On Thu, 3 Jun 2004, wrote:
> just to keep terminology correct... the 8" inch came as single
> or double density - high density entered the marketplace with
> the introduction of the IBM AT in 1985 that had 5 1/4" high density
> disk drives.
> Maybe internationally things were referred to as low and high
> density, but not to my recollection in the States or in any drive
> datasheets I have seen.
Most of that "terminology" was actually marketing HYPE.
"Single Density" never existed until AFTER "Double Density"!
(Likewise, if you search old newspaper databases, you will
find that there was NOTHING called "World War I" until AFTER
discussion started about "World War II", and there was no such
thing as a "TRS-80 Model I" (it was simply called "TRS-80")
until the model II and III were started.)
Instead, we had "FM" ("Frequency Modulated") encoding. Then
MFM ("Modified Frequency Modulation") was developed. The
MARKETING people (a group of mindless jerks who'll be first
against the wall when the revolution comes!) came up with the
apellation of "DD/"DOUBLE DENSITY". THEN they had to
differentiate the "old" system, so they renamed that
"SD"/"SINGLE DENSITY".
Some data communication engineers would argue that "Single
Density" is WRONG, since it is really "HALF density",
with one bit of data for every two flux transitions.
And "Double Density" is really only about 3/4 density.
Then, for DSDD (double sided, double density), SOME
mindless jerk marketing people (such as at Superbrain/Intertec)
who didn't have a clue about the difference between
capacity and density, decided to call that "QD"/"Quad Density"
When number of tracks was doubled, the mindless jerk
marketing people called that "QD"/"Quad Density". Except
for the mindless jerk marketing people at Superbrain/Intertec;
they had already used up the name "QD"/"Quad Density", so
they needed a bigger superlative, and called it "SD"/"Super Density"!
The mere concept that "SD" already meant "Single Density"
was lost on newcomers who don't acknowledge anything that
happened before THEY got into it (like the MICROS~1 mindless jerks
who don't understand that a "COM file" is a memory image
executable program))
But, then, when density was finally increased, "quad density"
and "super density" were already used up as names, so the
mindless jerks called it "HD"/"High Density". "HD"/"High Density"
is MFM at 500K bits per second data transfer rate on a 360
RPM drive. (Which is exactly what 8" DD was)
"Low density" has NEVER been used as a name - what
marketing person would saddle their system with THAT??
--
Grumpy Ol' Fred cisin_at_xenosoft.com
Received on Thu Jun 03 2004 - 19:03:22 BST