On Fri, 4 Nov 2005, Zane H. Healy wrote:

> At 4:27 PM -0500 11/4/05, Bob Supnik wrote:
> > Not for tapes
> >
> > Under Linux, access to raw disk drives just happens to work, because
> > the C-library buffered I/O used by SimH can be successfully
> > implemented on the raw drive; fread, fwrite, and fseek all work.
> >
> > But simulated tapes have a metadata record structure that real tapes
> > lack, and there's no way to express the positioning directives, which
> > are all done with fseek.
> >
> > The SimH magtape library is structured to allow for addition of
> > OS-dependent raw tape access, but no one has been interested enough to
> > do it.
> >
> > /Bob

> So, if I hook the external SCSI box for my /23+ (it's in a BA23 so the drives
> aren't internal like on the /73), I can plug in one of the HD's from my
> PDP-11's I can access them via SIMH? I've plugged them into a Linux box
> before to use 'dd' to make disk images that can then be burned to CD-R, or
> used under SIMH, but the closest I've ever come to this was trying to boot
> from one of the CD-R's a few years ago.

Yes, it should work just fine.

> BTW, KLH10 can handle both physical, and virtual tape drives, looking at it,
> might give someone ideas as to how to implement this in SIMH.

There is nothing difficult in talking to a tape, it's just that it's by
neccessity different than emulating a tape, as opposed to a disk, where
emulating and using the real thing works just the same under Unix.

So unless you explicitly write the code to deal with real tapes, it will
not work. If you simulate a disk, the same code will work straight off on
real hardware as well.

But you should know this. :-)


Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt@update.uu.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
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