Claiming 1M when using 8K

[Bob Huebner <BOBHU@Attachmate.com>]

We have designed a PCI Adapter that requires 8K of memory space and 16 
bytes of I/O space for a PC-based application.
When the memory and I/O BARs are programmed to take 8K and 64 bytes 
and the bits are set to allow them to be placed
'anywhere in memory', we have observed one BIOS that puts the 8K 
memory space below the 1Meg limit.

Since this presents the problem of a possible conflict with Legacy ISA 
adapters, we are now thinking of claiming 1M for
both the I/O and memory BARs to force them into 'upper memory' and 
prevent any possibility of a conflict with an ISA
device. We have confirmed the BIOS in question now puts the memory 
resource in upper memory.

The questions I have are:

1. Why would any PCI add-in card want to be 'anywhere in memory' when 
it allows the possibility of a conflict with a Legacy
ISA Adapter?

2. Is there any possible problem with each card claiming 2M from the 
32G PCI pool? The maximum number of adapters
we can put in a system is 16 (using expansion chassis).

Seems like it would have been a better solution to have the bits in 
the PCI BARs mean:
	Below 1M
	Above 1M - instead of anywhere
Then, I wouldn't need to claim more memory than I'm using to force it 
above 1M and eliminate the ISA conflict possibility.

Also, the PLX 9050 we are using has a fixed resource size of 64 bytes 
for its configuration registers, so we can not 'force'
this to be in upper memory and are at the mercy of the BIOS being 
smart enough not to create a lower memory conflict.

Any feedback is appreciated.

Thanks,
Bob Huebner

Mgr. H/W Development
Attachmate Corporation
3617 131st Ave. S.E.
Bellevue, WA 98006

email: bobhu@atm.com

tel.: (206) 649-6535
fax: (206) 649-6200

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