Hacking a Commodore PC10-III

Hallo allemaal,


Most of the time we are talking about hacking the C64, PET, CBM, 
etc. with as latest "victim" the Plus/4. To be very honest, after 
twenty years of 6502 I was a bit fed up with all the 6502 related 
stuff. And having various Commodore PC's on the shelf doing nothing 
at all, I decided to give them a bit more of attention. For 
example, I wanted to find a better replacement for onboard harddisk 
than the old 20 MB MFM I had. Indeed "had" because it just died two 
days ago. So I started to disassemble the BIOSes of the PC 10/20-
III and the PC-1

By accident I could lay my hands on a XT-IDE card:
http://n8vem-sbc.pbworks.com/w/browse/#view=ViewFolder&param=XT-IDE
I equiped it with the XTIDE universal BIOS:
http://code.google.com/p/xtideuniversalbios/ 
After some puzzling I was able to replace the original code for the 
unusable 8 bits IDE harddisk with the above one. Advantage: now I 
can solder the relative simple IO interface W/O the need for the 
onboard ROM.

I attached a 2.5 GB HD and installed MS-DOS 5. FYI: I chose the 2.5 
GB one for the simple reason it made the lessest noise of all 
harddisks I have. MS-DOS 5 supports UMB (= upper memory block), 
memory between the "famous" 640 KB limit and the maximum of 1 MB. 
Something the PC 10-III doesn't have so I added an old IBM memory 
expansion card, adding 64 KB in the 0Exxxx area. 
But this memory needs to be initialised as well. So I added the 
needed routines to the BIOS as well. 

Now I have to install my 23 years old UMB software and see if 
things work out fine. I have no doubt here as I have done this 20 
years ago as well but with an IBM AT.

Next steps: replace the 8088 with a NEC V20 and installing a 8087. 
And maybe a VGA card, less original but the original IBM CGA screen 
weights about a ton :(

If interested, all sources are free!


Next project: doing the same for my PC-1, just for fun! And then 
I'm going to pay attention to my just bought CMD hard disk, which 
is 6502 again :).


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