removed, it became clear that the EVGA card and the single-card version of GeForce GTX 295 do differ although EVGA’s engineers had tried to utilize as much of the existing design as possible.
It is only in the front part of the card, where the place of a G200b is occupied by a G92b chip that serves as a PhysX/GPGPU accelerator, that a completely new wiring design is used. The power subsystem is almost the same as on the GeForce GTX 295: each processor is powered by an independent 3-phase regulator based on Renesas R2J20651 packs managed by an ADP3193A controller from Analog Devices.
The memory power subsystem has changed somewhat: a Renesas R2J20651 with an unknown chip marked as N12 VGF932 are responsible for the memory belonging to the main GPU.
The memory chips related to the G92b coprocessor are powered by a regulator based on ordinary MOSFETs and managed by an uP6161 chip from uPI Semiconductor.
The rest of the card’s components are powered by regulators based on uP6161 and APW7142 chips.
Like the GeForce GTX 295, the EVGA GeForce GTX 275 CO-OP PhysX has two power connectors, one of which is of the 8-pin variety. We guess two 6-pin connectors would be quite enough, however, because the G92b chip has a much lower power draw than the main G200b. The card won’t start up if you connect a 6-pin plug into its 8-pin connector, reporting a power problem with the LED indicator on its mounting plate, unless you bypass this protection.
There is only one NVIO2 chip here because the G92b contains all the necessary logic inside. Moreover, it does not need this video output logic since its purpose is limited to PhysX and CUDA applications. An nForce 200 chip is responsible for switching the PCI Express bus. It is marked differently than on the GeForce GTX 295: “NF200-SLI-A3” as opposed to “NF200-P-SLI-A3”.
The main core, which works as a graphics processor, is marked as G200-105-B3. The second number in the marking means that this model is manufactured out of the same chips as the ordinary versions of GeForce GTX 275 whereas the GeForce GTX 295 uses chips marked as G200-400/401-B3. Our sample was manufactured on the 41st week of 2009 and is clocked at 633/1296MHz. Thus, its shader domain frequency is lowered for some reason (it is 1404MHz with the ordinary GeForce GTX 275). This means that the GeForce GTX 275 CO-OP PhysX is going to be somewhat slower in games despite its physics processor.
The GPU’s memory bank has the same specs as on the GeForce GTX 275: 896 MB, 448 bits, 1134 (2268) MHz. The peak memory bandwidth is 127 GBps. The EVGA GeForce GTX 275 CO-OP PhysX uses GDDR3 chips from Hynix (H5RS5223CFR-N2C, 512 Mb) with a rated frequency of 1200 (2400) MHz, so there is some overclocking headroom left.
The dedicated PPU installed on this card is an ordinary G92b chip manufactured on 55nm tech process. Our sample was made on the 37th week of 2009 and is marked as G92-421-B1. It is clocked at the same frequencies as the core of the ordinary GeForce GTS 250, i.e. 738/1836 MHz. If the engineers had any apprehensions regarding the heat dissipation of the card, they should have reduced the clock rates of the coprocessor rather than of the main GPU, which is responsible for 3D rendering. This would help avoid the performance hit in games. We don’t know why the engineers preferred to slow down the main GPU but we will measure the performance hit in our tests.
Interestingly, one RBE section is disabled in the coprocessor due to the reduced amount of memory: 384 MB instead of 512 MB. The memory bus has become narrower. This memory bank consists of Hynix H5RS5223CFR-N2C chips, too. With a 192-bit bus and a clock rate of 1100 (2200) MHz, the memory bandwidth is 52.8GBps. EVGA’s engineers must have thought this enough for the coprocessor that does not have to do any 3D rendering and is limited to PhysX computations. Considering that the inexpensive GeForce GT 220 is also promoted as a physics effects accelerator, the GeForce GTX 275 CO-OP PhysX seems to have more than enough resources to accelerate physics.
As for interfaces, the card is equipped with two dual-link DVI-I ports (which can transfer S/PDIF audio over HDMI) and two MIO connectors for SLI technology. Thus, you can add two ordinary GeForce GTX 275 cards to this one to build a 3-way SLI subsystem in which three G200b processors are used for 3D rendering and a dedicated G92b processor with its own memory is responsible for PhysX computations, without utilizing any resources of the main GPUs. This looks appealing in theory, but practically, there are faster solutions available for demanding gamers, for example the Radeon HD 5970. Besides, our EVGA GeForce GTX 275 CO-OP PhysX refused to work together with a GeForce GTX 275 if installed into the mainboard’s top PCIe x16 slot. It is only when we installed it into the bottom slot (and the ordinary GeForce GTX 275 into the top one) that we could make this SLI configuration work.
The cooling system of the EVGA GeForce GTX 275 CO-OP PhysX is almost a copy of the one installed on the single-card GeForce GTX 295 and consists of two individual heatsinks each of which cools its own core.
This cooling system is usually quiet and effective. Its only drawback is that the hot air is not exhausted out of the computer case but stays inside. Here, this drawback is aggravated by the fact that the main G200b core, being much hotter than the simpler G92b chip, is located at the back of the card. That is, it is going to heat up the air inside the computer. Why didn’t the engineers put the G200b at the front to ensure better cooling for it? We don’t have an answer. Well, the EVGA GeForce GTX 275 CO-OP PhysX is indeed an odd and original solution and we know no other product similar to it. Now we just need to check out the practical tests. But before that, let’s take a closer look at its competitor – XFX Radeon HD 5850 Black Edition.