Re: [PATCH] Intel x86-64 support merge

[davidm@mostang.com (David Mosberger-Tang)]

>>>>> On Thu, 19 Feb 2004 17:06:58 -0500, Bill Davidsen <davidsen@tmr.com> said:

  Bill> David Mosberger-Tang wrote:
  >>>>>>> On Thu, 19 Feb 2004 00:40:24 +0100, Arjan van de Ven
  >>>>>>> <arjan@fenrus.demon.nl> said:
  >>
  Arjan> On Wed, 2004-02-18 at 23:57, H. Peter Anvin wrote:
  >> >> Because they were caught by surprise and just hacked the chips
  >> >> they had in the pipeline, presumably.

  Arjan> fair enough; I hope this means the next generation has this
  Arjan> wart fixed...
  >>  I wouldn't hold my breath.  My impression was that the Intel
  >> chipset folks don't want I/O MMU because (a) Windows doesn't need
  >> it and (b) real machines use (close-to-)64-bit-capable hardware.

  Bill> Doesn't need it? Does that mean the Win64 uses bounce buffers
  Bill> for everything? Or am I totally misreading this?

Remember: I'm just the messenger here...

I have no idea what Win64 does, but obviously bounce buffering is only
an issue for devices that can't address all physical memory.  These
days, even relatively low-end machines have devices that can address
"more than enough" physical memory (I'm not sure exactly what the DMA
limit of, say, a Kenai32 e1000 card is, but it's a lot more than 4GB).

	--david