[Coco] 512K AND Beyond??? How FAR Beyond???
Gene Heskett
gheskett at shentel.net
Wed Dec 27 02:29:42 EST 2017
On Wednesday 27 December 2017 00:30:32 Allen Huffman wrote:
> On Dec 26, 2017, at 11:23 PM, Joe Schutts via Coco
<coco at maltedmedia.com> wrote:
> > Another related question. If you have a 1 or 2 Meg system, is that
> > memory even accessible from Basic or does accessing it require OS-9
> > only (or NitroOS-9)??? Last question. Is it possible to access even
> > more memory (higher than 2 Meg) with a CoCo 3 and if so WHY hasn't
> > someone built (or even designed) a board and sell it here??? You
> > listening Ed??? Just kidding... Thanks Everyone...
>
> There was even an 8meg upgrade someone built.
>
> But no, stock BASIC won’t use it. Neither will OS-9. You had to have
> special patches for OS-9 and then it could. I do not know if anyone
> modified any of the BIG BASIC type programs for those upgrades, but
> OS-9ers made real good use of it.
>
> I am unaware of any software that was ever written to use it, though,
> Beyond OS-9, and even then, All it did was allow you to load more
> modules in memory at the same time, or have a larger RAM disk perhaps.
> Programs were still limited to fit within the 64K system area.
The program I wrote for a ramdisk, I called myram and which is now in the
nitros hg pull, now renamed mram I believe, could be configured to use
as much as 1.7 megs as a ramdisk. Its working size is determined by a
byte in the descriptor that can be changed with dmode
This automatically formats itself on the first access, taking a few
hundred milliseconds to do that, and when you are done with a big
compile it could deiniz'd returning every byte to the main memory pool.
I have a Disto 2 meg kit in mine. But it has not ran rsbasic in 10+ years
because its invisible to basic.
> Though, Bank switching and stuff could have been used to get around
> that. I jus don’t think anyone needed it.
os9 level 2 is essentially a bank switching system, handling memory in 8k
blocks, any 8 of which can be mapped into the processors 64k of address
space at any one time. The patches to take it from 512k to 2048k of ram
aren't terribly intrusive, mostly the change in the value of a byte in
the init module, from $3F for a 512k system to $7F for a 1 meg, and $FF
for a 2 meg system. The multitasking in the clock module also manages
the memory, and its possible to have 2 programs, each needing 56k of
memory, in use, and talking to each other at the same time but it takes
a lot of planning to pull that off.
Unfortunately, in the mad dash to break major modules down into separate
modules to handle the os, and separate subroutines to address the
hardware, it was not considered anything but good, until it was out of
system ram because each such module requires another $27 bytes for its
where is it tables so it knows where, and in what block of memory the
next subroutine it needs has been loaded into. All that extra data
cannot live outside of the processor address space, so for the last
decade, I have not been able to format a floppy disk as that needs
enough room in memory for a full track image, $6144 bytes, and about
another kilobyte of scratchpad for the format program itself. So for
about the last decade, by mb scripts have just erased what was on the
disk, including the hidden boot track, so it can build a new disk on one
that has already been formatted. It can even be done to a vdisk target
thanks to the sh.dd which can be pointed at any of the vdisks, so I can
do an mb without blinking a floppy drive led. But guess what? The vdisk
must be already formatted, and only 3 or 4 were ever formatted before
format started failing by crashing the system, stepping on memory
something else owned. So I have 2 hard drives of a gig each, but less
than a meg of formatted space to play with. That rather resembles that
famous rock and hard place scenario we're always being caught between.
I fussed about this years ago when the breakup was being done, but to no
avail. So it became ever more versatile until it was to me unusable.
Today, using bootlink, you only need one copy of the boot track, which
could be on a floppy, because you can finish the boot using any one of
the 255 vdisks of later versions of hdb-dos, to load the os9boot file
from.
So stripped versions of the os9boot file can be made and used right on
the hard drive simply by running bootlink to assign the next vdisk, and
doing a powerdown reset. So I could "fix" my formatting problem, but
about that time we had some water control work in the basement done to
the tune of $12,000, (whee, no more flooding) which made such a mess
scattering jackhammer dust over everything including the coco's, and the
coco3 will not get powered up until I can take it and all its goodies to
a high pressure air hose to clean it up. And the basement stairway is
becoming a problem for this old (83 now) mans legs.
Those golden years they talked about? Only in the toilet bowl.
But I keep plugging along, careing for the missus who broke a hip last
February, and because of her copd, isn't capable of doing for herself
any more. So I play the part of a remote control, doing the housework
that gets done, the cooking and laundry yadda yadda. Would I change
that? Nope.
Now, I hope everyone has a better new year.
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>
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