Graphics - Published on Wednesday, 30 August 2006 20:22 Written by Marcus Hultin
When ATI was about to launch its X1950XTX, it invited the press to a conference in Berlin. The highlight of the agenda was Joe Macri's presentation of GDDR4. We received information and were enlightened that Joe Macri is a rarely seen guy you don't want to miss. Joe Macri is simply an ATI coworker that also sits on the JEDEC board of directors. The day before the conference we, a couple of editors and ATI employees, decided to head out in the night of Berlin to get some food and drink a few beers. It didn't take long before we all understood that Joe Macri is truly passionate about his work. As soon as he gets a question he expands it and replies with a very simple answer, sometimes it got a bit spooky considering how well he can articulate himself without having anything prepared. He also has a special ability to make everything sound very simple. I don't think I've ever heard so many metaphors spoken at the same table as when Joe Macri tells ”the story of GDDR4” at a small restaurant on Fredichstrasse in Berlin. Unfortunately the story is way too long for us to be able to present it here, but we can at least start with telling you that GDDR4 has been the goal they set up five years ago, when they first started developing GDDR.
The fundamental changes that have been made since GDDR3 are reducing the VDD noise (voltage) and optimized the signals in general. They've also created something called Double Pumped Address Bus. A new technology that makes it possible for GDDR4 to use only half as many physical connections (pins, or balls) to communicate. The now available connections are instead use for power which opens up the possibility for higher speeds. DPAB in itself also contributes to a slightly reduced power consumption. In other words, the goal has been to deliver faster memories with lower power consumption. GDDR4 brings about 30% lower consumption than GDDR3 at the same frequency. Something they've been able to achieve thanks to a number of improvements of the communication and power consumption.
The chip used with our X1950XTX are made by Samsung and ranked at 0.90ns. They use 1.9V which is slightly lower than what we've seen with 1.1ns ranked GDDR3. The first tests show that the memory overclocks divinely at default voltage. 1143MHz (2286MHz DDR) is achieved without any fuss. Unfortunately we can't set the frequency any higher with the overclocking tools that are available today. We hope that Mikael at TPU, the creator of ATItool, will solve this problem soon so that we can really test the potential of these memories.
We will continue with testing the memories' efficiency relative the GPU on the next page.
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