The VLB Pentium board I had used the opti 82C571/82C572 chipset. It was also extremely picky about memory combinations like your board. I was never really able to find much information on the chipset in this board. It was interesting though in that it could support both 486 and Pentium CPUs. I am pretty sure that this must have been the first VL Pentium chipset from opti.
The chipset on your board is called "Opti Premium" as you can see on the chips. I believe that one was fairly common at the time. I've never used one myself though.
There is a 3rd Opti VL-Pentium chipset I am aware of called "viper". I'm not actually sure if it was ever released, but I remember reading a lot about it in the early 90s. I'm not sure if it was something that came before or after the Premium chipset.
As you said, there may be others as well.
You should keep trying with the AMI board. AMI made pretty good quality stuff, and they usually had pretty good memory throughput when configured correctly.
"Will the highways on the internets become more few?" -Gee Dubya
V'Ger XT|Upgraded AT|Ultimate 386|Super VL/EISA 486|SMP VL/EISA Pentium