expansion differences (was Re: Micro$oft Biz'droid Lusers)

From: Richard Erlacher <edick_at_idcomm.com>
Date: Sun Apr 28 10:23:38 2002

Yes, the enhancements that finally found their way into to the Model 4 were
available from third parties (with the possible exception of the display
format and speedup) for the Model I. We offered our own versions in a design
alternative done under contract to Tandy as a Model 3 design, in the very late
'70's, but it cost them $5 per unit more than the lowest-cost alternative, so
they rejected it. They paid for the work but didn't use it.

It's too bad it took them so long to realize that having two operating systems
available rather than just one would help their sales rather than hurting
them, and that a conventional display made a lot of sense, and that having the
slowest computer on the market might be hurting their competitive position.
By the time the M4 came out, most of the Z80 systems people wanted were
running in the 6-8 MHz range and cost considerably less than the M4. Tandy
management was just not able to keep pace.

----- Original Message -----
From: "Tony Duell" <ard_at_p850ug1.demon.co.uk>
To: <classiccmp_at_classiccmp.org>
Sent: Saturday, April 27, 2002 3:18 PM
Subject: Re: expansion differences (was Re: Micro$oft Biz'droid Lusers)

> > said was that the basic unit wasn't much more than a toy, since the EI and
> > disk drives didn't come out until some time after the TRS-80 became
> > The Radio Shack experience was pretty much the first one of its kind, i.e.
> > they put out what they thought met their "most likely to sell" criteria,
> > though they were pretty wrong about the concept in several respects, all
> > associated with packaging. They figure that out and fixed most of the
> > problems in the Model 3. They didn't fix all the problems, of course,
such as
> > that inane display format and the slow cpu, but, they got the packaging
> > somewhat better.
> The Model 4 did fix the display format (80*24), the CPU speed (IIRC it
> could run the CPU at 4MHz) and it even let you switch out the ROMs to
> have a 'RAM-only' memory map to run CP/M. Of course it was rather too late.
> Actaully I prefered display dimensions being nice round numbers like 16
> and 64. I could never really understand the reasoning behind 80*24
> (except that it was a 'standard').
> > > I really can't see why you claim the Apple ][ was designed as a computer
> > > and the TRS-80 (say) was not.
> > >
> > The obvious distinction is in that the Apple ][ was intended to be
> > with cards you could buy. Like the other "toy" vendors, which came along
> Err, and the CoCo (which is the TRS-80 which started this discussion --
> please don't arbitrarly move to a different machine!) was intended to be
> expanded by cartridges you could buy (like the disk controller, RS232,
> speech/sound, etc).
> > somewhat later, RS figured you should buy expansion hardware exclusively
> > them, so they didn't provide a generalized expansion interface, but,
> Eh? the CoCo expansion slot was the 6809 bus. Like the Apple slots were
> the 6502 bus. Both machines had a slot pinout, etc, that was designed for
> that machine, and both manufacturers would probably have liked it if
> you'd bought all your add-ons from them. But none-the-less both
> manufacturers did tell you the pinout and signal specs so you (or any 3rd
> party company) could make add-ons if you wanted to.
> I really can't see the difference between the CoCo and Apple ][ in this
> respect.
> > > Apart from pre-packaged business systems, very few micros came with word
> > > processing software. It was always an optional extra.
> > >
> > Yes, but if, by way of comparison, you bought an Ampro "Little Board"
> > only preceeded the CoCo by a few months (?), you had your choice of
> Sure, but none of them were free (AFAIK). Wordstar was not cheap back
> And the CoCo did have software available essentially when it came out
> (or at least _very_ shortly afterwards). And it wasn;t that expensive
> > > So, you needed to buy the Little Board, a serial terminal, at least one
> > > disk drive (I can't believe $200 included the drive), and probably a PSU
> > > and a case. And then get it all working. Fine if you knew what you were
> > > doing. Not so good if you were starting out.
> > >
> > > And presumably using Modem7 to transfer programs from 8" disks (the
> > > _only_ standard CP/M format) to the Little Board implied you had another
> > > CP/M computer with 8" drives. You know, this is starting to sound
> > >
> > Well, if you bought a new terminal, it meant an outlay by 1983 of
somewhere on
> > the order of $550. If you got one second-hand, $100 might do it. If you
> Exactly. Rather more than a CoCo.
