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Politics : Formerly About Advanced Micro Devices -- Ignore unavailable to you. Want to Upgrade?

To: Charles R who wrote (68195)	8/9/1999 11:03:00 PM
From: AJ Berger	Read Replies (3) \| Respond to of 1579742

Is anyone working on a 200mhz memory bus bios for the Athlon? will the first machines out from IBM and Compaq be 66mhz, 100mhz, 133mhz or 200mhz memory buses?

To: Charles R who wrote (68195)	8/10/1999 10:48:00 PM
From: THE WATSONYOUTH	Read Replies (2) \| Respond to of 1579742

Cirruslvr <He confirms the Athlon's voltage - "The current specification of the 500 - 650MHz parts call for a core voltage setting of 1.6v, which is 0.4v less than the Pentium III's voltage 2.0v requirement."! I guess AMD will have room to jack up the voltage if that is necessary to get to 700MHZ> Charles R <I have been a little bit indifferent to the voltage issue so far but it is quite impressive what AMD has here. Given that AMD is rumored to be getting at least 750MHz on 0.25, they will have enormous upside potential in 0.18. Usually, one of the hits a design takes while moving to a new process is that it will have to operate at a low voltage which negates part of the benefit of moving to the new process w.r.t. speed. Athlon may not have to take that hit (other than the chips for laptop market) Process guys on the thread, do you care to comment? It's not clear to me what the limiting factor here is. The Athlon in .25um technology MIGHT be limited by the active power. It seems from the AMD web site that at 1.7V, a 650MHz Athlon could generate 54W maximum. Maybe the package can't handle too much beyond that. If they simply raised the voltage to say 1.9V they would easily reach perhaps 720MHz. However,since power goes as (CV^2 X freq), the power would increase by perhaps 40% to a likely unmanageable 75W. So if they are power limited, (CV^2 X freq = constant) they can only increase freq. by lowering capacitance. Thus, they must run at smaller channel lengths. This put demands on both the device design and process capability. So perhaps 22 million devices does cost you something. If they are limited to 1.7V because of power constraints, then, if they were clever, they would choose a gate oxide thickness which just meets 10 year reliability at 1.7V. This is probably around 27A-28A. This is indeed much thinner than Intel is running for their .25um generation which I believe is about 35A. That is why Intel can raise the voltage to 2V without a problem. They have a large gate oxide reliability margin at 35A (probably 30A is the limit at 1.8V) Given far fewer devices, Pentium runs at lower power even at 2V. Alternately, perhaps Athlon is also around 35A in .25um technology.Then they are leaving performance on the table if they are power limited to 1.7V. Now, Intel's .18um process supposedly will run 20A gate oxide. This should limit the voltage to 1.5V (reliability limit) unless Intel comes up with an improved gate oxide process. Given so much lower operating voltage, Intel's device design at 1.5V must improve dramatically (much shorter channel lengths). From what I've seen, it has. So at 1.5V Coppermine power should decrease quite a bit even at much higher (825MHz) frequencies. If AMD also goes to 20A, then they should also be limited to approx 1.5V. But this is only .2V below where they are now. So, at higher frequencies (say above 900MHZ) power may not decrease at all. They may have to run even lower voltages at .18um to lower the power. This will put much pressure on the device design and process which will have to push to shorter channel lengths to recover the performance. Please be aware there are a lot of assumptions here. But, this should illustrate some of the tradeoffs. I do think there is a downside in using 22 million devices. Hopefully for AMD, they can get around it.. THE WATSONYOUTH