[OpenBIOS] flash ram on 440gx

[Steve and Sue]

Not sure whether I am answering your question or not, but I will give some
info on BIOS ROM mapping that may be of use:

As  a rule PCI chipsets decode two address bands (sometimes three), accesses
to either will drive the BIOS chip select with the upper address bits
stripped. Usually these bands are the upper 128 Kbytes of the first Meg and
512k or more at the top of address range, i.e. 4 Gbytes, (some also decode a
band at the top of 16 Mbytes for 80286 compatibility).

So in real mode (DOS mode) you can usually only access the upper 128k of
your ROM, however the programming registers on many Flash devices are at the
low end of their address range. So you must switch to protected mode (which
can be done from DOS), enable all BIOS decodes in the chipset (some are
default disabled) and program the Flash using addresses at the top of 4
Gbytes.

Often the whole of the Flash part is not used, 128 - 256k is typical and
this includes your Video BIOS etc. A commercial BIOS will switch to
protected mode (or big real) to gain access to the remainder of the ROM and
copy that code down to RAM for execution.

Regards, Steve


----- Original Message -----
From: Ronald G. Minnich <rminnich at lanl.gov>
To: <openbios at elvis.informatik.uni-freiburg.de>
Sent: 22 January 2000 00:36
Subject: [OpenBIOS] flash ram on 440gx


> the manual I did find for the ms440gx shows the flash ram at the top of
> 32-bit memory, i.e. at fff00000-ffffffff
>
> THere is nothing yet at intel showing the l440gx motherboard ...
>
> ron
>
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