16 Dec
2001
16 Dec
'01
6:37 a.m.
-----Original Message-----
From: Ben Franchuk <bfranchuk(a)jetnet.ab.ca>
> Sure its trivial to do now but we were talking
1981 when PALS were
> expensive.
Yes, they were compared to random logic, but if board space was costly
they were cheaper.
I never heard about pal's until about 1990. In some
ways the peripheral
PALS are 1970s technology, really old to some of us.
chips are in a really sorry shape. You have vintage
slow I/O (2 MHZ?)
or PC motherboard chip sets. Nothing in between. On my FPGA I can run
with a 250 ns memory cycle, but need to stretch it to 625 ns for I/O.
Actually thats not true. BY 1981 you have peripherals in the 125ns read
write timing range. Then again Z80 at that time was just hinting at 6mhz
so z80 peripherals were of an according spped for that cpu. However,
other
parts were faster and often far cheaper.
Personally if I wanted the SIO functionality for a NON-z80 system I'd
never use the zilog part. Reason it was not cheap,nor was it easy to
use for non-z80 systems. They were designed for the Z80, period.
Unfortunatly they were slow. If you wanted faster the 83xx or 85xx
parts from Zilog were a far better choice but Zbus was scary to most
people and they weren't cheap. The other part of this is NEC and
Intel did the MPSC (NEC D7201, INtel 8274) which was functionally
identical to the SIO and was "tuned" for 8080/8085/8088/8086 style
busses and faster as well. It was a more generic part than the SIO.
Also around that time Signetics and friends were doing the 2681 part
that was cheap and available in various flavors. Peripherals back then
were quite varied.
Allison
16 Dec
16 Dec
8:31 a.m.
ajp166 wrote:
PALS are 1970s technology, really old to some of us.
Arg! And here I thought the 8008 was 70's technology.
Actually thats not true. BY 1981 you have peripherals
in the 125ns read
write timing range. Then again Z80 at that time was just hinting at 6mhz
so z80 peripherals were of an according spped for that cpu. However,
other
parts were faster and often far cheaper.
If you must know it is a floppy disk controller I need. Right now
I plan to use WD2797 floppy disk controller. I would love to use
a newer chip,but I can't find any! I want to stay with DIP's and PLCC's
here. This may be the 21 century but my soldering skills are the 19'th.
Personally if I wanted the SIO functionality for a
NON-z80 system I'd
never use the zilog part. Reason it was not cheap,nor was it easy to
use for non-z80 systems. They were designed for the Z80, period.
Unfortunatly they were slow. If you wanted faster the 83xx or 85xx
parts from Zilog were a far better choice but Zbus was scary to most
people and they weren't cheap. The other part of this is NEC and
Intel did the MPSC (NEC D7201, INtel 8274) which was functionally
identical to the SIO and was "tuned" for 8080/8085/8088/8086 style
busses and faster as well. It was a more generic part than the SIO.
Also around that time Signetics and friends were doing the 2681 part
that was cheap and available in various flavors. Peripherals back then
were quite varied.
I still favor the simple dumb uart chip. TR1602?. I like things than
you hit reset, it starts ... not like the classic star-trek computers
that always
go down. Usually when you need them.
--
Ben Franchuk --- Pre-historic Cpu's --
www.jetnet.ab.ca/users/bfranchuk/index.html
9:12 a.m.
On Sun, 16 Dec 2001, Ben Franchuk wrote:
Actually Its possible to do QFPs pretty easy with just a good soldering
iron and lots of flux... Even BGA's aren't too hard with a hot air gun
(surface tension does the work)
Can you still get TR1602's? I remember building something with them (maybe
it was a 1402) and 3341 FIFO's in the 70's
Peter Wallace
ajp166 wrote:
Well more into the 80s since the PAL was invented in 1978...
PALS are 1970s technology, really old to some of
us.
