Re: Mystery hardware query

[dempson@actrix.gen.nz (David Empson)]

Michael J. Mahon <mjmahon@aol.com> wrote:

> David Empson wrote:
> > One similar product I can think of is the Nestar networking system we
> > had in high school (I was there from 1981 to 1985). It had a parallel
> > network interface between the computers, with a dedicated Apple II+ file
> > server with a 20 MB hard disk (which was about two feet wide, one foot
> > high and four feet deep).
> > 
> > Around 1984 I reverse engineered the Nestar card firmware and patched it
> > to add support for ProDOS. The Apple II card only supported Pascal and
> > DOS 3.3, and there was probably some CP/M support (which I never
> > investigated).
> > 
> > The server also supported SOS, so presumably there was an Apple ///
> > version of the card. I doubt the Apple II card would have worked in an
> > Apple /// because it had I/O mapped into the $CFxx page.
> > 
> > The Nestar card was purely a network interface (and could boot the Apple
> > II).
> > 
> > The server was running a heavily patched version of Pascal, with a
> > special controller for the hard drive (from which it was able to boot).
> > There was also a dual 8 inch floppy drive, which was also gigantic.
> > 
> > The server hard drive was able to be partitioned into multiple logical
> > volumes, which were named (in a hierarchical volume file system, I
> > think) and tagged with the type of file system they contained (Pascal,
> > DOS 3.3, CP/M, SOS or various special types). Partitions could be
> > dynamially created and deleted, and they had a reasonably extensive user
> > authentication and permission system.
> > 
> > At its peak, our network included about 17 Apple IIe workstations on the
> > Nestar network.
> 
> Just out of curiosity, what data bandwidth did the network support?

It was an 8-bit parallel bus, with handshaking. Somewhat like a parallel
printer interface, with a data strobe and an acknowledge. I don't recall
details about the protocol and I'm not sure if I ever analysed its
performance in close detail.

Each sector or block was transferred over the network as a single burst,
and the average performance of the network was pretty bad with a lot of
computers tring to use it at once, probably due to the contention phase
and polling time.

Some specialised applications were able to hog the network for short
periods in order to transfer a larger amount of data. One example was
the network login screen, which loaded a fairly large amount of data
quickly.

The network card clicked the speaker every few bytes transferred,
resulting in a characteristic tone as it transferred large bursts of
data.

My recollection is that it was comparable to a 5.25" floppy, but without
the overhead of seek times, as long as the network wasn't congested.

That would make it about 20 KB per second on average, with the peak
transfer rate perhaps approaching 50 KB per second.

-- 
David Empson
dempson@actrix.gen.nz