13 Apr
2002
13 Apr
'02
3:03 a.m.
Yes, I remember the PW memories on the Honeywell 516-types used as the space
shuttle engine controller. I don't recall that it had a read-only command. I
do remember, however, that since the PW held whatever was last stored, it
could retain a failure from one mission to the next. (PW was 200 ns or so
faster than core, so they used that.)
see below, plz.
Dick
----- Original Message -----
From: "Ben Franchuk" <bfranchuk(a)jetnet.ab.ca>
To: <classiccmp(a)classiccmp.org>
Sent: Friday, April 12, 2002 9:14 PM
Subject: Re: TTL computing
do
My "early" PALs program on the same programmer that programs my bipolar
PROMs,
and my current-generation GALs as well.
nowadays,
What's the right size? You can get 'em in whatever SO type you like, so
they'll "fit." Looking pretty isn't part of that deal, though. A 4:1
mux is
easy as SOP and each macrocell has a DFF in the path if you want it. XOR is
just [A*/B + /A*B].
Some guys are doing it. The Americas Cup bears witness to that doesn't it?
One of my friends is building a sailboat in one of his vacant buildings. He's
been talking about pouring the keel any day now. I want to see that! He says
he wants to sail it around the world. I hope he makes it.
Richard Erlacher wrote:
> I hope you're not suggesting that devices that use core memories are in
any
way BETTER
than more modern machines that use semiconductor memory.
Core memory had it's day. However it had the advantage of non-volitile
that is hard to duplicate in modern memory. The read/write memory cycle
was well used by computer architecture of the 1960's.
> A PAL can generate any combinatorial function of its inputs. A prom can that too, but
the PAL does it with fewer fuses.
Did not the early PAL's burn on PROM programers? (512x8 fuse prom)
Sadly this not true today.
> Before people draw those schematics, they first manipulate the concepts on
a
> big dry-mark-board (whiteboard), waving their
arms and arguing vehemently
that
> their take is the one. Once the blocks have been
mapped into the
> requirements, low-level design meetings are held where they do the same
thing,
> only at more detail. That's where the block
that later becomes a PLD is
born.
> Block 6B divides the clock by 1-1/2 to generate
the clock you need and
then
> propagates the appropriately divided output to
block 5D which demodulates
the
> data and passes it to the framing logic in block
2G. Three different guys
> design those blocks, and they're later implemented in separate PALs, or in
a
single PLD.
And marketing droids sit on the design 'Go ahead' for months and then
want it yesterday.
> They're state machines, but nobody uses them except for repair parts
> since it's more efficient and cheaper to have
100 GALs costing well under
a
> dollar and not having to track stock and worry
availability. For simple
> logic, I always have some 22V10's, 20RA10's, 16V8's and a few 20V8's
around
> just for the case where I need some function I
don't have in TTL. I don't
> usually buy the TTL any longer unless it's for a repair. I do scrap old
> hardware and save the parts, since that saves me driving around. I do
have a
tester, after
all.
I use TTL because 1) I don't have programmer ( got any schematic for one
that does not use PAL's and easy to find TTL) 2) PALs never are the
right size to replace simple but messy logic -- say a D-F/F followed by
a 4/1 multiplexer followed a xor gate and another D-F/F.
> I know that wooden ships were a beautiful and quiet solution to the
problem
of
> how to get from England to Central America, but
there are lots of them on
the
> bottom of the ocean, and I'd rather take my
chances with a 747. Does that
> mean that flying is better than sailing, well, maybe not, but it is the
method
> of choice, for most of us, nowadays. If I have
two weeks and a lot of
budget,
> I like cruising, but if I have to be at a meeting
tomorrow, and don't want
to
put on ten
pounds, then I fly.
Old sailing ships used a lot of man-power. While OIL is cheap wind
powered modern ships will not be developed.