Arg! And here I thought the 8008 was 70's technology. Actually thats not true. BY 1981 you have
peripherals in the 125ns read
write timing range. Then again Z80 at that time was just hinting at 6mhz
so z80 peripherals were of an according spped for that cpu. However,
other
parts were faster and often far cheaper.
If you must know it is a floppy disk controller I need. Right now
I plan to use WD2797 floppy disk controller. I would love to use
a newer chip,but I can't find any! I want to stay with DIP's and PLCC's
here. This may be the 21 century but my soldering skills are the 19'th. Personally if I wanted the SIO functionality for
a NON-z80 system I'd
never use the zilog part. Reason it was not cheap,nor was it easy to
use for non-z80 systems. They were designed for the Z80, period.
Unfortunatly they were slow. If you wanted faster the 83xx or 85xx
parts from Zilog were a far better choice but Zbus was scary to most
people and they weren't cheap. The other part of this is NEC and
Intel did the MPSC (NEC D7201, INtel 8274) which was functionally
identical to the SIO and was "tuned" for 8080/8085/8088/8086 style
busses and faster as well. It was a more generic part than the SIO.
Also around that time Signetics and friends were doing the 2681 part
that was cheap and available in various flavors. Peripherals back then
were quite varied.
I still favor the simple dumb uart chip. TR1602?. I like things than
you hit reset, it starts ... not like the classic star-trek computers
that always
go down. Usually when you need them.
--
Ben Franchuk --- Pre-historic Cpu's --
www.jetnet.ab.ca/users/bfranchuk/index.html
1:44 p.m.
see below, plz.
Dick
----- Original Message -----
From: "Peter C. Wallace" <pcw(a)mesanet.com>
To: <classiccmp(a)classiccmp.org>
Sent: Sunday, December 16, 2001 4:12 PM
Subject: Re: MITS 2SIO serial chip?
Actually Its possible to do QFPs pretty easy with just a good soldering
iron and lots of flux... Even BGA's aren't too hard with a hot air gun
(surface tension does the work)
I always liked them, too,
except for the space they required, including the
external clock generator(s).
I remember an ad not long ago that listed, among other things, the 1602. I've
not seen the 3341 for quite a long while, since there are CMOS versions.
On Sun, 16 Dec 2001, Ben Franchuk wrote:
I've stumbled over a 1978 databook from MMI this weekend a couple of times,
that
suggests the 16L/R/X/A series is new product in 1978, but there were quite a few
PALs that predate them. Signetics had a different sort of device than MMI, that
also goes back to the '70's.
ajp166 wrote:
Well more into the 80s since the PAL was invented in 1978...
PALS are 1970s technology, really old to some of
us.
Arg! And here I thought the 8008 was 70's technology. Actually thats not true. BY 1981 you have
peripherals in the 125ns read
write timing range. Then again Z80 at that time was just hinting at 6mhz
so z80 peripherals were of an according spped for that cpu. However,
other
parts were faster and often far cheaper.
If you must know it is a floppy disk controller I need. Right now
I plan to use WD2797 floppy disk controller. I would love to use
a newer chip,but I can't find any! I want to stay with DIP's and PLCC's
here. This may be the 21 century but my soldering skills are the 19'th. Personally if I wanted the SIO functionality for
a NON-z80 system I'd
never use the zilog part. Reason it was not cheap,nor was it easy to
use for non-z80 systems. They were designed for the Z80, period.
Unfortunatly they were slow. If you wanted faster the 83xx or 85xx
parts from Zilog were a far better choice but Zbus was scary to most
people and they weren't cheap. The other part of this is NEC and
Intel did the MPSC (NEC D7201, Intel 8274) which was functionally
identical to the SIO and was "tuned" for 8080/8085/8088/8086 style
busses and faster as well. It was a more generic part than the SIO.
Also around that time Signetics and friends were doing the 2681 part
that was cheap and available in various flavors. Peripherals back then
were quite varied.
