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>>>>> "Bill" == Bill Studenmund <wrstuden@nas.nasa.gov> writes:
    Bill> On Mon, 1 Nov 1999 mcr@solidum.com wrote:

    >> Does anyone know much about how the 64 bit host bridges deals with
    >> running 32-bit operating systems with 64 bit PCI buses? Does the PIII have
    >> 64-bit address modes? Should NetBSD running on such a system be considered to
    >> be a completely different kernel architecture a la sparc vs sparc64?

    Bill> There's a difference between a 64-bit address space in PCI and a 64-bit
    Bill> data path. I don't think that the PIII has 64-bit address modes (the name
    Bill> ia32 says a lot :-) . As long as it's using a 32-but address space,

  Yes, I have since learned this. We will be getting a Micron 64bit/66Mhz
motherboard.  It has a PII on it. I don't know if/how it can make 64 bit
access, perhaps some hacks in the bridge.

    Bill> OS's are fine. The 64-bit data path will just speed up i/o.

    >> Should we consider buying Alpha or Sparc PCI motherboards instead of
    >> Pentium if we want 64 bit PCI buses?  We are building some peripherals that
    >> would like to have 2^31 blocks of PCI addresses, as well as the bandwidth of
    >> 64-bit PCI.

    Bill> If you really need 2^31 byte blocks of PCI addresses, you need a bigger
    Bill> processer architecture. I think either alpha or sparc64 would work, but
    Bill> alpha is a bit more mature. Any NetBSD port should be able to handle the
    Bill> bandwith advantage of 64-bit PCI, though.

  We need the bandwidth, yes.
  Fortunately, the 2^31 block is not required to accessible to the host
processor, just to the network adapters, except for debugging. We have
decided to permit use of a 2^26 block for debugging purposes... 

   :!mcr!:            |  Solidum Systems Corporation, http://www.solidum.com
   Michael Richardson |For a better connected world,where data flows faster<tm>
 Personal: http://www.sandelman.ottawa.on.ca/People/Michael_Richardson/Bio.html
	mailto:mcr@sandelman.ottawa.on.ca	mailto:mcr@solidum.com



 


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