Sapphire Radeon HD 7950 3GB Vapor-X ReviewWaco - September 18, 2012
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If you read over OCC's review of the Sapphire HD 7970 Vapor-X GHz Edition, you might do a double-take on these pictures. The Sapphire HD 7950 3GB Vapor-X looks identical to the naked eye, with the exception of the model number stickers on the backside of the card. Just like the 7970 Vapor-X card, the trademark Sapphire Vapor-X cooler keeps the card cool and quiet at the same time with dual 92mm fans. The Sapphire blue PCB is identical to that on the Sapphire HD 7970 Vapor-X GHz Edition as well - right down to the 8-phase power featuring "Black Diamond" chokes and DirectFET technology to deliver power to the GPU core smoothly and efficiently. Unlike many older cards, this HD 7950 does not include a backplate, as there are no core components on the backside of the PCB that require cooling. On the side of the cooler, you can see the Sapphire logo that lights up in brilliant white whenever the card is powered on. On the other side of the heatsink shroud, you can see the two pairs of 6 mm and 8 mm heatpipes sneaking out from the vapor chamber. This card is intended to be run in a PCIe 3.0 x16 slot, but is also backwards compatible with the PCIe 2.0 specification.
Unlike many other cards in AMD's top-end 7900 series, the Sapphire HD 7950 does not have a pair of mini-DisplayPort ports. Instead, it replaces them with a single full-size DisplayPort port. Along with the larger DisplayPort port, there is an HDMI port, a single link DVI port, and a dual-link DVI port. If you're planning on using Eyefinity with this card, you'll need, at the very least, an active DisplayPort to DVI or DisplayPort to HDMI adapter to get up and running. The backplate does have a small port for air to exhaust out of the heatsink and behind your case, but the majority of the heat load from this card will be dumped into the interior of your case. Most cases built in the past few years have been designed with the thermal load of a graphics card in mind, but if you have an older case, it is possible that you'll see higher CPU temperatures from this design versus the fully-exhausted heatsink on the reference card. Other than the single connection for the dual 92 mm fans, the back side of the card is essentially bare.
This Sapphire HD 7950 3GB VaporX supports configurations up to four-way CrossfireX. Here is where the vaunted Vapor-X cooler is a disadvantage though: it requires more than 2 slots of space on your motherboard. Unless you have a very odd board with enough room for three or four 2.5 slot cards, you won't be running anything other than standard two-card Crossfire. If you do manage to find a board that fits three or four of these cards (or you outfit them with custom full-cover water blocks), there are two Crossfire fingers to allow interconnection between the various GPUs and lessen the crosstalk load on your PCIe slots. Right next to those Crossfire fingers is the inconspicuous little Sapphire EZ OC button. Pressing this boosts the clocks from 850 MHz on the core right up to 950 MHz without any effort at all. I can't imagine why you'd ever turn this off...but just in case, Sapphire has made the button light up in bright Sapphire blue to give you a quick visual indicator that the button is enabled for maximum performance. Moving to the other end of the card, you can see the two PCIe power connections; one 8-pin (150 watts) and one 6-pin (75 watts). Combined with the 150 watts available from the PCIe x16 slot, this card can pull up to 375 watts before violating the PCIe specification.
Removing the Vapor-X cooler is a simple task; four screws and a bit of force pull it free from the PCB. Below, you can see the bare PCB, video memory, and power circuitry on the right. Sapphire has upped the ante and provided this card with full 8-phase power for both higher efficiency and cooler temperatures. A single CHiL CHL8228G voltage controller is used to control how much voltage the 8-phase circuitry sends to the GPU core and memory.
Like Sapphire's past cards, the Vapor-X cooler is no slouch. With a large vapor chamber directly cooling the core and four heatpipes (two 6 mm and two 8 mm) pulling heat from the vapor chamber out to the aluminum cooling fins, this heatsink is definitely built to cool! The base that contacts the core is stamped smoothly and lapped for optimal contact and heat dissipation. Around the vapor chamber itself is a large aluminum baseplate that contacts the GDDR5 memory modules through twelve thermal pads. Along with the large main heatsink is a small extruded aluminum heatsink that covers the 8-phase power circuitry and is cooled by the downflow from the rightmost fan on the cooler.
Each of the fans used on the Sapphire HD 7950 3GB Vapor-X are identical. They both utilize a sealed bearing design to extend the life of the fans long past when standard fans would have failed from dust. Both are 92 mm in size and controlled via a PWM circuit on the card for smooth and quiet ramping of fan speeds from idle to load. Both can pull up to .55 amps at 12 volts (6.6 watts each), so while they can pull a fair amount of power, they won't blow the power budget even if you leave them at full speed 24/7. These fans were near silent in testing at stock speeds and only became audible when cranked to 100% for the overclocking section of testing. Even when pushed all the way to 100%, they were nowhere near as loud as a reference card ramped up to full speed (the blower-style cooler of the reference cards is notoriously loud).
Behold; the Tahiti Pro core. Boasting 1792 unified shaders (or Stream Processors if you want to call them that), 112 texture units, and 32 ROPs, this core is only slightly cut down from the full 28 nm Tahiti XT core (at 2048:128:32 respectively). With 4.31 billion transistors, this is no small core, even with the advanced 28nm process. With the EZ OC button engaged, the core runs at 950 MHz. The 12 GDDR5 dies are similar to those on the Sapphire HD 7970 Vapor-X GHz Edition, but are a slightly different model rated at 1250 MHz (Hynix part number H5GQ2H24MFR-T2C). Considering that I managed to get the memory stable at 1450 MHz, the realization that it was only rated at 1250 MHz revealed why overclocking it was so finicky...I was far beyond the rated speeds for the memory. The memory is connected to the GPU core via the same 384-bit bus that is employed on the full-fledged HD 7970 solution.
Now that you've seen the guts of this Sapphire HD 7950 3GB Vapor-X, move on to see how the awesome cooling solution and tweaked clock speeds perform in the OCC test suite!