I still favor the simple dumb uart chip. TR1602?. I like things than
you hit reset, it starts ... not like the classic star-trek computers
that always go down. Usually when you need them. --
Ben Franchuk --- Pre-historic Cpu's --
www.jetnet.ab.ca/users/bfranchuk/index.html
Can you still get TR1602's? I remember building something with them (maybe
it was a 1402) and 3341 FIFO's in the 70's
Peter Wallace
17 Dec
17 Dec
3:19 a.m.
On Sun, 16 Dec 2001, Richard Erlacher wrote:
Actually Its possible to do QFPs pretty easy with just a good soldering
iron and lots of flux... Even BGA's aren't too hard with a hot air gun
(surface tension does the work)
I always liked them, too,
except for the space they required, including the
external clock generator(s).
I remember an ad not long ago that listed, among other things, the 1602.
I've
not seen the 3341 for quite a long while, since there are CMOS versions.
Peter Wallace
Mesa Electronics
see below, plz.
Dick
----- Original Message -----
From: "Peter C. Wallace" <pcw(a)mesanet.com>
To: <classiccmp(a)classiccmp.org>
Sent: Sunday, December 16, 2001 4:12 PM
Subject: Re: MITS 2SIO serial chip?
There were earlier programmable logic parts, but the PAL was invented in
in 1978 by Birkner and Chua...
On Sun, 16 Dec 2001, Ben Franchuk wrote:
I've stumbled over a 1978 databook from MMI this weekend a couple of times,
that
suggests the 16L/R/X/A series is new product in 1978, but there were quite a few
PALs that predate them. Signetics had a different sort of device than MMI, that
also goes back to the '70's. ajp166 wrote:
Well more into the 80s since the PAL was invented in 1978...
PALS are 1970s technology, really old to some of
us.
Arg! And here I thought the 8008 was 70's technology. Actually thats not true. BY 1981 you have
peripherals in the 125ns read
write timing range. Then again Z80 at that time was just hinting at 6mhz
so z80 peripherals were of an according spped for that cpu. However,
other
parts were faster and often far cheaper.
If you must know it is a floppy disk controller I need. Right now
I plan to use WD2797 floppy disk controller. I would love to use
a newer chip,but I can't find any! I want to stay with DIP's and PLCC's
here. This may be the 21 century but my soldering skills are the 19'th. Personally if I wanted the SIO functionality for
a NON-z80 system I'd
never use the zilog part. Reason it was not cheap,nor was it easy to
use for non-z80 systems. They were designed for the Z80, period.
Unfortunatly they were slow. If you wanted faster the 83xx or 85xx
parts from Zilog were a far better choice but Zbus was scary to most
people and they weren't cheap. The other part of this is NEC and
Intel did the MPSC (NEC D7201, Intel 8274) which was functionally
identical to the SIO and was "tuned" for 8080/8085/8088/8086 style
busses and faster as well. It was a more generic part than the SIO.
Also around that time Signetics and friends were doing the 2681 part
that was cheap and available in various flavors. Peripherals back then
were quite varied.
I still favor the simple dumb uart chip. TR1602?. I like things than
you hit reset, it starts ... not like the classic star-trek computers
that always go down. Usually when you need them. --
Ben Franchuk --- Pre-historic Cpu's --
www.jetnet.ab.ca/users/bfranchuk/index.html
Can you still get TR1602's? I remember building something with them (maybe
it was a 1402) and 3341 FIFO's in the 70's
Peter Wallace
12:17 p.m.
What sorts of programmable logic did you have in mind as being around before
PALs? PROMs, perhaps?
I don't know who invented 'em, but It doesn't matter to me. They were a good
idea and were in very wide use by 1979. By that time we frequently inquired as
to whether a board used PALs before deciding whether or not to buy the board
becuase repair was costly if you had to pay $15 for a $2 PAL, and we'd already
learned our lesson with PROMs used in decoders.
Dick
----- Original Message -----
From: "Peter C. Wallace" <pcw(a)mesanet.com
To: <classiccmp(a)classiccmp.org
Sent: Monday, December 17, 2001 10:19 AM
Subject: Re: MITS 2SIO serial chip?
