15 Nov
2000
15 Nov
'00
11:22 p.m.
>> Besides, a 4-bit address bus seems utterly,
utterly limited.
> For most of those the data path was 4bits the address path was often 12
> or more bits.
[*] Keeping address pointers in the memory and
peripheral chips has
a long history. The Intel 4004 and 4040, the Fairchild F8, and
other processors have done this. IIRC, the F8 also used the dual
data pointer concept. Whereas on the Saturn bus, neither data pointers
is "special", with the F8 one of them is explicitly designated to be the
program counter.
And to bring this down to a more common known device:
The TI 99/4(A) did use so called GROMs - ROM chips
where you could set an address pointer and then read
consecutive bytes from the read port. Quite handy
for interpreted languages where you access your
program sequencialy - and in fact most TI soft,
wven the Basic interpreter itself is written in
an interpreted language. And even more, the Basic
programms where stored not in amin memory, but rather
in Video Memory - which is seperate, and again
addressed thru a similar port logic (including write
this time). If it wouldn't be for some small quirks,
the 99/4 would be a premium design - I'd considere
it superior to almost all other home/personal units
at the same time. Unusual, but great - you almost feel
that this system has been developed by guys working on
'big' systems, and not the usual micro processor geek.
Gruss
H.
(Did I mention that I started to programm th TI some
weeks ago ? :))
--
VCF Europa 2.0 am 28./29. April 2001 in Muenchen
http://www.vintage.org/vcfe
http://www.homecomputer.de/vcfe