So the FPU arrived, I installed it, reassembled the machine, and fired it up. It was...flaky. Random, inconsistent instruction and bus errors, etc. Finally narrowed it down the 16MB of RAM I'd replaced the original 4MB on the accelerator with. I put the original four 1MB SIMMs back in, and now it's rock-solid. The 4MB SIMMs I tried *should* be compatible, so maybe one of them is bad? I only have four 4MB 30pin SIMMs to try unless I want to take apart my accelerated Classic...and I don't. Anyways, this thing is currently working great in its original configuration plus an FPU, so I'm happy
logic board and accelerator reassembled (with flaky 4MB SIMMs):
some Speedometer benchmarks:
nifty MicroMac boot screen (sorry about the vertical video):