[abc80] abc80x emulation status in MESS

Curt Coder curtcoder at yahoo.com
Sön Aug 5 23:11:31 PDT 2012

It's the only controller I have schematics and ROMs for... 

I have a dump of the FD2 controller but no schematics.

So the 80-column cards don't have a font ROM at all?
Do they use an MC6845 or TTL logic for the display?

 From: H. Peter Anvin <hpa at zytor.com>
To: Curt Coder <curtcoder at yahoo.com> 
Cc: "abc80 at abc80.org" <abc80 at abc80.org> 
Sent: Sunday, August 5, 2012 8:52 PM
Subject: Re: [abc80]  abc80x emulation status in MESS
On 08/05/2012 09:17 AM, Curt Coder wrote:
> Hi,
> The Luxor computers should be fully operational in MESS except for the
> exceptions listed below:
> abc80
> - cassette read
> - floppy (slow controller requires Z80 RDY emulation which we don't have yet)

Any specific reason you insist on using the slow controller for ABC80?

There were so many controllers and floppy disk solutions for ABC80 (there were at least three vendors - Scandia Metric's FD series, Luxor's ABC series, and Tranfor's Datadisc series, and of these Luxor's was probably the least popular for ABC80) that I don't think anyone cared about the exact timings.

> I'm currently looking for the following to complete the emulation:
> - dumps for ABC80 peripherals (80-column cards, BASIC V1, etc)

BASIC v1 being the one that is generally known as "checksumma 11273" I believe.  The 80-column card changed only a handful of memory locations when invoked, unfortunately I only have the patch for checksum 9913 (BASIC v1.02).  Which exact patch depended on the exact 80-column card you used; there were at least three variants from I believe two different vendors, one (Gejo) which put the extra RAM at 7400h-77FFh (29696) -- early versions 7800h-7BFFh but that conflicted with the printer -- and one (MyAB's TKN80, probably the more popular) which put it at 5800h-5FFFh so that it would be contiguous (5C00h-5FFFh being a shadowed to 7C00h-7FFFh) but that caused problems with other peripherals...

The only difference between the three models as far as the BASIC ROM is concerned is the address table at address 884 decimal (0374h) which contains the start address for each of the 24 lines.  The additional changes for checksum 9913 were:

    Address        Value
    0x01d8        0x50
    0x0211        0x50
    0x024e        0x50
    0x026f        0x4f
    0x02de        0x50
    0x033c        0x50
    0x22f2        0xa0

My FPGA model mimics the later Gejo version (7400h).


-- H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

More information about the ABC80 mailing list