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From: brown@nicmad.UUCP (Mr. Video)
Newsgroups: comp.sys.ibm.pc
Subject: Re: problems with Hercules compatible card
Message-ID: <1447@nicmad.UUCP>
Date: Thu, 22-Jan-87 11:52:48 EST
Article-I.D.: nicmad.1447
Posted: Thu Jan 22 11:52:48 1987
Date-Received: Fri, 23-Jan-87 06:57:58 EST
References: <8701200750.AA26234@ucbvax.Berkeley.EDU> <1442@nicmad.UUCP> <1549@cit-vax.Caltech.Edu>
Reply-To: brown@nicmad.UUCP (Mr. Video)
Distribution: na
Organization: Nicolet Instrument Corp. Madison WI
Lines: 65

In article <1549@cit-vax.Caltech.Edu> tim@tomcat.UUCP (Tim Kay) writes:
>Organization : California Institute of Technology
>Keywords: 
>From: tim@tomcat.Caltech.Edu (Tim Kay)
>Path: tomcat!tim
>
>In article <1442@nicmad.UUCP> brown@nicmad.UUCP (Mr. Video) writes:
>>The Hercules card and the CGA card can exist together only if the Hercules
>>card is NEVER used in graphics mode.  The graphics address of the Hercules
>>card end up in the CGA addresssing area.  The program that is run to put
>>the Hercules card into mono mode only is HGC HALF.
>>
>>You MUST remove the CGA card before Hercules graphics mode is used.
>
>I believe this isn't right.  A screen full of Hercules graphics requires
>720x348/8 = about 32K bytes of memory.  The card comes with 64K bytes or
>TWO pages of graphics memory.  A program can double buffer; there is a
>control bit that determines which page is displayed.  The first page
>starts at 0xb0000, while the second starts at 0xb8000.  The latter address
>also happens to be the address of the CGA.  If you have a CGA, you use
>the HGC HALF command to disable the second page of memory.  You can still
>do graphics, just no double buffering.  I don't know how many programs use
>that second page of memory.  If yours doesn't, and you don't have a CGA,
>you could use the memory as a small ram disk.

OK, here is what Hercules says in their manual for the card:

Getting Started

2. Make sure that there is not an IBM Monochrome Display/Printer Adapter,
   IBM Color Graphics Adapter, or any other video board in the system.
   (For the exceptions to this rule, read the section "The Graphics
   Card's Software Switch" in this manual.)

The Graphics Card's "Software Switch"

A	Selecting A Configuration

	1. The FULL configuration is the normal operating configuration
	   of the Hercules Graphics Card and is required by Lotus 1-2-3
	   (Version 1A [my note: and 2.00+]).  FULL allows unrestricted
	   access to the 64K of Hercules card memory.  The IBM color card
	   may never physically be in your system when you are in FULL,
	   although the Hercules Color Card may be.

	2. The HALF configuration allows an IBM color card to remain in
	   the system at the same time as the Hercules Graphics Card.
	   HALF limits access to the first 32K of Hercules card memory.
	   Certain programs that use graphics, like Microsoft Word, may
	   be run in HALF.

So, I was part right and part wrong.  But, the general drift of the whole
thing is that having the CGA card installed can cause trouble.  If you
don't know what the program is going to do and it puts it into FULL mode
on its own, then the CGA can't be in the machine.  Around here we use the
rule that a Hercules card and the CGA card are NOT installed in the same
machine at the same time.  That way we don't have to worry about program
conflicts.
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