PCI and Expansion ROM

[Gilbert Yeung <gilbert@lanworks.com>]

All the messages regarding "Int 13 and the BAR" are interesting to us 
because we develop BootROMs for different NIC vendors. We have developed 
a number of PCI BootROMs (around 10) and came across several BIOS issues 
that I am listing below:

1) some BIOS do not check the Device ID in the BootROM PCI Data 
Structure. This causes a BIG problem for us and we see it as a violation 
of the PCI Spec. The Spec says

"If a ROM Is attached, then POST must search the ROM for an image that 
has the proper code type and whose Vendor ID and Device ID fields match 
the corresponding fields in the device"

2) on some of the BootROMs, we have to access the real physical ROM in 
extended memory during the INIT function. We use Int 15 Fun 87 and found 
it to be unreliable on some BIOS. If we do not run Int15 during the INIT 
function, everything would be fine. If there are any BIOS vendors in this 
mailing list, please make sure Int15/Fun87 is fully support during INIT 
time. 

3) some BIOS will NOT call an expansion ROM when the size of the BootROM 
is around 40K. A couple of systems actually hang. We started with a 64K 
ROMSize and gradually decreases the size until we get called. We check 
and there is enough free high memory on the system (we are the only one 
using high memory). We have to split our ROM into different pieces to 
ensure we will get called. 

4) we have seen an AMD SCSI Expansion ROM which shrink itself to a NON- 
2K boundary (runtime size). This throws off the BIOS alignment and all 
Expansion ROMs after that are not called. 

5) on some Compaq PCI machines, the Expansion ROM will be bypassed if we 
force the NIC interrupt to be a specific value (rather than let the BIOS 
decide). We found that when we are doing interrupt sharing testing. 

There are more issues that I can't remember. If there are any BIOS 
vendors in this mailing list and you have more questions, please respond. 
Regardless, PCI is still much better than Plug and Play  :>). 

thanks

--------------------------------------------------------------------------

Gilbert Yeung
Lanworks Technologies Inc
Voice: 905-238-5528 ext 135
Fax:    905-238-9407
-------------------------------------------------------------------------

´¤