16 Jul
2001
16 Jul
'01
7:48 p.m.
There's no doubt about it, Mike, the Apple was quite useful for a lot of things.
I simply pointed out that with a different device, costing about $90 rather than
the considerably more that an Apple][ cost back in '79, you could do much of the
same stuff, unfettered by the restrictions that the Apple hardware put on you.
Now, I don't remember what an Apple proto card cost back then (I still have one
of those I bought back in '80) but those were bought to build a HDC for the
Apple.
I find the 6801L1 quite a bit better for dealing with the basics of handling
microprocessor related issues, since they don't have the video timing logic
defining the clock rate. That's not because the Apple is bad, but because it's
easier to deal with the naked processor than the entire system. Having the
ability to define a clock rate based on your application needs rather than those
of the video timing makes it possible to save on costs and effort. Many
applications, particularly those of low volume, make it cheaper, overall, simply
to build an Apple, or, nowadays, a PC into the solution.
Dick
----- Original Message -----
From: "Mike Ford" <mikeford(a)socal.rr.com>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, July 16, 2001 2:09 PM
Subject: Re: Apple II for intro to microprocessors
While there are
a lot of processor-application-related things you are
prevented
from, or at least, restricted in, accomplishing because of the restrictions
placed on the hardware by the design of the platform, there certainly isn't
anything you can't do from a computing standpoint. However, that was my
point.
The things that define a microprocessor-based system are fixed in the Apple,
mostly by its video timing restrictions, but also by its memory map and
the way
in which I/O is managed.
ONLY if you restrict yourself entirely to the Apple II hardware. Anything I
couldn't directly do internally on the Apple I could put on a protocard and
just use the Apple as a convient disc drive and display.
There's no question that one had to read quite
a bit. However, most of the
materials written about microprocessors were really dedicated to
microcomputing
rather than the application of microprocessors. Device manufacturers
weren't of
much help either because they wanted you to buy their particular development
systems, with their limitations, and those didn't often help very much.
What I was refering to in books were timing diagrams, not how to write a
new version of CheckBook. My work in embedded control was as much about
gate delays as gosubs. I never ran into the "restrictions" and found the
Apple II a very convient platform to develope from. A 6520 on a cheap Apple
II I/O card doesn't behave very differently from the same chip on a
protoboard as part of a 6502 based controller. Many many apples crossed my
bench and sat on my desk with a loom of wires trailing out the back to
simulate some process before the "real" boards were ready.