ATI Radeon HD 2900 XT: Calling a Spade a Spade
by Derek Wilson on May 14, 2007 12:04 PM EST- Posted in
- GPUs
Finally: A Design House Talks Cache Size
We're quite used to talking about cache sizes on Intel and AMD CPUs, but graphics hardware has been another story. We've been asking for quite some time, while other sites have taken to writing shader code to come up with educated guesses about how much data fits on die. Today we are very happy to bring you everything you could ever want to know about R600 caches.
The four texture units are connected to memory through two levels of cache. Unfiltered texture requests go through the Vertex Cache (which is unfiltered) and filtered requests make use of the L1 Texture Cache. Each of these caches is 32kB read only. All texture units share these caches.
Both the L1 Texture Cache and the Vertex Cache are connected to an L2 cache that is 256kB. This is the largest cache on the chip, and will certainly handle quite a bit of data movement with the possibility of 8k x 8k texture sizes moving forward.
As for the shader hardware, the cache connected to the SIMD units is an 8 kB read / write cache. This cache is used to virtualize register space if necessary, export data to the stream out buffer (which can be done from any type of thread and can bypass the need to send data to the render back ends). This cache is also used to accelerate things like render to vertex buffer.
Most of R600's write caches are write-back caches, although we weren't given any specifics on which write caches are not write-back. The impression is that any unit that needs to write out over the memory bus is connected through a write cache that enables write combining to maximize bus utilization, write latency hiding, and short term reuse. We assume that the shader cache (what AMD calls the Memory Read/Write Cache) is also write-back.
The only thing we are really missing regarding caches is the information for Z/stencil cache and color cache connected off of the render back ends.
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dragonsqrrl - Thursday, August 25, 2011 - link
You forgot c).-if you're an ATI fanboy
vijay333 - Monday, May 14, 2007 - link
http://www.randomhouse.com/wotd/index.pperl?date=1...">http://www.randomhouse.com/wotd/index.pperl?date=1..."the expression to call a spade a spade is thousands of years old and etymologically has nothing whatsoever to do with any racial sentiment."
strikeback03 - Wednesday, May 16, 2007 - link
What about in Euchre, where a spade can be a club (and vice versa)?johnsonx - Monday, May 14, 2007 - link
Just wait until AT refers to AMD's marketing budget as 'niggardly'...bldckstark - Monday, May 14, 2007 - link
What do shovels have to do with race?Stan11003 - Monday, May 14, 2007 - link
My big hope out all of this that the ATI part forces the Nvidia parts lower so I can use my upgrade option from EVGA to get a nice 8800 GTX instead of my 8800 GTS ACS3 320. However with a quad core and a decent 2GB I have no gaming issues at all. I play at 1600x1200(when that become a low rez?) and everything is butter smooth. Without newer titles all this hardware is a waist anyways.Gul Westfale - Monday, May 14, 2007 - link
the article says that the part is not a failure, but i disagree. i switched from a radeon 1950pro to an nvidia geforce 8800GTS 320MB about a mont ago, and i paid only $350US for it. now i see that it still outperforms the new 2900...one of my friends wanted to wait to buy a new card, he said he hoped that the ATI part was going to be faster. now he says he will just buy the 8800GTS 320, since ATI have failed.
if they can bring out a part that competes well with the 8800GTS and price it similarly or lower then it would be worth buying, but until then i will stick with nvidia. better performance, better price, and better drivers... why would anyone buy the ATI card now?
ncage - Monday, May 14, 2007 - link
My conclusion is to wait. All of the recent GPU do great with dx9...the question is how will they do with dx10? I think its best to wait for dx10 titles to come out. I think crysis would be a PERFECT test.wingless - Monday, May 14, 2007 - link
I agree with you. Crysis is going to be the benchmark for these DX10 cards. Its hard to tell both Nvidia and AMD's DX10 performance with these current, first generation DX10 titles (most of which have a DX9 version) because they don't fully take advantage of all the power on both the G80 or R600 yet. Its true that Crysis will have a DX9 version as well but the developer stated there are some big differences in code. I'm an Nvidia fanboy but I'm disappointed with the Pure Video and HDMI support on the 8800 series cards. ATI got this worked out with their great AVIVO and their nice HDMI implementation but for now Nvidia is still the performance champ with "simpler" hardware. The G80 and R600 continue the traditions of their manufacturers. Nvidia has always been about raw power and all out speed with few bells and whistles. ATI is all about refinement, bells and whistles, innovations, and unproven new methods which may make or break them.All I really want to wait for is to see how developers embrace CUDA or ATI's setup for PHYSICS PROCESSING! Both companies seem to have well thought out methods to do physics and I cant wait to see that showdown. AGEIA and HAVOK need to hop on-board and get some software support for all this good hardware potential they have to play with. Physics is the next big gimmick and you know how much we all love gimmicks (just like good 'ole 3D acceleration 10 years ago).
poohbear - Monday, May 14, 2007 - link
they dont make a profit from high end parts that's why they're not bothering w/ it? that's AMD's story? so why bother having an FX line w/ their cpus?