origins of IBM 3740 diskette format

[Tom Jennings]

> From: "Tom Jennings" <tomj at wps.com>
>> 8" floppy:
>> [...expletives deleted...]
>> Isn't there some standard unit of IBM cards ("a box") that's 2000
>> cards? My friend David says this is the reason for the format.

On Thu, 24 Feb 2005, Nico de Jong wrote:

> were only 73 useable tracks, as the last ones were reserved by ERMAP =
> reallocations of defective tracks. Track 0 was used for VOL and HDR labels.
> The ERMAP was located at sector 5, IIRC.

I vaguely remember such things, from the descriptions of early
floppy format docs. It's easy to forget that such things (eg. bad
block mapping) were done "in hardware".

> The way I see it, it is rubbish. Unless my brain has turned to jelly, there

What kind of jelly? Or do you mean jam? Preserves? Marmalade?