I had one of those AMD 486DX40's and it was a screamer. Yes, very picky about VLB card choice and even placement; we had a big multi-IO card (possibly made by

I had one of those AMD 486DX40's and it was a screamer. Yes, very picky about VLB card choice and even placement; we had a big multi-IO card (possibly made by DFI?) and a Trident SVGA card, and it took a few days of shuffling and benchmarking and stability testing to find the optimum arrangement. ISTR that if the IO card was closest to the CPU, it simply wouldn't boot about half the time, and it was unstable if it did. Putting the IO in the third VLB slot and the video card in the second, leaving the first empty, seemed to be the best arrangement. And it left the IDE cables reasonably close to the drives, so that was a win. But once we got all the drivers loaded for that IO card and stuff, it absolutely flew. Ran rings around a lot of Pentium/90 systems because their 33MHz bus just couldn't keep up, and in the days before GPUs, pushing pixels into video RAM was a contest of raw bus bandwidth and very little else. We eventually had quite a lot of drives on that machine, so UDMA/33 moved a lot of bytes while still leaving spare bus cycles for overhead. I tried overclocking it to 50MHz a few times, and the IO and VGA cards were both capable, it was the RAM that shat itself. The upper 3MB of RAM would just vanish, leaving only 1MB, which was honestly a fair tradeoff for some things -- I'd boot in that config if I had a lot of PKZIP to do, or for rendering fractal graphics, which didn't use a lot of RAM but really appreciated the extra clock speed. Then clock it back down and reboot to use the results of those operations. Underclocking was also nice, and something I did frequently, so I could unplug the CPU fan and enjoy some quietude during a long BBS file transfer, which certainly didn't need much CPU grunt. The mobo clock generator didn't mind being re-jumpered while the system was on, and going from 40MHz to 16MHz (I think) was a simple matter of adding or removing one jumper cap, as I recall. I could reach through the floppy-drive opening in the front of the case and do this after a download started. Then switch off the monitor, and listen to the quiet tick-hiss of interference on my FM radio, which picked up just enough of WHYT 96.3 in the basement that I could listen to some alt-rock while also being aware of the UART ISR being hit. When the ticking stopped, the modem was idle, turn the monitor back on, jumper the CPU back up to speed and plug the CPU fan back in while the CRT warmed up, and get on with unpacking the file.