Path: utzoo!mnetor!uunet!husc6!hao!oddjob!gargoyle!ihnp4!homxb!homxc!rps
From: rps@homxc.UUCP (R.SHARPLES)
Newsgroups: comp.sys.att
Subject: Re: 6300 graphics and EGA cards
Message-ID: <2870@homxc.UUCP>
Date: 20 Jan 88 13:12:53 GMT
References: <1037@bakerst.UUCP> <9300048@bradley> <835@ur-tut.UUCP>
Organization: AT&T Bell Laboratories, Holmdel
Lines: 57
Summary: VDC750 suitability with 6300

In article <835@ur-tut.UUCP>, aptr@ur-tut.UUCP (The Wumpus) writes:
> 
> In article <9300048@bradley> ninja@bradley.UUCP writes:
> >
> >> There are two cards that are being offered for the new machines.
> >> They are the VDC400 and the VDC750.
> >
> >Will they run in older 6300's as add ons ?
> 
> As far as the info AT&T has released, The Answer is Yes.  The
> installation of the card requires the disabling of the Indiginous
> Display card, but so does installation of an EGA card.

	The new card is essentially a multifrequency graphics card
	that supports CGA, EGA and AT&T's 640 x 400 modes.  Installing
	it in a 6300 is just as problematic as installing any other
	EGA card - you still have the 16bit word order problem (when
	transmitting a 16 graphics instruction to the card on the 8 
	bit bus, it must be sent as two 8 bit words.  Problem is
	which to send first?  We send the 8 high bits then the 8
	low bits, IBM sends the the low bits then the high bits.  For
	some reason, fixing this on the 6300 was "not possible".  
	The 6300 Plus uses the same word order as the IBM standard.)

	I have been told by someone at (the old) IS that "The VDC750 
	will not work in the PC6300 reliably. This is not a problem 
	with the VDC750 but with the BUS on the PC6300. It would 
	take a major redesign of the PC6300 to support an EGA type board"
	What "reliably" means it the usual problems: EGA works on some
	software but not others (Microsoft products are particularly
	troublesome).
> 
> >Unfortunately, if you've already sunk $500 or more dollars into an
> >AT&T color monitor, your only alternative is the DEB.
> 
> The new card allow the use of the old monitor you have for EGA. The
> sweep frequency of the monitor is fast enough to handle EGA with no
> problem because it can already handle DEB.

	I don't think this is true.  I was told you need the 319 monitor
	for EGA with the VDC750.  The 318 monitor is a fixed frequency 
	(25Khz) 400 line monitor.  You need a lower frequency (21.8Khz) 
	to display EGA.  The 319 can drop to this lower frequency, 
	the 318 can't.  Essentially, the 319 is a multisynch.  While I 
	have not seen this carved in stone anywhere, I have surmised it 
	from what several people have told me.  (If I'm wrong, I imagine
	someone in the know will tell me.)


Russ Sharples
homxc!rps

NOTE:

The above in NO WAY reflects the opinions of AT&T.
These opinions are my own and the results of un-scientific and 
highly irregular analysis methods.