[Coco] How much memory

[Roger Merchberger]

On 11/28/2010 10:07 AM, Frank Swygert wrote:
> As Steve said, OS-9 was designed in the late 70s/early 80s when anything
> more than 64K was a dream for 8 bit computers. Memory was a bit
> expensive, and everything was done with text screens. Who needed even
> 64K? Only a (for the time) sophisticated OS like OS-9 could fully use
> 64K! Then graphics came along and needed more memory, programs became
> more sophisticated (and slopier coded!), memory and computer prices
> started dropping, etc.

I'd have to disagree -- I was constantly bumping up against the 64K 
barrier on my CoCo2 with OS-9 even without graphics, and 512K was a 
godsend in my CoCo3 -- being able to run TS-Edit in one window, with 
DynaCalc in a 2nd window, Rogue in a 3rd window, and still be able to 
run a 200K ramdisk was when the CoCo was finally "roomy enough" for my 
needs, and I could get a *lot* more work (or play ;-) ) done without 
constantly exiting applications to free up RAM.

When it came time for me to "join the PC revolution," I couldn't believe 
how much my productivity *slowed* on the fast hardware because I 
couldn't multitask any longer - pretty much relegating my shiny new PC 
to "nintendo" status, and specialty tasks like AutoCad; I kept the CoCo 
for "serious work." ;-)

> The real limitation for OS-9 is the system space, which is limited to
> 32K I believe... or is it 64K? Part of the problem there is it's an 8
> bit OS. I'm not familiar emnough with the internal workings of OS-9 to
> comment further.

Neither do I, but I'll comment anyway ;-)

I'm pretty sure it was 64K, but most (all?) the running OS had to be 
mapped into memory, which reduced the usable application memory to about 
32-40K. I remember trying to shoehorn OS-9 into few enough 8K (is that 
right?) blocks to try to get 48K application memory available, I think I 
was successful (barely) in Level 1, but was unsuccessful in Level 2. 
Level 2 was tough to shoehorn into 24K RAM leaving 40K application 
memory, and still leave enough pre-loaded programs to be useful on a 
floppy system. IIRC, 40K available application memory would give you 
about 23K working memory in Dynacalc, which was one of the reasons I was 
trying to eke out as much as I could.

> ---------------
> Date: Sun, 28 Nov 2010 00:52:08 -0400
> From: "RJLCyberPunk"<cyberpunk at prtc.net>
>
> I find it odd that OS9 has that limitation that all other current computer
> operating systems do not have. why have the designers of OS9 built a 2MB
> memory address limitation?

"All other current operating systems" -- Remember, when OS-9 was 
current, Microsoft recently purchased QDOS, and DR was actively selling 
CP/M... 8-bit CP/M had a 64K memory limit, DOS 1.0 was probably the 
same, or possibly 128K (remember the PC started with 16k/64k 
motherboards as well) -- when the hardware in the IBM PC came closer to 
handling a full Megabyte, DOS could only handle 640K. Once Meg+ boards 
came out, it took a *lot* of hackery to get around that 640K limit. 
TRSDOS? Same thing, until the Model 4 came out that could handle 
bank-switched 128K, etc.

Let's talk storage: IBM PC and/or DOS partition size limits: first limit 
was 32Meg, second was 128Meg, then 512Meg, then 2Gig, then 128Gig and 
now 2Tera IIRC... Those "in power" [1] bump the limit when the hardware 
is built. OS-9 *started* with a 4G limit back in '80s when the only 
thing big enough to hold it was on mainframes / supercomputers. By the 
time the hardware caught up the the limit in OS-9, the CoCo hadn't been 
marketed for 5 years or so; and even then, 4G drives *weren't* cheap.

[1] that rather makes me sound paranoid... ;-)

A 2M RAM limitation on a computer that's not _supposed_ to go beyond 
512K I don't really see as a limitation. I'm also pretty sure that 
OS9-68K doesn't have this limitation as the computers could address more 
memory, the OS would be designed around those capabilities.

OS-9 in almost every respect was really ahead of it's time!

Ah well, enough rambling... ;-)

Laterz,
"Merch"