> In other words, if you had the money there were better machines than the
> CoCo. Nobody disputes that. But I would guess that getting a Little Board
> system up and running using entirely new parts (Little Board, Terminal,
> Drives, Case, PSU, etc) would cost around $1000. The CoCo was under half
> that. Yes, by the time you'd added drives, monitor (rather than using
> your existing TV), etc to the CoCo you'd probably spent as much. But you
> could spend the money a bit at a time and have something that was useful
> along the way. And of course in the end you did have a multi-tasking
> computer with a much nicer processor than the Z80.
> > >
> > > Sorry, I have to disagree with you there. Many of my computers don't
> > > have any form of video output. The think I look for when choosing a
> > > computer is the _processor_ and _OS_.
> > >
> > I've long (very long) considered a display of fewer than 24 lines of 80
> > characters pretty useless. True, 80 column lines in pages of 24 date back
> As I said, having used many systems with less video capability than that
> for real work, I can't agree with you.
> > > Seems reasonable. But that's because the purpose of a Hi-Fi system is to
> > > produce sound with minimal distortion, and most of the distortion comes
> > > from the speakers. The purpose of a computer is not just to output
> > > It's to do processing as well.
> > >
> > True, but it's got to tell what the outcome of your processing task was.
> Which, depending on the task could be done using a row of LEDs, a 7
> segment display, a printing terminal, or....
> > > Well, if you're just starting out you have to get a lot right just to
> > > that monitor. All the bus connections correctly wired and no shorts. CPU
> > > clock running. Memory map as you (and the monitor ROM) expect it. ROM
> > > correctly programmed. I/O devices where the monitor expects them. And so
> > >
> > > None of this is impossible, or even that difficult. But for a first time
> > > project there's a lot that can go wrong, and you might well then not
> > > how to look for the problem. If you started with a CoCo (or whatever)
> > > had a base machine that would work. If your device stopped the machine
> > > from even starting up it was a fair bet you'd got a short between 2 bus
> > > lines. If it didn't repsond to the right addresses, you'd mis-designed
> > > the address decoder. And so on. It was a lot easier to get your first
> > > hardware project working that way.
> > >
> > removing the CPU and using switches to set the addresses was an easy
> > way to check whether a CPU communicated properly with an I/O decoder and
> Oh, sure... I've done that many times. That's not the point...
> When you know what you are doing, there are plenty of ways of
> fault-tracing using minimal equipment. But when you're starting out you
> probably don't have the ability to work out things like that. Having
> something to start from that you know works is a big step forward. Or at
> least it was to me.
> This was one thing that was so nice about the BBC micro. It had an 8 bit
> user port (half a 6522) and a 4 channel ADC built in. Now, we both know
> how easy it is to link up a 6522 or an ADC chip to the 6502 bus. But I
> can assue you that the fact that these interfaces were built-in on the
> Beeb enocouraged a lot of users to link up relays and simple sensors,
> etc. And to actually try some interface. They probably wouldn't have
> bothered if they'd had to wire up the interface chip themselves first.
> And they certainly wouldn't have tried making a computer from scratch.
> > I guess I consider it pretty simple because that's how I got my first
> > working. I took a memory map from an existing architecture and, because I
> Actually, I debugged my first homebrew like that as well. And used an LED
> + resistor to monitor bus signals. From the brightness of the LED I could
> estimate the mark-space ratio of the signal (and certainly spot lines
> that were always high or low).
> I am not saying it can't be done. Just that few beginners are going to do
> Another data point. Look at all the projects on the internet that connect
> to a PC printer port. Now, making an ISA card is almost trivial, and in
> some cases it's actually more work to kludge the interface onto the
> printer port than to make a special ISA card for it. But none the less,
> people prefer to just plug into an external connector on an existing
> computer.
> > > > resident ROM was handy, provided you could make it go away.
> > >
> > > You could. Look at the SAM data sheet.
> > >
> > I was hoping to avoid that ...
> I see, you (as usual) can't be bothered with facts....
> -tony
Received on Sun Apr 28 2002 - 10:23:38 BST

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