Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!wuarchive!uunet!mcsun!ukc!tcdcs!unix1.tcd.ie!dagraham
From: dagraham@unix1.tcd.ie (David Graham)
Newsgroups: comp.sys.mac.programmer
Subject: Quick and Dirty writing to screen
Summary: How to draw VERY FAST on screen
Keywords: Naughty, QuickDraw, screen memory
Message-ID: <dagraham.673539752@unix1.tcd.ie>
Date: 6 May 91 14:22:32 GMT
Sender: news@cs.tcd.ie
Organization: Trinity College, Dublin
Lines: 26
Nntp-Posting-Host: unix1

Hi there,

Can anyone tell me, is there a quick and dirty way of directly addressing
screen memory so I can write a very fast squidgy text drawer?

This isn't for anything 'proper', and I only need it to work on my IIsi.
Since the IIsi video memory is part of main memory (isn't it physical
addresses from 0 upwards?), can I bypass the PMMU and write straight into
'real' location 0, or wherever?

And is the screen memory organised , as described in IM V, in 'chunky'
format? So, in 256 colour mode, each byte will be a pixel?

All I need is the base address of the screen, how to bypass the PMMU trying
to turn my address into something sensible, and that will probably do.

Info on other Macs, and addressing NuBus video cards would also be
acceptable. Or if anyone could just tell me where to look, although I expect
this sort thing isn't documented, since Apple don't like people making
assumptions on changeable things like screen buffers and stuff.

Thanks in anticipation for any replies,

David Graham, JF Comp Sci, Trinity College, Dublin, Ireland
dagraham@unix1.tcd.ie
dagraham@vax1.tcd.ie