25 May
2020
25 May
'20
11:22 a.m.
On Mon, 2020-05-25 at 20:00 +0200, Liam Proven via cctalk wrote:
On Mon, 25 May 2020 at 05:30, Fred Cisin via cctalk
<cctalk at classiccmp.org> wrote:
IBMs came with an installable driver called, I think, IBMCACHE.SYS.
This used extended RAM (above 1MB) as a hard disk cache, without XMS
or HIMEM.SYS or any of that. I played with it and was amazed by the
results. I started enabling it by default on customers' machines.
I hadn't thought about IBMCACHE.SYS in *years*. I wrote it in its
entirety (there's even a patent that covers some of its operation). I
was in an AdTech (Advanced Technology) group at the time and was
looking at how to make disk operations faster in DOS at the time when I
came up with the idea.
There was a *huge* battle within IBM on if it should be released and in
order to do so, it was fairly well hidden.
Most
were happy but some had the habit of just turning off -- DOS didn't
really have a shutdown routine. Some, I could train to press
Ctrl-Alt-Del before turning off. Some I couldn't, so I had to disable
the disk cache.
There was a switch on config.sys statement for IBMCACHE.SYS to turn off
the write-back cache (e.g. writes would always go straight to disk).
As I recall, there was a 30 second timer for the writeback cache so
that if a disk block was "dirty" for more than 30 seconds it would get
flushed to disk.
But for those that could learn and adapt, it made DOS _much_ faster,
and on a 1MB PS/2 Model 50 or 60, it was about the only thing you
could do with the extra 386 KB of RAM before MS-DOS 5 came out.
TTFN - Guy