I was putting in a digikey order anyway, so I just ordered the caps, aside from the two large ones, that is.

I tested the Baby screamer with a different CPU, however the result was the same as before.

It has recently come to my attention that there exist two speed jumpers on my AMI Mark V Baby Screamer motherboard, Rev. B. Rev. A boards don't have these. They are J35 and J37. These jumpers are not well documented in my printed manual, dated 11/14/91.

A table on the retroweb https://theretroweb.com/motherboards/s/ami-ma … r-s42#downloads suggests that:

FSB...............J35............J37
25 MHz........2-3............open
33 MHz.........2-3............open
40 MHz........1-2.............closed

I currently have the setting for 33 Mhz set. I wonder if this has something to do with not being able to clock-double over 66 MHz.

However, an updated PDF manual from 9/11/92 contradicts this, stating,

FSB...............J35............J37
33 MHz.........2-3............open
40 MHz........1-2.............open

In my manual dated 11/14/91, there no mention of J35, but there is one deceiving note concerning J37 in Appenix A, page 87:

140 MHz Operation
21. For 64K cache, U38 is not required. J37 must be shorted.
3
4The remaining [cache] sockets - U31, U32, U34, U37, U39, U41, U42, U44, U45, U46, and U47 become 16K x 4 12 ns SRAM.
5
62. The 256 KB cache option at 40 MHz is not present because 64K x 4 12 ns SRAM is not yet available.

In the past, I ignored this line because note number 1 sounds like J37 is to be shorted if using 64K cache, however, it may be that J37 is to be shorted if FSB is set to 40 MHz. There are a lot of typos in the manual in general.

So which information is correct?

I ran some benchmarks at 66 MHz and noted that shorting J37 reduces the memory read throughput from 14.8 MB/s to 12.1 MB/s (Cachechk). Moving J35 from 2-3 to 1-2 had no measurable impact. I plan on playing with these two jumpers further to see if I can get 2x40 Mhz to light up, rather than running the board at 2x33.