2K blocksize for tapes

[utzoo!decvax!ucbvax!unix-wizards]

>From Hal.Cornell at UDel Tue Nov 10 02:21:08 1981
The 18-2048 byte blocksize limit for 9 track 1600bpi tapes comes
from the ANSI standard for tapes and tape drives.  Any tape drive
that claims to read ANSI standard tapes must be able to read tapes
with block sizes in that range.

Of course, most tape drives can do a lot better.  The de facto
limit is probably 32K, since most IBM (and therefore many other)
operating systems support blocks no larger than that.  However,
there are cheapo tape drives that can't do much better than 2K.

If you want to write really portable tapes that can almost certainly
be read on any computer with a tape drive, I suggest the following
format, which I've used successfully for several years:

		9 track, 1600 bpi
		Fixed-length 80 byte records
		2000 bytes (25 records) per block
		EBCDIC character set

i.e., IBM punch cards.  You may think this is an unpleasant format
(I agree), but it CAN be read by any system and translated to the
local character set, and the trailing blanks can be removed.

                            Hal Perkins
                            (hal.cornell @ udel)