Right. SCSI 1/2 are collections of standards and no device implements all of them.
Trying to improve the I/O performance of a 16MHz SE/30 is probably a lost cause.
JDW benchmarked SE/30 disk performance, showing significant gains with 030 and 040 accelerators.
Timing the duplication of a...
Very nice! I've been using THINK C 5 on a Centris 610. The 1152x870 display is easy to work with and compile times are reasonable. I test on monochrome Macs via LocalTalk, but I wouldn't want to develop on them. Here's something from 1995:
Those are low, but I doubt they're causing a problem.
Here are the lines on the SCSI controller that reach other ICs. The ones in cyan go to the CPU. I couldn't find any other reference to /IRQ in the schematic. I did trace it to pin 14 of UI6 (which I also couldn't find in there) on a spare...
Those voltages look OK and show the bus is idle.
Check the pins of the controller for electrolyte and corrosion. The nearby rail caps often leak on to it.
Swapping or reflowing the SCSI controller is what I'd try next.