9-Track Tape Density Terminaology Query

From: Bob Shannon <bshannon_at_tiac.net>
Date: Mon May 6 22:30:43 2002

Here's my 'guesses'...

Douglas H. Quebbeman wrote:

>Should have asked this 20 years ago when everyone
>remembered (well, those of you who'd been weaned by
>that point, anyway...).
>
>200, 556, 800, 1600bpi: bpi, bits per inch. I understand this one.
>
>3200 cpi: is this characters-per-inch?
>
Yes. BPI is also the linear tape characters-per-inch. BPI really
describes one-ninth of a 9-track
or one-seventh of a 7 track (is that one-fifth of a Linc Tape?). CPI
technically described all the
tracks at once, the data and the parity (9th) track. But the numbers
are exactly the same in all cases.

>
>6250 fcpi: what, "framed" characters per inch?
>
Formatted. 6250 uses really fancy modulation methods. Rembering a
cranky old tape
controller, I beleive that there is a pre-amble servo burst at the start
of tape records and
marker characters that lowers the average tape density. The 6250 spec
in only hit inside
a record. Your milage may vary based on block size, etc.

>
>One certainly can't figure this out merely by looking
>at the capacities of the various modes...
>
Nah, you gotta look at mag tape formatter schematics and microcode!

>
>Mostly just a curiosity, nothing really hinges on this...
>
>-dq
>
Nothin' says Vintage Computer better than a mini with the switch
register blinking and 10 inch reels
of tape jumping back and forth.

Not even an Altair or Imsai can touch that. (for those of you who lack
room for CPU's that don't fit
on a chip)

Now cold-booting from 9-track mag tape, thats pure Vintage Computing
(without the nasty cuts of paper tape)!
Received on Mon May 06 2002 - 22:30:43 BST

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