System is still chugging along with memory testing, no failures but did receive the out-of-memory error in FAST mode.
What should the voltage level be for ISA bus clock? TTL-compatible?
From looking at the schematic, it looks like CLK is the output of IC 39, which is a 74ALS04BN on my board. The datasheet says "vOut" is -0.5 to Vcc on that chip.
Why is there such a broad range of values for "vOut"? Maybe this is a stupid comment, but is it related to the "response" time, does it take a few microseconds for the IC to achieve full Vcc output level and it can't because we're switching too rapidly? Would faster logic like AS or S change this?
Ahah, from Sergey's page:
IC U39 74F04, 74ACT04 1
Mouser 595-SN74F04N, 595-SN74ACT04N
Note: This IC should have higher output current (about 20 mA), 74LS04, 74ALS04, or 74AHCT04 can be used, but it might result in stability issues especially on higher CPU frequency.
Interesting. How'd I miss that?