> > > >
Actually thats not true. BY 1981 you have peripherals in the 125ns read
Where serial I/O is concerned, that being a laboriously slow
process, speed is
of little interest. The problem, of course, was that while the Z80B was "out"
in '80-'81, the 'B'-series peripherals were not.
<snip
> > > > > > > I
still favor the simple dumb uart chip. TR1602?. I like things than
> > > > you hit reset, it starts ... not like the classic star-trek computers
> > > > that always go down. Usually when you need them.
> > > > I always
liked them, too, except for the space they required, including the
> > external clock generator(s).
> > > > --
> > > > Ben Franchuk --- Pre-historic Cpu's --
> > > > www.jetnet.ab.ca/users/bfranchuk/index.html
> > > > > > > > Can you still get TR1602's? I
remember building something with them (maybe
> > > it was a 1402) and 3341 FIFO's in the 70's
> > > > I remember
an ad not long ago that listed, among other things, the 1602.
I've
> > not seen the 3341 for quite a long while, since there are CMOS versions.
> > > > > Peter
Wallace
> > > > > >
> >
> Peter Wallace
> Mesa Electronics
On Sun, 16 Dec 2001, Richard Erlacher wrote:
> see below, plz.
> Dick
> ----- Original Message -----
> From: "Peter C. Wallace" <pcw(a)mesanet.com
> To: <classiccmp(a)classiccmp.org
> Sent: Sunday, December 16, 2001 4:12 PM
> Subject: Re: MITS 2SIO serial chip?
> > On Sun, 16 Dec 2001, Ben Franchuk wrote:
> > > > ajp166 wrote:
> > > > PALS are 1970s technology, really old to some of us.
> > > Arg! And here I thought the 8008 was 70's technology.
> > > Well more into the 80s since the PAL
was invented in 1978...
> > I've stumbled over a 1978 databook
from MMI this weekend a couple of times,
that
> suggests the 16L/R/X/A series is new product in
1978, but there were quite a
few
> PALs that predate them. Signetics had a
different sort of device than MMI,
that
also goes back
to the '70's.
There were earlier programmable logic parts, but the PAL was invented in
in 1978 by Birkner and Chua...
> > > > > > write timing range. Then again
Z80 at that time was just hinting at
6mhz
> > >
so z80 peripherals were of an according spped for that cpu. However,
> > > other parts were faster and often far cheaper.
> >
16 Dec
16 Dec
12:55 p.m.
see below, plz.
Dick
----- Original Message -----
From: "Ben Franchuk" <bfranchuk(a)jetnet.ab.ca>
To: <classiccmp(a)classiccmp.org>
Sent: Sunday, December 16, 2001 3:31 PM
Subject: Re: MITS 2SIO serial chip?
ajp166 wrote:
I got my first Z80B (6 MHz)
in early 1981 and Z80H (8 MHz) in 1983.
PALS are 1970s technology, really old to some of
us.
Arg! And here I thought the 8008 was 70's technology.
Actually thats not true. By 1981 you have
peripherals in the 125ns read
write timing range. Then again Z80 at that time was just hinting at 6mhz
so z80 peripherals were of an according spped for that cpu. However,
other parts were faster and often far cheaper.
If you must know it is a floppy disk controller I need. Right now
I plan to use WD2797 floppy disk controller. I would love to use
a newer chip,but I can't find any! I want to stay with DIP's and PLCC's
here. This may be the 21 century but my soldering skills are the 19'th.
Why? The WD37C65 is a much easier part to use, and it programs pretty much like
a NEC uPD765, drives the cable directly, and automatically deals with the
data/clock separation for 500 KHz, 250 KHz, and 125 KHz data rates at both 300
and 360 rpm. You can lift 'em from broken HDC's or order 'em from
www.rocelec.com (Rochester Electronics). They're most common in PLCC-44, which
you should be able to handle, even if, like me, you didn't listen to Mom when
she told you to stop that. If you must use a WD part, which I prefer also, then
use a WD179x with a FDC9229. That does everything in two chips, including
selecting the appropriate clocks. The 2797 uses an analog PLL and, unless you
are satisfied with a single data rate, that means multiple filters and analog
muxes, etc.
