ATI Radeon HD 2900 XT: Calling a Spade a Spade
by Derek Wilson on May 14, 2007 12:04 PM EST- Posted in
- GPUs
Memory and Data Movement
Internal cache bandwidth on the R600 is 180GB/sec, while the internal memory bus, a second generation Ring Bus that builds on the X1k series idea, is able to deliver 100GB/sec of throughput in either read or write capacity. Memory offers nearly 110GB/sec, and AMD has stated that the internal bus is well matched to this due to the fact that some external bandwidth is wasted on overhead. The bottom line here is that a whole of data can move very quickly into and out of this hardware.
As we mentioned, R600 sees a reincarnation of the Ring Bus which can now handle both read and write data (X1k could only handle reads on the Ring Bus while writes were run through a crossbar). An independent DMA controller manages a bus comprised of multiple ring stops. There is one ring stop per pair of memory channels, and each ring stop is connected to two others via a 256 bit wide connection. The ring bus is 1024 wires total and can move read and write data in either direction to follow the shortest path around the ring to or from the memory client or memory.
The Ring Bus allows the PCI Express bus to be treated like just another memory device by the rest of the hardware. The DMA hardware is able to manage all the traffic to and from onboard and system memory in the same manner, and the memory clients on the GPU don't need to know what device they're talking to. The Ring Bus services 84 read clients and 70 write clients.
The external memory interface is 512-bit, doubling the X1k maximum of 256-bit and surpassing G80's 384-bit memory bus. Memory speeds are lower than on previous generation high end AMD hardware, but total bandwidth is higher. The net result is that AMD only slightly edges out G80 for memory bandwidth.
In implementing the 512-bit memory interface, AMD didn't want to add any more I/O pads to its package. They accomplished this by making use of a stacked I/O pad design. Unfortunately, details were vague on the implementation and methods used to keep clock speed high in spite of the proximity of other high frequency I/O.
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Roy2001 - Tuesday, May 15, 2007 - link
The reason is, you have to pay extra $ for a power supply. No, most probably your old PSU won't have enough milk for this baby. I will stick with nVidia in future. My 2 cents.Chaser - Tuesday, May 15, 2007 - link
Such a revealing tech article. Thanks for other sources Tom.
archcommus - Tuesday, May 15, 2007 - link
$300 is the exact price point I shoot for when buying a video card, so that pretty much eliminates AMD right off the bat for me right now. I want to spend more than $200 but $400 is too much. I'm sure they'll fill this void eventually, and how that card will stack up against an 8800 GTS 320 MB is what I'm interested in.H4n53n - Tuesday, May 15, 2007 - link
Interesting enough in some other websites it wins from 8800 gtx in most games,especially the newer ones and comparing the price i would say it's a good deal?I think it's just driver problems,ati has been known for not having a very good driver compared to nvidia but when they fixed it then it'll windragonsqrrl - Thursday, August 25, 2011 - link
lol...fail. In retrospect it's really easy to pick out the EPIC ATI fanboys now.Affectionate-Bed-980 - Tuesday, May 15, 2007 - link
I skimmed this article because I have a final. ATI can't hold a candle to NV at the moment it seems. Now while the 2900XT might have good value, I am correct in saying that ATI has lost the performance crown by a buttload (not even like X1800 vs 7800) but like they're totally slaughtered right?Now I won't go and comment about how the 2900 stacks up against competition in the same price range, but it seems that GTSes can be acquired for cheap.
Did ATI flop big here?
vailr - Monday, May 14, 2007 - link
I'd rather use a mid-range older card that "only" uses ~100 Watts (or less) than pay ~$400 for a card that requires 300 Watts to run. Doesn't AMD care about "Global Warming"?Al Gore would be amazed, alarmed, and astounded !!
Deusfaux - Monday, May 14, 2007 - link
No they dont and that's why the 2600 and 2400 don't existochentay4 - Monday, May 14, 2007 - link
Let me start with this: i always had a nvidia card. ALWAYS.Faster is NOT ALWAYS better. For the most part this is true, for me, it was. One year ago I boght a MSI7600GT. Seemed the best bang for the buck. Since I bought it, I had problems with TVout detection, TVout wrong aspect ratios, broken LCD scaling, lot of game problems, inexistent support (nv forum is a joke) and UNIFIED DRIVER ARQUITECTURE. What a terrible lie! The latest official drivers is 6 months ago!!!
Im really demanding, but i payed enough to demand a 100% working product. Now ATi latest offering has: AVIVO, FULL VIDEO ACC, MONTHLY DRIVER UPDATES, ALL BUGS I NOTICED WITH NVIDIA CARD FIXED, HDMI AND PRICE. I prefer that than a simple product, specially for the money they cost!
I will never buy a nvidia card again. I'm definitely looking forward ATis offering (after the joke that is/was 8600GT/GTS).
Enough rant.
Am I wrong?
Roy2001 - Tuesday, May 15, 2007 - link
Yeah, you are wrong. Spend $400 on a 2900XT and then $150 on a PSU.