mapping to memory space

[tlyungha@rockwellcollins.com]

Hello,

I am using a National Geode GX1 Pentium class processor chip (this device
incorporates North Bridge functionality as well)  with the National CS5530A
Companion chip (South Bridge).  The GX1 chip has a PCI interface to the
Companion chip.   I am interfacing some embedded devices (e.g. networking
chips) to the ISA bus provided by the Companion chip.

I am looking for ways to increase the efficiency of writing to the slow ISA
bus.  Please don't tell me to connect my devices to the PCI bus.  Just
assume I have good reasons for using the ISA bus.   I think that if I map
the registers associated with these embedded devices into the Pentium's IO
space, when the Pentium writes the IO location, it will wait until the
write is complete before proceeding (no write posting).   But I am
speculating that if I map these registers to the Pentium memory space
(lower 16Mbytes), the local bus to PCI bridge in the GX1 chip will post the
write and the Pentium will not have to wait for the actual completion of
the cycle.

Can anyone confirm these assumptions?

Tom Yunghans
Rockwell Collins
tlyungha@collins.rockwell.com
(909) 868-2694