Personally if I wanted the SIO functionality for
a NON-z80 system I'd
never use the zilog part. Reason it was not cheap,nor was it easy to
use for non-z80 systems. They were designed for the Z80, period.
Unfortunatly they were slow. If you wanted faster the 83xx or 85xx
parts from Zilog were a far better choice but Zbus was scary to most
people and they weren't cheap. The other part of this is NEC and
Intel did the MPSC (NEC D7201, Intel 8274) which was functionally
identical to the SIO and was "tuned" for 8080/8085/8088/8086 style
busses and faster as well. It was a more generic part than the SIO.
Also around that time Signetics and friends were doing the 2681 part
that was cheap and available in various flavors. Peripherals back then
were quite varied.
I still favor the simple dumb uart chip. TR1602?. I like things than
you hit reset, it starts ... not like the classic star-trek computers
that always go down. Usually when you need them.
--
Ben Franchuk --- Pre-historic Cpu's --
www.jetnet.ab.ca/users/bfranchuk/index.html
10:27 a.m.
Richard Erlacher wrote:
Why? The WD37C65 is a much easier part to use, and it
programs pretty much like
a NEC uPD765, drives the cable directly, and automatically deals with the
data/clock separation for 500 KHz, 250 KHz, and 125 KHz data rates at both 300
and 360 rpm. You can lift 'em from broken HDC's or order 'em from
www.rocelec.com (Rochester Electronics). They're most common in PLCC-44, which
you should be able to handle, even if, like me, you didn't listen to Mom when
she told you to stop that.
It sounds like a nice chip. Since all I have is 3 1/2" 1.44mb drives I
will
have a fixed 500 Khz clock, thus less programing. Also the chips are
cheap
if you can find them $7.25 @ BG micro. I was looking some nec? chips at
Rochester
and they were over $75 each.
If you must use a WD part, which I prefer also, then
use a WD179x with a FDC9229. That does everything in
two chips, including
selecting the appropriate clocks. The 2797 uses an analog PLL and, unless you
are satisfied with a single data rate, that means multiple filters and analog
muxes, etc.
Thanks for the info. While a 2 Mhz machine would have been the speed of
system in the 80's I might as well go to 4 Mhz since the FPGA will run
that fast.
As a side note a 2 Mhz machine is about the same speed as a PDP-8. 1.5us
for a jump.
2.5 us for memory access.
--
Ben Franchuk --- Pre-historic Cpu's --
www.jetnet.ab.ca/users/bfranchuk/index.html
2:45 p.m.
Rochester isn't cheap, but they listed the PLCC-44 parts at $18.10, IIRC. The
last time I bought a WD controller (1979), it cost over $90, so the sticker
shock isn't an issue.
----- Original Message -----
From: "Ben Franchuk" <bfranchuk(a)jetnet.ab.ca>
To: <classiccmp(a)classiccmp.org>
Sent: Sunday, December 16, 2001 5:27 PM
Subject: Re: MITS 2SIO serial chip?
you
Richard Erlacher wrote:
> Why? The WD37C65 is a much easier part to use, and it programs pretty much
like
> a NEC uPD765, drives the cable directly, and
automatically deals with the
> data/clock separation for 500 KHz, 250 KHz, and 125 KHz data rates at both
300
> and 360 rpm. You can lift 'em from broken
HDC's or order 'em from
> www.rocelec.com (Rochester Electronics). They're most common in PLCC-44,
which
> you should be able to handle, even if, like me,
you didn't listen to Mom
when
she told you
to stop that.
It sounds like a nice chip. Since all I have is 3 1/2" 1.44mb drives I
will
have a fixed 500 Khz clock, thus less programing. Also the chips are
cheap
if you can find them $7.25 @ BG micro. I was looking some nec? chips at
Rochester
and they were over $75 each.
