Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!ucsd!nosc!humu!uhccux!aloha1!islenet!richard
From: richard@islenet.UUCP (Richard Foulk)
Newsgroups: comp.sys.att
Subject: Re: 3b1 floppy tape project (still on back burner)
Message-ID: <3906@islenet.UUCP>
Date: 7 Mar 88 05:14:40 GMT
References: <1035@neoucom.UUCP>
Reply-To: richard@islenet.UUCP (Richard Foulk)
Organization: Islenet Inc.,  Honolulu
Lines: 33

> software drives for various systems.  One limitation he pointed out
> is that with current generation floppytape drives are not capable
> of operating in an interrupt driven mode.  Basically, the CPU has
> to busy wait for the drive to finish a given operation.  In 4 to 6
> months, drives will be available that can generate interrupts when
> a tape operation has completed.  Capacities up to 80 megs will be
> available that can still fit into a 1/2 height 5-1/4 cutout.

Judging by the way that it works I'd guess that the floppy on the 3b1
is non-interruptible too.

I have a vague recollection of reading some data several years ago on
a tape drive similar to the one you mention that actually allowed
sector addressing via the floppy interface.  That is, it could radomly
access sectors.

From that I got the impression that such a drive might work on the
3b1 without writing a new device driver.  The rest of the system
could get some time in -- in between sectors, just like with the floppy.

But then maybe I'm dreaming.

> them.  Basically the trick to waking up the tape is to send it a
> sequnce of pulses on the head select and step leads.  Exactly what
> the commands are, I don't have at hand yet.

That sounds a little contrary to my vision of things.  At least
requiring a new driver.  Oh well.

Maybe it's time to disassemble the floppy driver.

-- 
Richard Foulk		...{vortex,ihnp4}!islenet!richard
Honolulu, Hawaii