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#21
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#22
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On Fri, 13 Aug 2004 12:54:14 +0000, Mike Andrews wrote:
In (rec.radio.amateur.homebrew), Fred Bloggs wrote: Paul Burridge wrote: On Fri, 13 Aug 2004 03:49:15 +0000 (UTC), (Ken Smith) wrote: Theres no problem getting 10mA to flow in a FET with Idss of 5mA. Just apply a positive bias to the gate. I've had as much as 2 or 3 A flow through a JFET this way. How many mS did the Fet last? I suppose you could always stand there with a can of arctic spray directed on it, but I doubt the customer would be impressed. ;-) Actually there have been systems produced that did run quite hot and were arranged with a liquid nitrogen drip onto the electronics to keep things cool. One model of Seymour Cray's computers ran with the logic immersed in a bath of chilled Fluorinert or some such, with a fairly hefty pump to keep the coolant recirculating through the chiller. Many years before, IBM was going to use a CFC (FC86, IIRC) in much the same way. The logic modules were about 4" cubes with a multi-layer (50-60, can't remember) ceramic substrate with 100 logic chips on one side, a water-filled cold-plate on the other, and filled with the CFC. Heat was removed from back-side of the chips by boiling the CFC. I worked on a logic tester in '75 that immersed the un-encapsulated substrate into a bath of CFCs so it could be probed. Unfortunately, boiling the CFC also distilled it, leaving any contamination on the chips. The result came to be known as the "black plague". Because of the "black plague" the "LEM" (Liquid Encapsulated Module) was replaced by a similar looking (though shorter) "TCM" (Thermal Conduction Module) which used pistons on the backside of the chips (increased to 121 chips) to transfer heat (10W per chip, 1200W total) to the cold-plate and filled with helium. The TCMs were used throught the '80s and early '90s for the high-end ECL systems. -- Keith |
#23
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I read in sci.electronics.design that Keith wrote (in
) about 'Error in textbook?', on Sat, 14 Aug 2004: Unfortunately, boiling the CFC also distilled it, leaving any contamination on the chips. Sulfur hexafluoride might have been better, but it's probably more costly than CFCs were. -- Regards, John Woodgate, OOO - Own Opinions Only. The good news is that nothing is compulsory. The bad news is that everything is prohibited. http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk |
#24
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In (rec.radio.amateur.homebrew), Keith wrote:
Unfortunately, boiling the CFC also distilled it, leaving any contamination on the chips. The result came to be known as the "black plague". Because of the "black plague" the "LEM" (Liquid Encapsulated Module) was replaced by a similar looking (though shorter) "TCM" (Thermal Conduction Module) which used pistons on the backside of the chips (increased to 121 chips) to transfer heat (10W per chip, 1200W total) to the cold-plate and filled with helium. The TCMs were used throught the '80s and early '90s for the high-end ECL systems. Yep. I've got a TCM somewhere at home; I need to take a pic of it for my web page. IIRC, it has 1024 pins, and the largest ZIF socket I've ever seen. The cold plate on the TCM is about 4.5" square, very smooth, and designed to go on a larger water-cooled manifold with some dozens more TCMs, all getting water from a chiller. They're called "wet-frame" machines by a lot of us who dealt with them, and especially by those of us who had a leak develop somewhere in the cooling system. Nowadays one TCM's circuitry fits on a single chip, at a meager fraction of the TCM's dissipation, and is enormously faster, so that (for 9672 hardware, anyway) IBM ships the machine with a bunch of CPUs and licenses you the code to turn on as many as you're paying for. If you want more than ship in the base machine, they'll install another dozen pretty cheap. And the homebrew and design connections: They're sure not homebrew, and they're more than one designer can do. -- Mike Andrews Tired old sysadmin |
#25
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On Sat, 14 Aug 2004 18:24:14 +0100, John Woodgate wrote:
I read in sci.electronics.design that Keith wrote (in ) about 'Error in textbook?', on Sat, 14 Aug 2004: Unfortunately, boiling the CFC also distilled it, leaving any contamination on the chips. Sulfur hexafluoride might have been better, but it's probably more costly than CFCs were. Cost? Dunno. I do know that we were paying $50/qt (IIRC) for the stuff in '75. I wouldn't think a sulfur/fluoride brew could be made any "cleaner" than CFCs. THe problem was the contaminants. -- Keith |
#26
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On Sat, 14 Aug 2004 20:53:24 +0000, Mike Andrews wrote:
In (rec.radio.amateur.homebrew), Keith wrote: Unfortunately, boiling the CFC also distilled it, leaving any contamination on the chips. The result came to be known as the "black plague". Because of the "black plague" the "LEM" (Liquid Encapsulated Module) was replaced by a similar looking (though shorter) "TCM" (Thermal Conduction Module) which used pistons on the backside of the chips (increased to 121 chips) to transfer heat (10W per chip, 1200W total) to the cold-plate and filled with helium. The TCMs were used throught the '80s and early '90s for the high-end ECL systems. Yep. I've got a TCM somewhere at home; I need to take a pic of it for my web page. IIRC, it has 1024 pins, and the largest ZIF socket I've ever seen. I think you'll count a lot more than 1024 pins. The ones I worked on int the '70s had 1800. There were 1280 signal pins (I rember that name because of the logic tester - the LT1280). The cold plate on the TCM is about 4.5" square, very smooth, and designed to go on a larger water-cooled manifold with some dozens more TCMs, all getting water from a chiller. Twelve TCMs for each processor, and nine for each channel (for the 3080s). A system could have upwards of a hundred of these beasts in it. Later sytems had fewer since the logic density increased. ...which is what ultmately killed them. The infrastructure was simply too expensive for the quantity needed. They're called "wet-frame" machines by a lot of us who dealt with them, and especially by those of us who had a leak develop somewhere in the cooling system. ****ers, eh? I was once tasked to design a "leak detector" for exactly thi sproblem. I brought in the guts out of a toilet (complete with copper float) and told them to put these under the floor with a switch. Come on! Detect a leak in a pipe a few hundred feet long passing many gallons per minute? Nowadays one TCM's circuitry fits on a single chip, at a meager fraction of the TCM's dissipation, and is enormously faster, so that (for 9672 hardware, anyway) Note that the first CMOS machines were slower than those they replaced (in direct violation of IBM's "prime Directive"). THough they were significantly cheaper and with more processors (loophole alert). IBM ships the machine with a bunch of CPUs and licenses you the code to turn on as many as you're paying for. If you want more than ship in the base machine, they'll install another dozen pretty cheap. "Install"? ;-) They'll enable as many as you want, for as long as you are paying. We called this "Rent-A-MIP". THere is even a crypto unit in there if you want to use it. And the homebrew and design connections: They're sure not homebrew, and they're more than one designer can do. Yeah, there were a few designers doing this stuff. ;-) -- Keith |
#27
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Keith wrote:
On Sat, 14 Aug 2004 18:24:14 +0100, John Woodgate wrote: I read in sci.electronics.design that Keith wrote (in ) about 'Error in textbook?', on Sat, 14 Aug 2004: Unfortunately, boiling the CFC also distilled it, leaving any contamination on the chips. Sulfur hexafluoride might have been better, but it's probably more costly than CFCs were. Cost? Dunno. I do know that we were paying $50/qt (IIRC) for the stuff in '75. I wouldn't think a sulfur/fluoride brew could be made any "cleaner" than CFCs. THe problem was the contaminants. Yeah, and whether you're working with a liquid or gas, it's the contaminants that make it dirty. I'd think a gas could be cleaner already just by not dissolving a bunch of solids, although the solids in suspension can be even smaller than in a liquid. But those aren't going to condense out. They might collect as dust, but if that's your problem, then you have a lot worse problem than contaminated fluid! I guess my point is, it wasn't the CFC's fault that it was contaminated. And, FYI, AIUI, SF6 is really quite inert. You make it sound like fire and brimstone, for heaven's sakes! ;-) But it has raised a good question - which makes a better heat transfer agent? Helium or SF6? (gases only, of course ;-) ) Cheers! Rich |
#28
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