If you must use a WD part, which I prefer also, then
> use a WD179x with a FDC9229. That does everything in two chips, including
> selecting the appropriate clocks. The 2797 uses an analog PLL and, unless
> are satisfied with a single data rate, that means
multiple filters and
analog
muxes, etc.
Thanks for the info. While a 2 Mhz machine would have been the speed of
system in the 80's I might as well go to 4 Mhz since the FPGA will run
that fast.
As a side note a 2 Mhz machine is about the same speed as a PDP-8. 1.5us
for a jump.
2.5 us for memory access.
--
Ben Franchuk --- Pre-historic Cpu's --
www.jetnet.ab.ca/users/bfranchuk/index.html
2:49 p.m.
Just how does the FPGA fit in here?
With a 179x and a 9229, you need only a pal and an oscillator. With a 2797 and
no need for data rate changes, i.e. 500 KHz only and MFM only, you only need the
2 MHz oscillator for the 2797 and an address decoder with which to generate the
select. You may want some logic to generate the wait-states, else your CPU may
not make it around the horn, so to speak, in a loop that gets in sync and then
stays there at 2 microseconds per bit.
What goes in the FPGA?
Dick
----- Original Message -----
From: "Ben Franchuk" <bfranchuk(a)jetnet.ab.ca>
To: <classiccmp(a)classiccmp.org>
Sent: Sunday, December 16, 2001 5:27 PM
Subject: Re: MITS 2SIO serial chip?
Richard Erlacher wrote:
<snip>
... While a 2 Mhz machine would have been the speed of
system in the 80's I might as well go to 4 Mhz
since the FPGA will run
that fast. As a side note a 2 Mhz machine is about the same speed as a PDP-8.
1.5us
for a jump. 2.5 us for memory access.
--
Ben Franchuk --- Pre-historic Cpu's --
www.jetnet.ab.ca/users/bfranchuk/index.html
12:37 p.m.
Richard Erlacher wrote:
Just how does the FPGA fit in here?
With a 179x and a 9229, you need only a pal and an oscillator. With a 2797 and
no need for data rate changes, i.e. 500 KHz only and MFM only, you only need the
2 MHz oscillator for the 2797 and an address decoder with which to generate the
select. You may want some logic to generate the wait-states, else your CPU may
not make it around the horn, so to speak, in a loop that gets in sync and then
stays there at 2 microseconds per bit.
What goes in the FPGA?
The CPU of course. Most of the last bit of fidgeting has
been getting
the wait states just right. This is a 12/24 bit cpu that has a strong
PDP-8/6809/2901 bitslice influence.The cpu design is a 'what if
scenario' based on a fictional TTL computer of the late 1970's. Version
#1 of the FPGA 1.5 Mhz? - 74LS381-74LS382 ALU, 74189 RAM - auto boot
from paper tape?. Not quite sure when 74LS381's
came out.
Version #2 of the FPGA - Monolithic chip - 3.0 Mhz -better timing -
refresh logic - 40 pin dip - boot from PROM?
About 50% of the FPGA is data path (24 bits). 25% control - 43 states.
25% uart and glue. It all just fits in a Altera 10K10 84 pin PLCC -- 576
logic cells.
At the moment I am using a FPGA prototype board with 32KB of static ram
and
a Maxim buffer for the serial port in the FPGA. A few leds and switches
remain from
debuging the CPU and memory. A old PC is used for program development
and I/O to the
prototype board.
--
Ben Franchuk --- Pre-historic Cpu's --
www.jetnet.ab.ca/users/bfranchuk/index.html
11:10 p.m.
OK ... I missed that somewhere along the way.
Dick
----- Original Message -----
From: "Ben Franchuk" <bfranchuk(a)jetnet.ab.ca>
To: <classiccmp(a)classiccmp.org>
Sent: Sunday, December 16, 2001 7:37 PM
Subject: Re: MITS 2SIO serial chip?
