[Coco] Coco 3s with > 512K RAM

[Gene Heskett]

On Wednesday, February 18, 2015 11:09:35 PM Tony Cappellini wrote:
> I seem to remember a few memory mods in the MB range.
> I'm curious how you put that memory to use.
> 
> Does Nitros9 support in-memory ram disks (as opposed to the cartridges,
> like the Disto Ramdisk)?
> 
> How do you use memory about 512k in your Coco?

I assume you mean above, in which case yes.

See the mr0.dd and mram.dr in the built repo. I wrote that to use up to 
about 1.7 megabytes of my 2 meg disto kit that is in my main machine as a 
ramdisk. If those are in your bootfile, then a simple "dir /r0" will pause 
for 100 milliseconds while it formats it at whatever size you have it set 
for, and will then show you an empty directory, faster that you can get a 
dir listing off a floppy. Compatible in every way with the os9 filesystem, 
when you are finished using it for scratchpad to build a large C program, 
a simple deiniz /r0 returns every single byte it used to the system memory 
pool.

The descriptor is used by the driver in a very simplified way, the size is 
controlled by the "dmode /r0 cyl=xx" variable, a hex number, and each 
increment in the number means it will use another 8192 byte normal block 
gime mapped into its view and reserved for its use.  With a 2 meg kit, 
cyl=1A will give you 1.7 megs worth of ramdisk.  Slightly faster that the 
equ size of surface on a hard drive. The major diff is virtually zero seek 
& settle time. A seek is maybe 40 microseconds, and needs no settling 
time.

Cheers, Gene Heskett
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