Subject: Re: DMA beyond end of isa
To: None <Chris_G_Demetriou@NIAGARA.NECTAR.CS.CMU.EDU,>
From: Andrew Cagney <>
List: tech-kern
Date: 01/05/1996 21:13:19
Excerpts from mail: 4-Jan-96 Re: DMA beyond end of isa Bill
Studenmund@loki.Sta (2776*)

> The outline of the spec is one or more PowerPC's on a PCI bus connected
> to a PCI-ISA bridge. A chip on the PCI side impliments most of the
> Mac's hardware, and chips on the ISA side do most of a PC's (such as
> soundblaster-compatable audio, COM1-COM4, LPT1, PC keyboard, etc.)
> I/O. Most of the IO will be accessable little-endianly and
> big-endianly (the video buffer in particular).

Some trivia...

The PCI-ISA bridge would more then likely be based on the 82378 which
supports dma (on the PCI side) to the full 4gb of RAM.  Do x86 PCI
machines already use this chip?

When it comes to the 64bit CHRP platforms. CHRP mandates mapping
hardware (bounce buffers in silicon) that can map DMA from a 32bit bus
into any where in a 64bit address space.  Guess generic suport for that
is also needed :-)