XT COMPUTERS

From: Kai Kaltenbach <kaikal_at_MICROSOFT.com>
Date: Fri Aug 8 15:07:29 1997

Hi René,

I guess that would be my specialty.

The PC memory map looks like this:

C000 - FFFF - Various open areas depending on the individual machine,
plus the BIOS
B800 - BFFF - Low resolution (CGA or EGA/VGA low res/text) video (if
present)
B000 - B7FF - Monochrome adapter (if present)
A000 - AFFF - High resolution (EGA/VGA) video (if present)
0000 - 9FFF- Base 640K

I think what you mean is you'd like to use the high resolution area from
A000-AFFF to increase base RAM size. The low resolution area is not
contiguous with base RAM so it can't be used to increase base RAM size.

The trick is, there is no RAM in this location that you can use to
increase the base memory. So, you have to put RAM there somehow (no,
video RAM won't work). There are various methods to do this.

On a 386 or above, the virtual memory management allows a 386-up memory
manager such as EMM386, QEMM386, or 386MAX to map memory into that
location.

On a 286, you could use various LIM 4.0 compliant expanded memory boards
(e.g. Intel AboveBoard Plus) or a wacky device called an ALL Charge
Card, along with special software to map memory into the location.

On an 8088, you had to use a special card, which was a very simple
device containing 64K or more of RAM, along with address selection
switches. The card would map RAM into that location, and came with
software to extend apparent DOS RAM.

Kai

> ----------
> From: SSE Technical Support
> Reply To: classiccmp_at_u.washington.edu
> Sent: Friday, August 08, 1997 12:18 AM
> To: Discussion re-collecting of classic computers
> Subject: FW: XT COMPUTERS
>
>
>
> -----Original Message-----
> From: Mr. Self Destruct [SMTP:more_at_camlaw.rutgers.edu]
> Sent: donderdag 7 augustus 1997 19:26
> To: Rene van der Meer
> Subject: Re: XT COMPUTERS
>
>
> On Wed, 6 Aug 1997, Rene van der Meer wrote:
>
> > Hi my name is René
>
> Hello.
>
> > I am looking for a program that allows me to break the 640kb and
> uses the
> > cga memory address to make 768kb I am not sure if this exists I
> belief so..
>
> I've heard of such programs, but many were machine specific and/or
> flaky.
> I'd recommend asking the fellows at the classic computer mailing list
> at:
> "classiccmp_at_u.washington.edu"
>
> > it is for a KAYPRO XL
> > my direst computer that I ever had...
> > please help me ...
> > my e-mail address is renemeer_at_xs4all.nl
> > I to like old junk
>
> Glad to hear that!
> Les
>
Received on Fri Aug 08 1997 - 15:07:29 BST