Jr. Dragons?

From: A.R. Duell <ard12_at_eng.cam.ac.uk>
Date: Mon Jun 23 19:14:27 1997

> Due to massive amounts of caffeine & sleep deprivation, e.tedeschi said:
> [snip]
> >I have got plenty of Dragons 32 or 64 for sale/trade/swap if you want
> >them. I need an IBM Junior and an Apple II.
> First, I have a question: Was there much difference between the Dragon 32
> and the Dragon 64, or is that just a designation of how much memory it had?

There is a little more difference than the ammount of memory - I think the
'64 had a built-in serial port (using either a 6850 or a 6551 - I forget
which) which the '32 didn't have.

As I'm sure most of the people on the list know, the Dragon is very
similar to the Tandy CoCo - both were based on the same Motorola
Application Note. The main difference is the printer port - in the basic
design there were 3 I/O lines left over once the ones needed for the
keyboard and video had been allocated. Tandy used them to make a
bit-banged serial port (TxD, RxD, CD), while Dragon used them as the
Strobe, Busy and Ack lines for a Centronics port. The data lines for said
port were the same 8 lines that were used for keyboard scanning - since
the printer would only listen when the strobe line was asserted, and the
keyboard was entirely software controlled, there was no conflict here.

> Also, I have 1 1/2 IBM-PC Jr.'s sitting in my basement collecting dust.
> They used to be complete, non-working machines (one with a "sidecar" I
> believe it's called) whereas I did get one "almost working" with spares for
> the second.

I think I mentioned this before, but I bought a PC-jr for \pounds 10.00
(about $15) at a radio rally earlier this year - the basic machine with IR
keyboard, printer 'sidecar', floppy drive and 64K RAM upgrade.

I was pleasantly suprised when IBM could still supply the TechRef (about
\pounds 50.00). I was even more pleasantly suprised when it arrived - it's
a very complete manual - schematics for everything apart from the keyboard
and floppy drive (but the latter is in the O&A Techref), BIOS source,
keyboard protocol, etc. If you are serious about restoring these machines
you should try to get it.

> Roger "Merch" Merchberger

The gates in my computer are AND,OR and NOT, not Bill
Received on Mon Jun 23 1997 - 19:14:27 BST

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