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Digital-Daily : Video : ati-radeon-x800xt

ATI Radeon X800 XT (R420): Extreme force

Author: Andrey Kuzin
Date: 09.05.2004


ATI Radeon X800 XT
GPU chip ATI R420
Memory 256 Mb; GDDR3 1.6ns
Core/Mem: 520/1120 MHz
Category: Hi-End
Price: $500

Remember how many score points did the fastest VGA give on the date 3DMark2003 was issued? I don't either. What I remember is that it was not much at all. In fact, the score was so low that gamers of all the world were about to anathematize that benchmark. At least, it failed to be a testing sport discipline. Now it will - both R420 and NV40 easily got over the important 10000 score points bar at one stroke.

Having run through all the tests and got round to writing this review, I was clearly aware that on clicking the intriguing text label "ATI Radeon X800 XT (R420): secret weapon", the reader would pursue the only goal - to find out "who on earth is the winner this time?" And you are absolutely unwilling to browse through the ten pages of the review while reading 50 k of text. Let's comply with a request of the most impatient and, breaking the rules of the tragedy genre, lay our cards on the table in the second paragraph:

Is it any easier now? :-) Perhaps, but not for all. This should frustrate especially those who recently bought a Radeon 9800XT or GeForce FX5950Ultra. As was promised, today's novelties indeed demonstrate a two-fold lead over the yesterday's champions at the same price as much as $500.

ATI R420 Graphic Chip

R420, the first in the line of ATI's Hi-End chips is manufactured following the 0.13 mk process technology at lithographic production lines of TSM— (Taiwan Semiconductor Manufacturing —ompany). Formerly, ATI trained a lot with much cheaper RV360 while expecting the production cost reduction.

ATI R420
Manufactured on the first week of April 2004.

ATI X800 review:
(published 4 may `04)
[H]ard OCP.com
Hardware Analysis
Driver Heaven
PC Perspective
Lost Circuits

Physically, it is absolutely impossible to arrange 160 mln transistors making up R420 without increasing the 0.15 mk chip area, so transition to the 0.13 mk technology was inevitable. This transition by ATI was in many ways paid by the sweat and blood of its competitor, NVIDIA, who had started experiments with 0.13 chips through releasing NV30 at the same TSMC grounds as early as in the summer of 2002 once the first Taiwanese production line for the process technology was built. The new process technology is the seven circles of hell which NVIDIA had to go through, but when the efforts were completely exhausted, the company transferred production of its chips over to IBM facilities and all started over again (currently, it is again transferring all to TSMC).

For ATI chips, such an urgent transition was not so critical. Their R300 core (which served as the basis for further R360 and current R420) had fewer transistors (115 mln) owing to the optimum chip architecture. Those transistors quite easily fitted within the reasonable dimensions of chips manufactured following the 0.15 mk process technology. But NVIDIA would persistently fail to fit within the dimensions starting with the first FX chip, that's why they suffered a lot with the urgent search of the most recent process technology.

The video chip architecture rarely undergoes a "radical" change. So it's more than naive to wait for absolutely new chip every 9 months. It's also naive to assume that a team of engineers takes on a new chip upon finishing a project. NOTHING OF THE KIND. Both ATI and NVIDIA have at least three teams like these - one is developing a current chip declared in the roadmaps, the second is doing the next, and the third team is working at a forward-looking goals to achieve in many years to come ...

Therefore, having completed R300 (Radeon9700 Pro), the company teams immediately started work at doubling the number of pixel and vertex pipelines on the base of that successful core. Why is R320 mentioned all the time? All is simple - before its emergence, ATI was hanging by a thread: at performance, the hi-end ATi Radeon 8500 was able to oppose only the cheapest Ti4200 ($200), the sales dropped "below the sea level", no profits came - only losses, and the number of low-end chips exceeded all the reasonable limits; a special driver was needed to support for every card; the marketing division seemed to be headed by rookies, and the top management had no better to do but mark the company account balance from day to day. The money was melting.

All was thrown at the last resort - the development of a new chip, R300. If now Intel had to develop a new processor architecture for the mainstream market, the company's well-being would shatter immensely. The development costs for every new product by Intel, AMD, ATI and NVIDIA are currently beyond any reasonable limits. If we pronounce these figures to our (Russia's) government, they would turn green with greed and drown themselves because of the sorrow.

So, speaking that ATI and NVIDIA "released new chips", we've got to be clearly aware of what is really new in them ... Novelty is varied. Currently, no one would dare to change the finely-woven chip architecture - it's too costly. Therefore, the only possible options are addition of some new functionalities, overclocking the core to some extent, pipeline optimization, and... the most radical thing - increase in their number.

It's just the number of pixel and vertex pipelines that has been doubled in today's R360/NV40, which is not that frequent these days.

R360 Block Diagram

All the blocks that have undergone changes are highlighted in red. Six units of vertex programs (instead of three as was before) theoretically prepare 750 mln polygons per second. For comparison - NV40 demonstrates 600 mln polygons per second due to the lower operating frequency of the chip.

And the 16 pixel pipelines are able handling 80 shader instructions per cycle in parallel at 192 GigaFLOP performance, with the theoretical fill-rate over 8.8 gigapixels per second.

Documentation (PDF):

The pixel shader pipeline is made up of two vector-driven and two scalar ALU. Plus one address ALU and a special F-Buffer unit responsible for handling longer OpenGL shaders.

The spice of the R420 technology is the full processor scalability and the possibility to create 16-, 8- and 4-pipeline configurations of the pixel pipeline for processors of all the market niches.

The complete description of the processor architecture takes up tens of pages and merits a special consideraion, but those who are curious may download the PDF document Architecture_Final.zip (1 MB).


  • ATI R420 Graphic Chip
  • ATI Radeon X800 XT Video Card Features
  • GDDR3 Memory
  • Technologies. Demo "Ruby"
  • "Cheating" and "optimizations
  • Tests: synthetic benchmarks
  • Tests: gaming applications
  • R420 vs NV40: first glance
  • Final Words

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