Path: utzoo!utgpu!watmath!watserv1!watcgl!electro!ignac
From: ignac@electro.UUCP (Ignac Kolenko)
Newsgroups: comp.sys.atari.st
Subject: tos 1.4 problem?
Summary: mega addressing space
Message-ID: <1214@electro.UUCP>
Date: 28 Nov 89 21:36:18 GMT
Reply-To: ignac@electro.UUCP (Ignac Kolenko)
Organization: Electrohome Ltd., Kitchener, ON
Lines: 51


over the last couple of weeks, we've developed (for internal use only,
unfortunately) a co-processor board for the atari mega st which will
communicate to the electrohome JAZZ digital video effects processor.
this allows the atari to talk to the processor to tell it to do things
like video zooms, rotations, and special effects like checkerboard wipes,
etc. 

anyways, now that the board is working, i've begun to write some software
and i've come across a peculiar problem. we have 128K of RAM mapped in
at $C00000 to $C1FFFF. (these are addresses that the developer docs
say are reserved for mega expansion boards). we have tos 1.4 installed
in our system.

in my software, i wanted to be able to the following:

	wHandle = Fcreate ("image.bin", 0);
	if (wHandle >= 0)
		{
		Fwrite (wHandle, 0x20000L, (char *)0xC00000L);
		Fclose (wHandle);
		}

and the converse when restoring the data back into that addresses space.

now, what happened when this was run was that the computer locked up. the
hard disk light stayed on solid (but no writing was being done).
if the address of the buffer is changed to something in main memory,
there are no problems.

is this a problem with the atari DMA? is there anything special that needs
to be designed into RAM on a mega expansion board to allow DMA to occur?
does the DMA chip croak if you attempt to do an Fread/Fwrite outside of
main memory (i've also noticed that trying to Fwrite ROM writes out complete
garbage)?

anyone else noticed these problems???

an answer on this soon would be appreciated. (who's the hardware guru
at atari??)

also, is it possible to order replacement blitters??? our's is not behaving
properly anymore (bus errors when certain blitter locations are accessed,
but everything works fine when the blitter is turned off in the desktop.inf
file)

-- 
=====Ignac A. Kolenko (The Ig)           watmath!watcgl!electro!ignac=====
     co-author of QuickST, and the entire line of Quick Shareware!!!!
       "I don't care if I don't win, 'cause I don't care if I fail"
             from 'Youth Of Today' by SUBURBAN DISTORTION