AMD HD 6970 and HD 6950 Reviewccokeman - December 14, 2010
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From a packaging perspective, the HD 6970 and HD 6950 from XFX are almost identical to the HD 6870 and HD 6850 I looked at back in October. The front panels have a unique industrial design. To the left of the product name is the XFX logo and "Play Hard" slogan.To the right is the Radeon graphics logo. The basic specifications of the card are listed below and include 2GB of GDDR5 memory. This is an increase in the frame buffer size from the Cypress and Barts core equipped cards that preceeded these "Cayman" equipped graphics cards.There is also a small logo the lets you know that in the event that something does go wrong, XFX will stand behind these HD 69xx cards with their 5 Star support. The back panels rattle off the key features of these cards that include AMD Advanced Parallel Processing Technology (APP), HDMI 1.4a support, AMD PowerPlay technology, Eyefinity , Windows 7 support, DisplayPort 1.2 output, 2GB of GDDR5 and more.
Inside the outer sleeve is the box that contains the graphics cards and the accessory bundle. The box is black in color and features the XFX logo, slogan and the web address. Inside you will find the boxes are split into two areas, one that holds the documentation and accessories while underneath you have the video card in a formed cardboard tray.
The accessory bundle is a bit slim but contains the driver disk, warranty literature, quick install guide, driver install guide, a crossfire bridge connection and a staple from XFX being the door tag that lets people know your're in the midst of a frag session. Flip the door tag over and you have all the information needed so that you can register your card so that support (if you ever need it) can be tailored to your individual device.
The HD 6900 series cards from XFX are in essence reference design video cards that mirror the specifications and feature set of this design from AMD. The front of each card features the industrial looking graphic used on the packaging. These reference design cards are two slot solutions much like just about every high performance video card that has come out in the past few years with few exceptions. The back side of each card is covered with a plate that serves to keep the PCB from flexing as well as a way to keep the main heat sink in place. The HD 6900 series are built using a 40nm process and are built on a new VLIW4 graphics architecture with dual graphics engines in a single GPU core that show a 10% increase in performance per mm2. The HD 6970 comes equipped with 24 SIMD engines, 1536 streaming processors, 96 texture units, 32 ROPs and 2GB of GDDR5 memory running through a 265bit bus that delivers 2.75 TFLOPS of compute performance. The HD 6950 uses the same technologies but comes with a lesser amount of hardware on board at 22 SIMD engines, 1408 streaming multiprocessors, 88 texture units, 32 ROPs and the same 2GB of GDDR5 memory running through a 256bit bus delivering slightly less performance at 2.25 TFLOPS. We can see that AMD has continued with the use of the blower fan style cooling that hopefully has been revamped much the way NVIDIA did recently on their GTX 5XX series cards.
By following the reference design you get the reference connectivity options. The I/O panel on both the HD 6970 and HD 6950 show that you get a pair of DVI ports (one of which is single link while the other is Dual Link capable), a pair of mini DisplayPort 1.2 ports and a single HDMI 1.4a port. With the display port 1.2 options you have the ability to run a total of six monitors off of a single card using Multi Stream Transport where three monitors can be fed from a single DisplayPort 1.2 capable port. You will however, have to use monitors that support daisy chaining or use an MST hub. This gives you the ability to run a six monitor Eyefinity setup without having to purchase a specialty video card. The exhaust vent for these cards deviates from the reference design and lets you know what brand of video card you are running. Its a specialty feature that sets the XFX cards apart from the pure reference design. Airflow should not be impacted by this and was shown to not be an issue with the HD 6800 series cards we looked at from XFX. However with the amount of air peing pushed by the blower fan assembly, the exhaust is on the small side for a high-end graphics card. The back end of the card is featureless and contains the red accent ribbing used on the 6000 series reference cards.
These two cards are able to be used in a CrossfireX multiple GPU configuration with up to four cards. Instead of the single bridge connection used on the HD 6800 series cards, the 6900's are a step up to the enthusiast hardware level and as such, AMD provided the ability to use more than a two card configuration for additional gaming performance. On the HD 6970 you will notice a small (well, not so small really) switch on the top of the card right next to the Crossfire bridge connections. This switch is called the Dual BIOS toggle switch and is used to provide a second unprotected user configurable BIOS in addition to the protected factory default BIOS. This way, if you have a bad flash, at least you can revert back to the stock BIOS to get yourself out of trouble. A pretty neat feature that the more experienced users can take advantage of to modify the secondary BIOS for use when benchmarking or gaming where higher clock speeds are needed for added performance. The HD 6950 includes this feature in its list of attributes. The power connections for the HD 6970 are an eight pin + six pin configuration while the HD 6950 uses a six pin + six pin setup due to the difference in TDP. The HD 6970 has a 250 watt TDP while the HD 6950 is rated at 200 watts. A 550 watt power supply is recommended.
When you pull both the HD 6970 and HD 6950 apart they look identical in every way. The cover is held on with clips that index onto the aluminum heat sink body that covers the voltage regulation circuits and the 2GB of GDDR5 memory. Once the cover is off you can see the large Vapor Chamber heatsink that is used to cool the Cayman based cores on the cards. This heat sink sits above the aluminum heat sink body for the card and is in fact glued to this body.
When you pull the heat sinks from the card you can see the large vapor chamber that is covered with a full length fin array. Air is pushed through this array via the blower style fan that is used by AMD. One thing that looks to be missing is a way to direct all of the airflow through the fin array (instead of allowing air to move around it) by using a small gasket like that used recently on the GTX 570. The direct competitor of the HD 6970.
The core used on the HD 6970 is the Cayman XT while the HD 6950 gets the Cayman Pro. This is the main difference between the two cards and really reflects how much hardware is enabled inside of each core. The Cayman XT used on the HD 6970 is built on a 40nm process, is 389mm2 in size, has 2.64 billion transistors, has a total of 24 SIMD/1536 Stream processors, 96 texture units, 32 ROPs with clock speeds of 880MHz on the core and 1375MHz on the GDDR5 memory. With these specifications it delivers 2.75TFLOPS of compute performance. The Cayman Pro is built on the same 40nm process and has the same 2.64 billion transistors and 389mm2 size but has fewer SIMD engines at 22, 1408 streaming multiprocessors, 88 texture units, 32 ROPs, with clock speeds of 800MHz on the core and 1250MHz on the GDDR5 memory for a total of 2.25 TFLOPS of compute performance. The 2GB of GDDR5 memory used on the HD 6970 is from Hynix and is part number H5GQ2H24MFR ROC and is rated for operation at 1500MHz while the Hynix the HD 6950 uses a lower rated H5GQ2H24MFR T2C. The memory on both cards runs through a 256 bit bus to deliver memory bandwidth numbers of 176 and 160 Gbps respectively.
The Cayman series GPUs are built on a new VLIW4 architecture that uses dual graphics engines that are said to be 10% more efficient per mm2 than the last gen VLIW5 core. This design includes a second 8th generation tessellation unit to improve tessellation performance by 3x over the HD 5870 as well as improvements in the Compute structure of the core. These slides from AMD illustrate the improvements.
Now that we know what we are looking at in this generation of GPU's from AMD and XFX, it' time to see just how well they perform.