I am sure those of you who have
recently purchased cards in the X1800 family are quite thrilled that
ATI has managed to launch a refreshed product line just three scant
months later--that is those of you who managed to track down one of
the elusive X1800 cards. ATI was delayed in their launch of the X1800
line, based on the R520 core, due to production issues. Because of
that setback, they had to choose between delaying the X1900 series, or
getting back on schedule. With the negative press they were getting
about the scarcity of products on shelves, the term “paper launch”
was fresh in everyone's minds this go 'round. The added determination to
hard launch the X1900 line payed off as we actually saw X1900XT's and
X1900XTS's on store shelves as early as two days before the actual
launch.
R580 Architecture
So many readers skip the tech
features of the GPU architecture in these reviews that we have chosen
to just give a brief overview of the new features for core refreshes.
Have an opinion on the subject? Discuss it here.
The days of pointing out clock/memory
speed and pipelines when discussing video card performance have come
and gone. New buzz words are being added with each generation and
transistor counts climb ever higher (a 20% bump this time out) to
numbers that are nearly impossible to get your head around. For
those of you really interested in the complex nuts and bolts, I
suggest ATI's web site and a white paper guaranteed to put you to
sleep faster than downing an entire bottle of Lunesta. With that in
mind, we are going to briefly cover some of the highlights, then get
to the benchmarking.
ATI has increased the number of
ALU's/Shader Processors from 16 to 48-- effectively tripling the R580's
arithmetic performance as compared to the R520. This accounts
for the bulk of that 20% boost in transistor count previously
mentioned. It also helps the pixel shader performance a great deal,
leading to the biggest enhancement of the R580's core performance
gains over the R520.
Higher Z (Hierarchical Z) support on
the R580 also got a nice boost with 50% more on-chip memory.
This should really show up in the higher resolutions.
ATI has also added a new technology
they are calling Fetch 4 that is designed to accelerate shadow
mapping. Worth noting is that Fetch 4 needs to be implemented by
game developers before end users will see any benefit from it.
X1900 Product Line
Specs at-a-glance (X1800XT included for reference only)
Card
X1800XT
X1900XT
X1900XT Crossfire
X1900 AIW
X1900XTX
Clock Speed
625 Mhz
625 Mhz
625 Mhz
500 Mhz
650 Mhz
Memory Speed
1.5 Ghz
1.45 Ghz
1.45 Ghz
960 Mhz
1.55 Mhz
Pipelines
16
16
16
16
16
Shader Processors
16
48
48
48
48
Once again, the changes in the R580 architecture do not vary that much when compared with the R520. It’s also based on a 90nm fabrication process and it consists of 384 million transistors. However, the R580 receives a major boost in pixel processors as it contains 48 of them compared to the 16 on the R520 core. Other than that, the specs sheet looks very similar to the R520 core, and as you can see in the images above, the X1800XT and the X1900XT/XTX are virtually identical on the outside.
For those of you contemplating the X1900XTX who are concerned about running it in CrossFire--don't be. You can run asynchronous cards without the faster card being clocked down.
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