Hacker News Reader

Comment by crest | Hacker News Reader

The 6809 had two 16 bit index registers, PC-relative addressing, and upper half of the stack and data page address was taken from special purpose registers instead of hardwired. It should be a fairly straight forward compiler target. On the other hand it was late to the game, expensive and not (much) faster than 8bit microprocessors. The 6502 very cheap, fast enough when it came out, but a really annoying compiler target.

View on HN

I had a TRS-80 Color Computer when I was kid which had one major drawback: it could only display 32 characters across the screen compared to 40 characters for the Apple ][, C64 and most others at the time.

The Coco could run an operating system called OS-9 which was Unix-influenced and came with a good C compiler and also a bytecode interpreted structure basic called BASIC09.

I know C compilers were really popular among CP/M users running the Z-80 and 8080 chips and also on the IBM PC which had a segmentation system to reach beyond 64k that I thought felt really elegant in assembly language but was awkward for compilers.

Where OS-9 had all the above beat was that it was a real multitasking OS and I had two terminals plugged into my coco in addition to the TV console and could use it like a minicomputer.

When I switched to an IBM PC AT compatible my favorite programming language was Turbo Pascal which adds everything missing from Pascal to do systems programming. I switched to C when I went to college because that was supported on the the various UNIX workstations they had.

The 6809 was nice, but I think the CoCo otherwise was crap. Aside from the 32 column display and awful color scheme, the built-in serial port was bit-banged. This meant that floppy drive and serial access could not happen at the same time. This is very relevant when trying to use OS-9.

There was an external serial port as an option, but there was only one slot. So you also had to buy a slot expander (a Multi-Pak).

I had the multi pak and the external uart. The entry level price of the coco was low but I think I got most of the peripherals available for it, particularly the disks were crazy expensive. Adding it all up I must have spent more than I spent on the AT clone that replaced it ($1200)

In most ways the C-64 was a great machine but boy was the disk drive slow.

Perfect system == 6809 + SIO from the Atari800 + C64 SID + IBM PC keyboard + C64 VIC or maybe V9938.

That would be fun!

I would add the MMU from the CoCo 3, so one can bank in lots of RAM with only minor league fuss.

Note that hardware flow control makes the bit banger a lot more reliable than it would be otherwise.

I had the bit banger connected to a compact printing terminal from DEC that ran at 300 baud and had an acoustic coupler so you could log into 300 baud services with nothing but the terminal. There was not a lot of risk that this device would overflow your buffers.

Reply on news.ycombinator.com