12 Aug
2026
12 Aug
'26
7:35 p.m.
The BIOS and DOS and the 5150/5160 disk controller board could handle four
drives. The 3rd and 4th were handled by a DC37 connector on the back, so
putting those drives inside required a somewhat special cable.
Also set the DIPswitches. Starting with DOS 3.20, DRVPARM and/or
DRIVER.SYS let you fill DOS in on what kind of drives they were.
Rather than "dual floppy", my last XT had an ST225, one SA455 drives, one
SA465, and an SA350, and a switchable cable pigtail for connecting up a 5th
external floppy. (such as 100tpi Micropolis)
My last AT was not all in the case: slightly non-standard but almost the
same FDC board, two ST4096, one SA475, one SA455, an SA350, and a TM848
8", A COPYII-PC Option board, and an AMDEK 1280 display, (1280x800/ 50
text characters per line) and a CGA, and a controller for CX Canon laser
engine that simulated Postscript, HP PCL, and Cordata. Many of my floppy
cables had an extra switch to temporarily mask off index. I jumpered one
of my 455s to reverse write enable/protect Open notch is protected,
covered notch is writeable. (That's how software distribution can be
done on no-notch disks)
--
Grumpy Ol' Fred cisin(a)xenosoft.com
On Wed, 12 Aug 2026, Scott Baker via cctalk wrote:
For me the difference comes down to whether you have a
hard drive or a
dual-floppy.
The 5150 was the first 'business class" computer that I recall using. Two
floppy drives. The lack of the HDD leads to a particular workflow and
places limits on the software that you can run. I remember lots of disk
swapping. I also remember the built in ROM Basic, and playing with that
occasionally when there was no disk in the drive. This provided a nice
bridge from my prior computer, a Coco-2, which of course came with BASIC in
ROM. As far as the cassette port, I never used that and I assume few people
ever did. The card slots are limited, but that's part of the fun, adding in
something like a Six Pack Plus. My first experience was with with MDA and a
monochrome monitor. CGA and Hercules were something I only read about in PC
Magazine.
Of course, these computers were meant to be upgraded, and often were.
Adding the expansion chassis is a perfectly reasonable period accurate
thing to have done. There were even 80286 upgrade boards that replaced the
main CPU. So you really can justify almost any configuration that you can
build. There is no wrong answer.
After the 5150 my next experience was a Tandy 1000. Constrained on slots,
but with better graphics, better sound out of the box. This was where I had
my first HDD, some clunky external thing with a ribbon cable.
Scott