Strange memory detection on P6DBE

Hi all. I have bought a second-hand SuperMicro P6DBE (Ver.3.0)
motherboard with two P-II-350 CPUs. It works fine... with one small
exception: it refuses to detect my memory. I have two 256MB PC133
modules (by NCP). They were tested on other machine. Each of them
detects as only 128MB on this motherboard. 32MB PC100 Hyundai module
detects and works fine. I tried turning BIOS option "Memory autosizing
support" (or whatever it is called) on and off, updating BIOS and
tweaking other options with no luck. Things get really strange when I
install all these modules at once (256x2+32) -- all installed memory
(544MB total) detects without questions. Motherboard refuses to boot,
though -- both Windows 2000 SP2 and Red Hat Linux 7.3 (2.6.0-test5
kernel) crash at the beginning of bootup. I'm not surprised by this --
I think I have read in manual that only 512MB of plain SDRAM can be
used, but why they are detected, then? I hope someone can help me
here.

 

I do not have a P6DBE, but I do have a P6SBA in which I tried to put 256-
MB PC133 DIMMs, and only 128 of each memory module was recognized. The
brief research I did on the problem led me to believe that PC100 and
PC133 modules are internally configured differently so that only half of
the memory in each PC133 DIMM is recognized by this series motherboard.
This is probably because of the chipset generation. So, my guess is that
you need to get true PC100 DIMMs if you want the full recognition of the
memory by your motherboard. Good luck.

(uav) wrote in @posting.google.com: