16 Sep
2013
16 Sep
'13
6:06 a.m.
Fred Cisin wrote:
We all know
that DEC used a SS / DS drive.
The question is whether there existed anybody who mad DS without the SS
sensors.
The original question had been about an SA800 drive, and did not mention
DEC.
[continued after minor crisis interruption, sorry about that]
I'm certainly not disputing that certain ones, presumably almost all, are
SS/DS.
But, that DOES cost a trivial amount extra. They have to add an "extra"
sensor.
There are at least three obvious analogous situations:
1) My AT 1.2M drives (a sloppy, but not very ambiguous name for it) can
also read and write 360K disks (a very sloppy but not very ambiguous name
for it).
BUT, not all can!
One of the very first "1.2M" drives that I got (an EARLY Mitsubishi 4854
with FIFTY pin interface connector!) could not reliably do "360K"
The speed was fixed at 360RPM (which is easily compensated for by a
300Kbits per second data transfer rate), and there was no provision for
alternate write current. LATER 4854 drives could do 360K just fine, and
switched to a 34 pin connector.
2) It is generally possible to do "720K" (a very sloppy, but
relatively unambiguous name for it) with a "1.2M" drive. BUT, not all.
The above drive, for example, could not.
Teac made 55F (720K), 55G (1.2M), and a 55FG (720K/1.2M) drives. Only the
55FG was explicitly intended to be able to do both. And the differenceS
betwqeen the 55G and 55FG??
3) "1.4M" (a sloppy name, but it's clear what is meant, and not as
blatently WRONG as "1.44M"(multiply 80x2x18x512!)) can "normally"
handle 3.5" "720K" (a sloppy name, but you know what is meant).
BUT, that is not NECESSARILY so. NOT ALL DO.
4) Most of thsi sort of FDC can handle 4 drives. But many are hardwired
for 2 drives, and some are hardwired for ONE drive!
It MAKES SENSE for a newer design to be compatible with the previous one,
IFF it can be easily achieved. Is "common sense" completely an oxymoron?
Some manufacturers are so frigging stingy that they would skip that easy
fundamental backwards compatability, just to save a few cents.
How could a DS 8" drive manufacturer be unwilling to spend a few cents to
be able to handle SS AND DS? I do not have an example. and that was what
I was asking.
How could a "1.4M" drive manufacturer be unwilling to spend a few cents to
be able to also handle 720K?? But they exist!
How could a "1.4M" drive manufacturer be unwilling to spend a few cents to
be able to automatically detect which disk was in the drive?? IBM in
their PS/2 series!
How could a "1.2M" drive manufacturer be unwilling to spend a few cents to
be able to handle "low density" ("360K"/"720K")?? But they
exist!
How could a "1.2M" drive manufacturer be unwilling to spend a few cents to
have both 300RPM and 360RPM for EASIER use of both "360K" and
"1.2M"??
Many early "1.2M" drives had only 360RPM; and required adding an
additional 300Kbits per second data transfer rate to the existing 250K
and 500K of the FDC, just to be able to use "300RPM" disks in the 360RPM
drive!
So, YES, there are precedents for manufacturers being so stingy as to
cripple their product, when a trivial expense would provide full
compatibility.
--
Grumpy Ol' Fred cisin at xenosoft.com
I agree that prices for hardware have been falling, but mostly
because the volume is so large. If cars were made that way,
the cost would be less than $ 100.
Jerome Fine