4 Feb
2007
4 Feb
'07
9:30 a.m.
On 2/4/07, Pete Turnbull <pete at dunnington.plus.com> wrote:
The 6520 == 6821 FWIW. I don't recall how much those were, but new
6522 VIAs were $8 quantity 1 in the early 1980s, so I think Woz may
have just shied away from them on the basis of cost alone. I did
enjoy learning how to twiddle the PET user port on a 4K PET. More
complicated than the Apple scheme (data direction registers,
interrupts, etc.), but vastly more powerful.
-ethan
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.
That was a problem I also saw with the drives. Several of my friends
had Apple IIs (I had a 32K PET 2001-N), and ISTR more than one person
did that. Not cheap. My memory is that at the time, the bare drives
were $600 new, so even if one just replaces boards, it's not
inexpensive in that environment.
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.