Richard Erlacher wrote:
>
> Just how does the FPGA fit in here?
>
> With a 179x and a 9229, you need only a pal and an oscillator. With a 2797
and
> no need for data rate changes, i.e. 500 KHz only
and MFM only, you only need
the
> 2 MHz oscillator for the 2797 and an address
decoder with which to generate
the
> select. You may want some logic to generate the
wait-states, else your CPU
may
> not make it around the horn, so to speak, in a
loop that gets in sync and
then
stays there at
2 microseconds per bit.
What goes in the FPGA?
The CPU of course. Most of the last bit of fidgeting has
been getting
the wait states just right. This is a 12/24 bit cpu that has a strong
PDP-8/6809/2901 bitslice influence.The cpu design is a 'what if
scenario' based on a fictional TTL computer of the late 1970's. Version
#1 of the FPGA 1.5 Mhz? - 74LS381-74LS382 ALU, 74189 RAM - auto boot
from paper tape?. Not quite sure when 74LS381's came out.
Version #2 of the FPGA - Monolithic chip - 3.0 Mhz -better timing -
refresh logic - 40 pin dip - boot from PROM?
About 50% of the FPGA is data path (24 bits). 25% control - 43 states.
25% uart and glue. It all just fits in a Altera 10K10 84 pin PLCC -- 576
logic cells.
At the moment I am using a FPGA prototype board with 32KB of static ram
and
a Maxim buffer for the serial port in the FPGA. A few leds and switches
remain from
debuging the CPU and memory. A old PC is used for program development
and I/O to the
prototype board.
--
Ben Franchuk --- Pre-historic Cpu's --
www.jetnet.ab.ca/users/bfranchuk/index.html
25 Dec
25 Dec
6:22 a.m.
New subject: PALs (was Re: MITS 2SIO serial chip?)
--- ajp166 <ajp166(a)bellatlantic.net> wrote:
I didn't see PALs in use until the early 1980s. Yes, I know they came
out in 1978, but products designed with them didn't hit right away.
The technology is 1970s, but the products are, for the most part, 1980s.
-ethan
__________________________________________________
Do You Yahoo!?
Send your FREE holiday greetings online!
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-----Original Message-----
From: Ben Franchuk <bfranchuk(a)jetnet.ab.ca>
It depends on what your limited resource is and how costly
_that_ is.
ISTR PALs were $2-$10 each c. 1981-1982. If someone remembers differently,
please supply more accurage data. Yes, a single PAL cost more than several
TTL popcorn chips, but given how much you could fold into a single PAL in
the way of I/O select logic (a common use on the board I first encountered
PALs on), it wasn't so expensive then.
> Sure its trivial to do now but we were
talking 1981 when PALS were
> expensive.
Yes, they were compared to random logic, but if board
space was costly
they were cheaper.
Or if board space was a fixed resource, then it's doubly costly. The
oldest example I can cite from personal experience is the COMBOARD-I
to COMBOARD-II design. Both were early examples of 68000 designs (an
intellegent Unibus serial periperal)... one with SRAM (2114s) and TTL
logic, the other with DRAMs and PALs. One similarity - about 1.5 sq ft.
of board space to cram in a CPU, RAM, support logic, a sync serial port
(based on the COM5025) a parallel port and Unibus DMA logic.
In 1981, our designers went with older tech, but the DMA engine was
horribly complicated from the standpoint of the 68000, but it was in part
because there wasn't enough room on the board for a better design with
TTL. The second revision (c. 1983-1984) had more onboard I/O, and
implemented the DMA engine as a bank of shared memory to the 68000 (i.e.,
read/write to a certain range of memory from your code and it automatically
generates a Unibus DMA cycle - most cool). I don't know for a fact, but
from what I remember about the designs, I don't
think a shared-memory DMA
engine would have fit on a Unibus board if it had been
made out of popcorn
logic.
I never heard
about pal's until about 1990...
PALS are 1970s technology, really old to some of us.
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