440BX and SDRAM

[Richard Smith]

Erik Jansson wrote:

> 
> 1. I can't manage to initiate more than 128 MB of SDRAM (ramtest 
> fails). I've tried a lot of different types and brands of memories, 
> standard DIMMs and SO-DIMMS, different sizes, etc. I'm thinking it
> has something to do with "double sided" memory (or dual "module
> banks" or whatever terminology you choose). Buffer strength settings
> maybe? But I've tried the same settings as the standard BIOS uses
> (which sets up the memory correctly btw) and still no go. Some
> obscure bit in some obscure register?

Are you trying 2 128 MB DIMMS or a 256 MB DIMM?  The 440bx does not
support 256Mbit dram so most 256 meg dimms won't work.  Of course now 
that I re-read you say the standard bios works so its probally not that.

What bus speed are you running at?  Intel claims that buffer strength 
becomes very critial at 100Mhz the board I did most testing on only runs 
66Mhz and the project that used a 100Mhz version died so I don't have 
much data on the subject but thats the word I got from intel.

I don't recall any non-documented registers.  Once I figured out the 
difference between the standard bios and what Linuxbios was doing our 
ram problems went away.    I guess it's still not totally fixed though, 
Bummer.  That's very tedious stuff to debug.  I can't help much either 
since our board only has 1 DIMM.

So things up to 128 Meg work but > 128 fails?

-- 
Richard A. Smith
rsmith at bitworks.com