[abc80] abc80x emulation status in MESS

[H. Peter Anvin]

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).

	-hpa

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