[Coco] Emulating a 1980 4K CoCo on PC

[Allen Huffman]

> On Dec 31, 2014, at 4:50 PM, computerdoc at sc.rr.com wrote:
> In the '81 to '83 time frame the Coco 1 with 64K was about $200 which was when I got in on the Coco journey myself.  Although I started with Color Basic v? in my Coco 1, I had 64K so I never experienced all the limitations a 4K Coco would pose.

I got mine for $300, via a Radio Shack salesman who used his discount and did the 64K upgrade himself for me :) I didn't find out until a year or more later that it wasn't wired to access the top 32K, and I recall ordering some PAL chip or something from Rainbow that you plugged in, and it had a wire than then ran somewhere else. But hey, $300!

My first computer, the VIC-20, was 4K (3584 bytes free) and I ran out of memory just trying to draw a Pac-Man maze with print statements ;-) I got better at programming after my first few days with that book, though.

>  I did know what it was like to use the all popular unreliable Cassette Recorder for Basic Program storage.  I spent hours at a time working hard to make sure my programs stored correctly many times by recording them more than once.  Did anyone else do that too?  

Totally. CSAVE it multiple times just to be sure. But I never had a real computer tape player, so I always battled auto-level recording and stuff. I hope the $$$ ones were better.

> I have also had to restart writing my Basic program for the contest several times as it seems that XRoar exits quite abruptly if you press <CTRL>-C with no prompt for "Are you sure?"!  It is beginning to get a bit aggravating since I have Asperger's Syndrome, ADD, Bipolar Disorder and OCD!  ARGH!

Another gotcha is with how disk images are handled. By default, they load and are read only. There is an option to allow writing, but when you exit the changes are tossed (perfect for protecting disks). THere is a second option to allow it to actually write back to the disk file -- and then it just does that when you cleanly exit.

Learning the cassette stuff -- specifying input tape and output tape -- turned out to work better (and is all we'd have in 1980 anyway).

However, I have since learned that you just do File->Load and point it to a .cas file or a .dsk file and boom, it's mounted. (Still need to toggle the write options, which you can do with a simple control plus number command for each drive number.) Once I learned that it was real simple. But a curve of learning, indeed.

> anything but dull.  Now that I have proofread this email, poking the top-of-ram may not work.  If not, I may have to modify the Color Basic code to only have 4K of ram.  I'll let you guys know how this goes.

It was mentioned a few times earlier just to do a CLEAR 200,4096 so you reserve memory away from BASIC and that does basically the same thing. Easier than hacking ROMs :)

> I'm on vacation right now, so I won't be able to test all this out until I get back home this Saturday.  If any of you are in the Myrtle Beach Area or close by, I'd like to meet you.  Take care my friends.


It is 1 degrees F in Iowa, have fun...
		-- A