TRS-80 Model I

Liam Busey buseyl at yahoo.com
Sun Feb 4 02:05:40 CST 2007


--- Tony Duell wrote wrote:

> > Interesting. Most people seem to say nice things
> about
> > the Apple ]['s design. I'd love to hear some
> informed
> > bashing ;) . Could you elaborate some about the
> > machine's short comings from your perspective?
> 
> Firstly let me emphasise that my first computer was
> a
> TRS-80 Model 1. And 
> I thus do have a soft spot for that machine.
> Irrational, probably, but 
> there you are. I've got several TRS-80s now (M1, M3,
> M4, CoCo, M100) and 
> all have proved _very_ reliable. Odd considering
> other
> people's 
> expieneces, but I must have replaced perhaps a dozen
> components _total_ 
> in all said machines. 

I see nothing wrong with that. The Tandy machines
seemed like decent computers for the money. I wouldn't
mind picking up a TRS-80 someday.
 
> Now, the Apple ][...
> I had a lot of rpboelsm with it randomly crashing.
> In
> the end I took the 
> whole thing apart and stuck an ammeter in the 5V
> output of the power 
> supply. It turend out that the mainboard (48K RAM) +
> languge caed + 1 
> floppy drive drew _more_ than the rated current of
> the
> supply as given in 
> the techincal manual If you added more drives, a
> serial card, etc, it 
> became ridiculous.

Strange, I haven't noticed any stability problems with
my ][ and ][+ under similar loads. Still, an unstable
machine is unlikely to impress.
 
> Much has been said about the Apple ][ disk
> controlle,
> and how it's a 
> clever design. Well, a minimal-component design
> certainly, but I didn't 
> like it. Not having a track0 sensor seemed like a
> Bad
> thing for starters 
> (continually banging the head against the stop does
> not improve the 
> alignemnt!). The drives are Shugart mechanisms with
> the IMHO poor 
> plastic-cam-with-a-spiral-groove head positioner,
> and
> becuase the drives 
> are non-standard you can't use any others (unlike
> the
> TRS-80 where you 
> can use any 5.25", 3.5" or 3" drives). But for me
> the
> biggest problem was 
> that the Apple couldn't read/write disks from other
> machines, unlike the 
> TRS-80, which used a WD1771 controller and could
> handle any single-desity 
> 5.25" disk (I spent many late nights getting it to
> read the disks from 
> the school's RML380Z computers, which also used 1771
> controllers).

What can I say? The Disk II, either you love it or you
hate it. :) 

To be fair though, the Apple Disk II system was not
the only game in town. While they weren't common, you
could get a 3rd party 8" MFM floppy system if you
wanted to. 

Would you recoil in horror if I told you that some
companies made single sided 40 track 3" (Amdisk) and
double sided 80 track 5.25" (Rana Elite 3) drives for
use with the original Disk II controller? ;)
 
> I didn't like the Apple ][ I/O system. Memory space
> was tight, but they 
> wasted lots of space with those 'soft switches' and
> single-bit inputs. It 
> could all have been packed into a few bytes. I am
> pretty sure the 6821 if 
> not the 6522 was available when the Apple ][ was
> designed.

Fair enough.

> The first seiral port for the Apple ][ was a
> bit-banger. It was the only 
> one I had for some time, and it was almost unusable.
> The TRS-80 used a 
> real UART, and worked. Yes, there were better serial
> ports avaiable for 
> the Apple later.

Was this an early serial board or were you using the
game port? I've always enjoyed the luxury of a 6551
equiped board (Super Serial Card II).

I think Woz was allergic to peripheral chips in the
beginning. :)

> The Apple text display did have lower case (wich the
> TRS-80 didn't as 
> standard), but you couldn't mix text and graphics on
> the same part of the 
> screen. Apple gave you the high-res mode, but
> working
> out the addresses 
> gave me headaches (all to save a few chips IMHO!).
> And
> colours in the 
> high-res mode were essentially obtained as NTSC
> artefacts.

The TRS-80 graphic characters are pretty neat. The
stock Apple character generator was certainly poor in
terms of graphics characters. Heck, it didn't have
lower case characters! Needless to say, soft hires
character generators were a pretty common project. It
would have been nice to have had one in the firmware.

The hires mode is somewhat byzantine and it was indeed
that way to save chips! :) Fortunately, it's not too
bad to work with if you use a lookup table to untangle
the memory map. I have no doubt it has turned off
plenty of people though.

The colors are NTSC artifacts! :) I thought that was a
neat hack. How did they deal with that in PAL land?

> And another oddiity. The whole design of the Apple
> ][
> seems to have been 
> to save a chip if at all possible (provided the
> machine still works -- 
> just).

Bingo! Legend has it that Woz's aesthetic ideal was to
bum a design down to as few chips as possible. Almost
a  Madman Muntz I suppose. 

Methinks you're not a fan of Clive Sinclair either? :)

 And yet the kayboard was encoded in hardware.
> Why? It meant you 
> couldn't implelement a lower case keyboard in
> software
> (there are the 
> well-known shift key mods where you run a wire from
> the shift keyswitch 
> to one of the single-bit inputs on the games
> connector, which shouldn't 
> have been necessary).

This is a good point. My guess would be that Woz
designed the Apple II as just a naked board, kind of
like the Apple I. Apple sold you the motherboard and
it was up to you to find a power supply , keyboard,
and housing. Apple did offer the ][ that way early on.

> Of course I like elegant, simple designs (the HP9100
> is a case in point). 
> But the Apple ][ seems to have been a case of
> cutting
> too many corners. 
> And I had a lot of problems as a reuslt. 
> 
> -tony

Thanks for your input Tony. While I've never had
reliability problems with my ][/ ][+ I think I
understand where you're coming from. I like the Apple
because I feel it's a machine with interesting
capabilities yet made from a small amount of simple
parts. It's a machine I can both grasp and enjoy.

What's your opinion of the BBC Micro? I've never had
the pleasure of using one, but on paper it sounds a
lot like a fast Apple II with a pair of 6522, 6845,
hardware ACIA, 1770 FDC, and enhanced basic.

Liam Busey


 
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