3b5 tape driver question

[Darryl Baker]

In article <3794 at gatech.CSNET> hope at gatech.CSNET (Theodore Hope) writes:
>I am writing some software which will ultimately run on an AT&T 3b5 (sVr2).
>Part of this ordeal involves reading a tape written on a Big 'Ol IBM machine;
>the tape has variable-length blocks of _up_to_ 6444 bytes.
>
> * I can read it on a Vax (4.2bsd): nc = read (fd, buf, 6444)
>
> * I can't read it on an AT&T 3b20 (sVr2): the mtc documentation (documentation,
>   what documentation?) specifies that the largest possible read is 6144 bytes.
>
>
>The abovementioned 3b5 is on the other side of the world, and I'd like to
>know if anyone can tell me what the max read on the (raw) tape device is.
>Is it 6144 (6k), or 8192?

After a couple of years at the ATT UNIX System Support Center I think I
can answer these questions.

For the 3b20:
		The limit is 6k(6144) bytes using a un52 tape controller.
		The limit is much larger with a TIOP, un132, and Keystone III
		combination. (This was new when I left and I've forgotten
		the limit but it was greater than 14k). Yes, Virginia it will
		read tar tapes blocked at 20).

For the 3b5:
		The limit is 8k(8192) bytes.

-- 
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				From the sleepy terminal of
					Darryl Baker
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