I have two BigRAM+ cards. I just acquired a ZZ9900 and had this itch to see the Amiga memory at near AutoConfig-max, so I put both BigRAM+ in the A4000T. It doesn't seem to like one of the cards.
Host is an A4000T, TekMagic (ultrasound accelerator model) 68060/64MB/60MHz (Int Clocking) 2MB/16MB on the motherboard, Buster-11 / RAMSEY-07
Other expansion: X-Surf 100 in the 2nd furthest slot, ZZ9900 in the closest slot (to the CPU area).
BigRAM+ #1, gTanJ, has a 50MHz clock, and is generally reliable in the system. I have had it in either one of the two slots between the above cards.
BigRAM+ #2 DTarP, has a 60MHz clock, and is notably unreliable in the A4000T. If it doesn't toss up a Bad entry on early startup, the memory doesn't register and AutoConfig is not passed along most of the time to the ZZ9900. Remove it, and all is back to as expected. Slot chosen really didn't matter.
Note: - I have been running the card with the 60MHz clock fine in an A3000D/25 with Buster-11 and an AmigaNet card (my software Dev system) without issue. This was the first time I actually compared the two cards side by side. I had encountered the problem some time ago with presumably the 60MHz card, but I never chased it down since I picked up the second card somewhere, and they were working in their respective systems.
The 60Hz clock part is a smaller can vs the 50Mhz. Neither board looks like it was modified by anyone. I gave it a decent compare under my lighted magnifying glass. Aside from some different numbers on the middle 2 lines of the Xilinx chip, and the clock part, the boards look identical down to the memory chip and all passive parts.
Any guidance regarding the picky card? I'll probably leave it in the A3000D, but if something can be done about it, it would be nice to know.
Edit: The 60MHz clocked board also seems to behave in an A4000D (earlier rev) 2MB/16MB, Buster -11/Ramsey 07, with a T-REX II 68060/128M/66MHz CPU card (Int clocked).