[parisc-linux] Some progress with WAX_EISA (Who knows about int errupts?)

[Grant Grundler]

dkennedy wrote:
> In the X86 architecture the IO space and the memory space are logically 
> separate.  They are both accessed physically on the same bus but to
> access IO space you have to execute an IO instruction.

Same thing is true for PCI. The CPU instructions to generate I/O port
or MMIO space transactions differ in the details.

> So, why have two separate spaces?  Some of the reasons are:
> - to be different from Motorola
> - to provide a mechanism to add delays for IO while still keeping
>   memory fast (relatively speaking).

- have more address space for RAM
  (ie not used for I/O space; think 16-bit)

> Why do we care about ISA?  Well, EISA was designed to support both ISA
> and EISA cards (in the same slot) so theoretically someone could want
> to put an ISA card into a PA-RISC box.

I'm not sure we can support ISA devices on parisc.
I thought HPUX does not. Anyone know?

> Does any of the above ramblings actually help?

I've learned a few things I didn't know before.
Not sure it helped with the current discussion.

thanks,
grant

Grant Grundler
parisc-linux {PCI|IOMMU|SMP} hacker
+1.408.447.7253