Does the BIOS save SPD tables from good DIMMs, and then apply those settings to other DIMMs?

My i430TX enters POST with the normal beep, then exits to a quiet continuous beep. It terminates with continuous beeps with or without DIMMs installed - I have tried various permutations.

Then, I noticed a similar behaviour on my iMac Duo-Core with two SODIMMS. The iMac boots with 1Gb + 2Gb installed. It drops out of POST with 2Gb + 2Gb, and drops out with only 2Gb also. It seems to rely on that 1Gb stick to make sense of the 2Gb sticks.

And, I seem to remember (decades ago) something similar about the i430TX being very picky about DIMMs. I seem to remember BIOS config was done using a temp donor DIMM from another PC, then removing the donor after config is saved.

I've no explanation.

I do want the i430TX to complete POST, and I'd like the iMac to use 2Gb+2Gb. Any ideas?