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SubjectRe: holes for ISA boards...
On Sat, Jun 12, 1999 at 02:17:54AM -0400, Tom Leete wrote:

> IIRC, ISA busmastering devices are able to treat the conflicting
> memory as a physical framebuffer, allowing protected mode writes
> to be mirrored in device memory. The X server or device driver has
> to know how to set this up.

Hmm... the documentation for my framebuffer doesn't mention anything
about busmastering, (and the schematics show ISA address pins wired
straight to the controller,) and my motherboard (FIC PA2013) doesn't
support a memory hole from 12-16MB. So I guess I'm out of luck...
but fortunately there's no shortage of old 486s around here. :)

[SNIP]
> I see three possible solutions to the problem, aside from (pre-1).
> "Buy a new video card", which is OT. Other suggestions are solicited.
[SNIP]

> (3) I dimly recall that the PCI bridge device was supposed to be
> able to remap the ISA bus. If true, this might be the real solution
> for most of us. Does the kernel PCI code support such a thing?
> I'm looking, but I haven't found any answers yet. PCI gurus? This
> might sidestep the deadlock and let existing drivers do the job.

This sounds like it would be the optimal solution in my case, but
unfortunately I'm just trying to hobble together something quick
& fast for prototyping and development and am short on time for
fighting with PC hardware. :) (The framebuffer will eventually
end up in a m68331-based embedded system, so all this PC hardware
wrestling isn't terribly productive for my company...)

Eventually, it would be neat to reprogram the PCI-ISA bridge to support
things like this, as well as supporting memory holes for older ISA-only
systems, and perhaps I'll revisit these options in my personal time...
:)

Anybody interested in the framebuffer hardware can find information on
it at http://www.erd.epson.com/pdf/1355/contents.html.

----
Aaron J. Grier | Frye Electronics, Tigard, OR | aaron@frye.com
"People who are more than casually interested in computers should have
at least some idea of what the underlying hardware is like. Otherwise
the programs they write will be pretty weird." -- Donald Knuth

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