I wonder why he used the 74LS00 family instead of 74HCT00, even if he really needed the TTL thresholds? I forget if ISA even requires TTL levels. Is that a question of nostalgia, or is there a practical advantage of TTL over TTL-compatible CMOS in this context that I'm unaware of?
You cannot choose the source, these come mixed from ST, TI, and other manufacturers. I preferred the laser-engraved ones instead of the white ink ones just to have an uniform look.
The crystal oscillator needs something faster so it requires 74F04, and the link communication buffer requires 74F244 or 74AS244. These are more expensive, the 74F are 2 dollars each chip, and the 74AS are 4 dollars each chip.
i want all 64 bits with a write strobe and a 3ghz clock. let me blink leds by bitbanging /dev/mem
SCSI was already contending with the termination problem in the early 90s; low-voltage differential SCSI was in the SCSI-3 standard from 01995, 30 years ago, in order to hit 80 megabytes per second over the kind of multidrop (bus) parallel interface you're talking about. That's twenty thousand times slower than the main system memory interface on the latest amd64 servers.
At the point where you already had to go to low-voltage differential signaling to get reliable communication, your bus is no longer a useful GPIO interface for blinking LEDs.
But if you have a 50¢ 16-line GPIO expander chip like https://www.digikey.com/en/products/detail/kinetic-technolog... somewhere on the SMBus the board is already using for things like temperature monitoring, maybe for some other minor interface function, all that's required is to run its GPIOs to test points and document them. Not as fast as the ISA bus but plenty of power for simple digital interfacing.
taid9iK-•1d ago