CD-ROM from SCO unlikely

Tim Shoppa shoppa at
Sat Feb 28 16:07:21 AEST 1998

> > Incidentally, a couple of weeks ago I made a nice bootable Iomega ZIP
> > cartridge with the current 2.11 generic kernel and everything in /usr.  It all
> > barely fits in the 100 Mbytes (well, 3*65536*512 bytes) available, and
> 	How "speedy" is a ZIP drive?

On my Andromeda SCDC, the effective transfer rate to the Q-bus is just
under a megabyte per second.  In other words: damn fast.  (Fast
7200 RPM SCSI-II hard drives will get 1.5-2 Mbyte second).  Booting
from ZIP is far, far faster than booting from a RD54.  I posted some
benchmarks to vmsnet.pdp-11 two months or so ago.

>  I keep threatening to get a JAZ drive
> 	for my 11 - they're nice.  I don't like the DB25 style of cable
> 	that the normal external ZIP drive uses so I'd have to find one of the
> 	rare internal ZIP drives and stuff it into a traditional shoebox.

That aren't all that rare.  You just have to go someplace other than
Fry's, that's all :-).

> > -11's with SCSI host adapters than the traditional tape distribution.
> 	Tape's good for backups though, so when I don't feel like putting up
> 	with the racket of the 9-track I just cable up the 4mm drive to
> 	the 11/73.  Alas, the QIC style of drives don't work, at least not
> 	with the Emulex UC08.  For a brief moment the Seagate Tapestore 8000
> 	appeared to work but then the whole system/controller hung (I suspect
> 	the UC08 doesn't know how to deal with more modern tape drives).  
> 	The older QIC (Wangtek-5150ES) doesn't work at all - the UC08 barfs
> 	at drives that don't do variable record mode.  Do the CMD adaptors
> 	do any better with "PC" style SCSI tape devices?

The problem is that most QIC devices are commonly operated in fixed-size-
block mode, something that TMSCP doesn't really grok well unless its
hidden under a layer that hides this and allows for variable-sized
"virtual" blocks.  (Your TK25 takes care of all of this for you

> > have - the CMD CQD440, the Emulex UC08, and the Andromeda SCDC - bootable
> > CD-ROM distributions are entirely possible.  I'm not sure if 2.11BSD will
> 	Uh, 2.11 doesn't know how to deal with 2048 byte sectors or the 
> 	ISO9660 filesystem.

That's OK.  The MSCP controllers make each 2048 byte sector look like
4 512-byte blocks.  And you don't need to lay down a ISO9660 filesystem;
if you throw away the idiotic software that comes with the PC-clone
CD-ROM writers, you can put any filesystem you like down.  I've
built bootable RT-11 CD-ROM's this way.

> > boot from a read-only device - Steven, have you tried this? 
> 	It'll panic.  For a couple reasons:  pipes are implemented via
> 	the filesystem rather than sockets so anything involving pipes
> 	needs a rw filesystem.  And a swap area is needed.  If there's
> 	memory available there won't be any actual swapping going on but
> 	argument gathering, etc during an 'exec' can use a small amount of
> 	swap space.  It might be possible to use a 'ram' disk

RT-11 also wants a writable swap file, and this is indeed provided by
using a RAM disk (i.e. VM:).

> but it's not
> 	clear to me it'd be worth the trouble.

It depends on how convenient you find installation from CD-ROM :-).  I find
the bootable ZIP disk very convenient for "recovery media", and they're
a whole lot easier to fit in my shirt pocket than a RL02 cart!

Tim. (shoppa at

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