27 Apr
2017
27 Apr
'17
7:34 p.m.
On Thu, Apr 27, 2017 at 4:43 PM, Fred Cisin via cctalk
<cctalk at classiccmp.org> wrote:
On Thu, 27 Apr 2017, Ethan Dicks via cctalk wrote:
Ah. I had forgotten that detail. I only ever worked machines with
double-sided drives.
It's not impossible to find another TM-100-1 or replace it with a
TM-100-2
Actually, the IBM 5150 PC originally (August 1981) mostly came with TM100-1.
It wasn't until about nine months later, when IBM released PC-DOS 1.10 (May,
1982, which supported double sided drives) that they added TM100-2
availability. Why not use the TM100-2? It will work for any of the
single sided use, and
some versions of the operating systems supported double sided drives.
(On the Tandy version of LDOS, double sided support was undocumented,
because Tandy didn't sell a double sided drive, until the model 4D?)
I know it will work.
Remember that the PC uses all drives jumpered as if
they were :1/DS1/B:
Right. I well remember how to jumper drive selects.
Radio Shack used an "unused" pin of the
interface for drive :3/DS3/D:,
Unfortunately, that was the pin that was "reserved" for side select!
That poses a problem for model 1 (with four drives on one cable), but not
for III, 4, nor 4P
Yes. I was reading about that the other day. I don't have any
4-drive units, just multiple dual-drive units.
If you have a model 1 drive that has the modification
for drive select using
the side select signal, don't use it if you use any double sided drives in
the machine, or clip that wire on the drive.
Good to keep in mind. I borrowed a half-height "Bachelor" FD-104 from
a Model 1 for drive/controller testing. I cannot find docs for it,
and barely a mention, even in TheRef. There is one jumper block by
the 34-pin edge connector - marked D.S. / 0 / (1) / 2 / 3 / MX. (the
'1' is damaged/missing because of a PCB via). It seems the first
jumper is likely to be single/double-sided (there are 2 heads), then 4
drive selects, then the MX one-drive-only-select jumper.
You can use "half-height" drives in a model
3 or 4.
Yes but at the moment, I only have one half-height 40-track drive,
that Bachelor FD-104. My only loose drives are 80-track HD units.
-ethan