4 ms·

and heating up the chip to the point that it needed a cooling fan -- a COOLING FAN, can you imagine a CPU running so fast it couldn't cool itself on ambient air

by einr 5y ago

and heating up the chip to the point that it needed a cooling fan -- a COOLING FAN, can you imagine a CPU running so fast it couldn't cool itself on ambient air? This feels super nitpicky but I'm curious about your setup and if you're either remembering the clock speed wrong or if the fan was actually completely extraneous, because in fact neither of the common 40 MHz 486 parts, the Cyrix Cx486DX40 or the AMD Am486DX40, required a fan. The Cyrix one came with a heatsink, which was a rarity at the time. The first 486-class CPU that pretty much always ran with active cooling was the DX4/100. Even the DX2/66 could run fanless if you had half decent airflow.

myself248 5y ago
I'm certain of the clock speed, but I think you're right that the manufacturers alleged they were fine without additional cooling. (They considered it a bad look, and actually said that chips sold with fans were likely overclocked chips intended for a lower speed bin, or otherwise graymarket.) But consensus among everyone _but_ the manufacturers was that additional cooling couldn't hurt. (A representative opinion can be found in Upgrading And Repairing PCs, whatever edition was current at the time.) Running right at the top of Tcasemax wasn't good for longevity in terms of electromigration within the chip itself, nor for the capacitors and other components in the neighborhood. Thermal goop wasn't commonplace yet, but the little heatsinks and fans sold like hotcakes (har!) at the local computer shows. Plain aluminum heatsink, clear (polystyrene?) fan, with a holographic "CRYSTAL COOLER" sticker on top. I still see the fans around, but without the shiny sticker. The Am486DX-40 was my favorite chip. With a VLB video card (Trident 9400CXi) that worked well on the 40MHz bus, its pure pixel-pushing power ran rings around 33MHz-bus systems regardless of their core clock, and that included the P-75. I later got the impression that I lucked out with that Trident card, as almost everyone else with a 40 or 50MHz VLB machine had tales of woe and flakiness. If you're not already familiar with it, you'll likely enjoy this trip down memory lane: https://redhill.net.au/ig.html https://redhill.net.au/ig.html
- einr 5y ago
  Thanks for the reply! That is interesting and makes a lot of sense. Yes, running a 40 or 50 MHz bus made a huge difference, especially if you could get VLB graphics running reliably on it. I'm into collecting and tinkering with 486-era machines for nostalgia's sake and often i see things like DX2 or DX4 systems with plain cheapo 16-bit ISA graphics cards and think such wasted potential...
necovek 5y ago
I was pretty sure none of the 486 CPUs absolutely required a cooling fan (though I only had a DX2/66MHz): I remember Pentium II being the first CPU I've seen that absolutely required it (came with one integrated on the second computer I assembled for myself), and I distinctly remember having trouble testing an AMD CPU a year of so later on a computer I was assembling for someone else because... well, it wouldn't even POST without a CPU cooler. Luckily I did not fry it and after adding a cooler it worked just fine. I don't remember if AMD or Cyrix CPUs were worse though.

by einr 5y ago

myself248 5y ago

I'm certain of the clock speed, but I think you're right that the manufacturers alleged they were fine without additional cooling. (They considered it a bad look, and actually said that chips sold with fans were likely overclocked chips intended for a lower speed bin, or otherwise graymarket.) But consensus among everyone _but_ the manufacturers was that additional cooling couldn't hurt. (A representative opinion can be found in Upgrading And Repairing PCs, whatever edition was current at the time.) Running right at the top of Tcasemax wasn't good for longevity in terms of electromigration within the chip itself, nor for the capacitors and other components in the neighborhood. Thermal goop wasn't commonplace yet, but the little heatsinks and fans sold like hotcakes (har!) at the local computer shows. Plain aluminum heatsink, clear (polystyrene?) fan, with a holographic "CRYSTAL COOLER" sticker on top. I still see the fans around, but without the shiny sticker. The Am486DX-40 was my favorite chip. With a VLB video card (Trident 9400CXi) that worked well on the 40MHz bus, its pure pixel-pushing power ran rings around 33MHz-bus systems regardless of their core clock, and that included the P-75. I later got the impression that I lucked out with that Trident card, as almost everyone else with a 40 or 50MHz VLB machine had tales of woe and flakiness. If you're not already familiar with it, you'll likely enjoy this trip down memory lane: https://redhill.net.au/ig.html https://redhill.net.au/ig.html

einr 5y ago
Thanks for the reply! That is interesting and makes a lot of sense. Yes, running a 40 or 50 MHz bus made a huge difference, especially if you could get VLB graphics running reliably on it. I'm into collecting and tinkering with 486-era machines for nostalgia's sake and often i see things like DX2 or DX4 systems with plain cheapo 16-bit ISA graphics cards and think such wasted potential...

necovek 5y ago

I was pretty sure none of the 486 CPUs absolutely required a cooling fan (though I only had a DX2/66MHz): I remember Pentium II being the first CPU I've seen that absolutely required it (came with one integrated on the second computer I assembled for myself), and I distinctly remember having trouble testing an AMD CPU a year of so later on a computer I was assembling for someone else because... well, it wouldn't even POST without a CPU cooler. Luckily I did not fry it and after adding a cooler it worked just fine. I don't remember if AMD or Cyrix CPUs were worse though.