4 Feb
2007
4 Feb
'07
8:01 a.m.
Tony Duell wrote:
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.
I never had a problem like that, and the Apple ][s I used all had at
least two drives, and most had several extra cards in them.
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.
Neither did I, for much the same reasons. And I had to repair quite a
few that went out of alignment, and some that had released the magic
smoke when someone plugged the drives in "off by one" after they
disconnected them to move the machine.
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 6820 (and 6520) and 6522 existed then.
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 Apple didn't have lower case. The normal Apple ][ character
generator ROM only had enough space for upper case in its 64-character
set, and the later ones in the (Euro)plus from the Rev 07 boards onwards
(the ones that didn't need RAM config blocks) didn't provide lower case
unless you replaced the chargen ROM with an EPROM of your own. The only
way to get lower case on an unmodified Apple ][ or ][+ was to use the
High Res Character Generator (HRCG) routines which came with the Hi-Res
toolkit, and they were s..l..o..w.. and icky and of course required you
to put the thing in Hi-Res mode.
Worst of all for me, though, was that there weren't enough keys on the
keyboard, and as a result there were some characters it simply couldn't
generate, like underscore and '[' and a few control-characters. IIRC
there was a mod for later keyboards to provide upper and lower-case
codes, but it wasn't enabled by default and there were still too few keys.
Hi-res addressing was unusually complicated, I agree. And the colour
limitations were interesting, even for users that had PAL video cards.
--
Pete Peter Turnbull
Network Manager
University of York