Author: Wayne Lowrance
Date: 08:31:33 02/12/00
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On February 10, 2000 at 23:27:52, Robert Hyatt wrote: >On February 10, 2000 at 22:08:55, Tom Kerrigan wrote: > >>On February 10, 2000 at 18:11:25, Robert Hyatt wrote: >> >>>The basic clock frequency for a chip comes from adding up gate delays in a >>>path from X to Y inside the chip. If you go too fast, you latch data before >>>it settles. If you go too slow, you just go too slow. If you ramp up the >>>clock beyond spec, you _must_ do something to speed up the gate delays. One >>>way is to up Vcc. That ups the heat. Which kills the chip lifetime. You >>>can do various tricks to conduct the heat away (ie kryo approach). But no >>>matter what you do, you can't make the gates function much faster. In some >> >>This is not correct. >> >>Gates function faster at lower temperatures. >> >>As I said in a previous post, I wouldn't be surprised if a 1GHz Athlon @ -40C is >>more stable than a 750MHz Athlon @ 100C. >> >>-Tom > > >The physics don't support you there. IE gates don't function faster at >absolute zero, but the resistance goes to zero. I know of no physics law >that says electrical signals propagate faster at lower temperatures... > >Of course, you can ramp up the voltage to make them switch faster, and you >can make them smaller, because cooler temperatures combat the heat rise for >smaller junctions. But I sure don't see why they would switch faster. If >they did, Cray would have run his stuff at really cold temperatures since he >was speed-centric... Your partially correct. at these frequencies a piece of copper conductor, even exgtremely short connections has the equivalent circuit of a transmission line. Shorter means less intrinsic reactances and R and faster response to a step function input with less delay. Wayne
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