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Address Mapping



Dear PCIers,

we build a Pentium embedded system with the system (memory) address mapped 
1:1 to the pci address space. However the CPU can access the PCI Bus only 
within a 128 MB window in the third giga byte address range. We will be 
using peripherial controllers via PCI. All controllers that we have seen so 
far can map their registers anywhere in the 32 bit address space - so far 
so good. However the PCI Spec. defines a BAR type bit(2:1)=01 where the 
address has to be located below 1 MB.

Which devices use this type of BAR? Can controllers with this type of BAR 
be relevant in an embedded system (without PC operating system)?

Are there any systems which use different address mapping schemes that 1:1 
(System address:PCI address)? 

Any comments appreciated,
Pavel Peleska      Tel:   ++49-89-722-41253
Siemens AG         Fax:   ++49-89-722-28502
SN EBG1            Email: Pavel.Peleska@mch.scn.de
Hofmannstr. 51
81359 Munich
Germany
>tb