TRS-80 Model I

Tony Duell ard at
Sat Feb 3 18:56:10 CST 2007

> 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. 

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.

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).

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.

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.

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.

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). 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).

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. 


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