Path: utzoo!utgpu!water!watmath!clyde!cbosgd!mandrill!neoucom!wtm
From: wtm@neoucom.UUCP (Bill Mayhew)
Newsgroups: comp.sys.att
Subject: Re: 6300 graphics and EGA cards
Summary: STB Multires does not do all modes of EGA on the PC6300
Message-ID: <956@neoucom.UUCP>
Date: 19 Jan 88 15:27:23 GMT
References: <1037@bakerst.UUCP> <9300048@bradley> <888@cblpe.ATT.COM>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 30


I have the STB Multires in my PC6300.  It is only a partial
solution.  Programs that are well behaved and access the EGA
functions of the board through BIOS calls work.  GEM and Graph In
The Box are examples of well behaved programs that work completely
correctly in EGA mode.  GEM is even pretty fast.

Microsoft Windows in 16color mode and Rix Softworks EGA Paint 2005
are examples of programs that fail.  Both cause total failure
requiring a cold boot to recover.  Interestingly, Windows does work
in monochrome EGA mode (which isn't as good as the 6300 indboard).

The failures of certain programs on EGA in the PC6300 are likely
due to sloppy programming practices using 16 bit OUT instructions
to directly access registers on the EGA card.  On the PC6300 there
is an unfortunate "bug" that sends the two bytes of a 16 bit OUT
to the buss connectors in the opposite order of that chosen for the
IBM PC/AT.  The "bug" is not really an error since the AT&T PC6300
actually antedates the PC/AT.  At the time the PC6300 hit the
streets, there was no defacto IBM standard for doing 16 bit I/O.

The ROM BIOS 1.43 release included a new PAL-90 decoder chip that was
supposed to "cure" the reversed order of the bytes.  Unfortunately
the problem was not really cured by the new PAL.  Oh well.

So...  The STB mulitres is indeed electrically compatible with the
400 line, 25KHz scan rate of the AT&T color monitor, but it still
doesn't always work.

--Bill