On Tue, 6 Feb 2001 22:33:18 -0700 (MST), Ronald G Minnich wrote:
>On Tue, 6 Feb 2001, Richard A. Smith wrote:
>> Our first hurdle was that the Southbridge was ignoreing the reset
>> vector. Walking all the lines showed that all was well the processor
>> was issueing (0xFFFF0). Eventually we went ahead and looked at the
>> rest of the lines and found that they were all high as well except for
>> the A20 line which we thought was normal.
>
>My guess then is that A20 was being masked. What was the value of the A20
>Mask line before you cut it? If it was 0, then A20 was being gated, I
>guess.
>
Yes it indeed was being masked. That's why we cut it so that it would be unmasked.
>> We double checked that we had it hooked up just like the Intel ref design.
>
>Well, those ref designs are always just that -- ref. Any errors are your
>trouble.
Ugh.. It's not going to be pretty if we can't use the reference design as a reference.
In
this case the results are contridictory to what all the documentation seems to suggest
so
even double checking against the datasheets didn't help.
>> 2) Why does the southbridge only respond to addresses in the
>> 0xFFFFxxxx for BIOS when the data sheets seem to indicate that both
>> ranges should be decoded.
>
>I don't know BUT: do you care? You don't really need those low-order
>addresses for linuxbios. So if you have a mode that works, I would use
>that.
Yes but we need to know that that indeeded was the issue and why it wasn't working
like the
datasheets suggest. Otherwise we may just be covering up another problem that will
come back
an bite later. Those bites are usually much more painful. If reset dosn't work like
suggested then what else is on the horizon?
>Also, are you sure that it is not responding to ffff0? I don't think
>you've issued that address, just fffff000
>
Hmmm.. good point the address tested was 0xffeffff0 which didn't work and 0xfffffff0
which
did.
So what is the general concensus on what addresses(s) ARE suppossed to work for reset
vectors.
--
Richard A. Smith Bitworks, Inc.
[EMAIL PROTECTED] 501.846.5777
Sr. Design Engineer http://www.bitworks.com
