"Geoffrey G. Rochat" writes:
....[snip]....
You can do an awful lot on a computer with only 8 instructions that can
directly address a mere 256 12-bit words at a time - if you're willing to
think a little bit. PDP-8s are to computers what regens are to radios:
....[snip]....

You can also do an awful lot on a computer with only 8 instructions that
can directly address only THIRTY-TWO NINE-bit words at a time:

In 1969, while at Fairchild R&D Lab in Palo Alto, CA, I designed and
built a 9-bit PDP-8 imitation (I called it "MINUS", since it was smaller
than a mini-computer; if I had called it "MICRO", I might now be rich!)
with 512 9-bit words of 200 nsec memory. Its instruction format used
a: 3 bit opcode,
1 bit current page/page zero indicator,
1 bit indirect indicator, and a
4 bit address

I also wrote a cross-assembler (in FORTRAN) for it, interfaced it to a
20Kbyte/second magnetic tape and a 3-foot x 5-foot flat bed plotter,
and wrote a program (in MINUSASM) which, in a tight loop, read mag-tape
printed-circuit wirelists produced on an IBM 360/44, buffered them in
the upper half of memory, and then passed them to the plotter to draw
large PC boards. Just before quiting time, we'd load a new mag tape,
and 5-6 hours later another board had been drawn in three colors
(horizontal, vertical, and vias).

Ah, those were the heady days of youth!

--Myron A. Calhoun.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

My first CPU, designed and built as a lab project in 1971, used 16-bit
registers and memory words, but the data paths were 1-bit serial. The memory
was implemented with a ~9ms acoustic delay line, in which 8192 recirculating
bits were stored. One of the neat aspects of this design is that one could
continuously view all of memory with a single scope probe! It was unique in
its use of a then-newfangled touchtone keypad for entering hexadecimal
values into registers, replacing the individual toggle switches customarily
used for that purpose. To prove its completion, we programmed it to perform
BCD division; after literally seconds of flashing the lights attached to its
registers, it halted with the correct result ablaze and the TA intoned "it
lives". It was a defining moment...

73,

Dave, AA6YQ


wrote in message ...
"Geoffrey G. Rochat" writes:
....[snip]....
You can do an awful lot on a computer with only 8 instructions that can
directly address a mere 256 12-bit words at a time - if you're willing to
think a little bit. PDP-8s are to computers what regens are to radios:
....[snip]....

You can also do an awful lot on a computer with only 8 instructions that
can directly address only THIRTY-TWO NINE-bit words at a time:

In 1969, while at Fairchild R&D Lab in Palo Alto, CA, I designed and
built a 9-bit PDP-8 imitation (I called it "MINUS", since it was smaller
than a mini-computer; if I had called it "MICRO", I might now be rich!)
with 512 9-bit words of 200 nsec memory. Its instruction format used
a: 3 bit opcode,
1 bit current page/page zero indicator,
1 bit indirect indicator, and a
4 bit address

I also wrote a cross-assembler (in FORTRAN) for it, interfaced it to a
20Kbyte/second magnetic tape and a 3-foot x 5-foot flat bed plotter,
and wrote a program (in MINUSASM) which, in a tight loop, read mag-tape
printed-circuit wirelists produced on an IBM 360/44, buffered them in
the upper half of memory, and then passed them to the plotter to draw
large PC boards. Just before quiting time, we'd load a new mag tape,
and 5-6 hours later another board had been drawn in three colors
(horizontal, vertical, and vias).

Ah, those were the heady days of youth!

--Myron A. Calhoun.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and
cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785)
539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle,
Pistol)

My first CPU, designed and built as a lab project in 1971, used 16-bit
registers and memory words, but the data paths were 1-bit serial. The memory
was implemented with a ~9ms acoustic delay line, in which 8192 recirculating
bits were stored. One of the neat aspects of this design is that one could
continuously view all of memory with a single scope probe! It was unique in
its use of a then-newfangled touchtone keypad for entering hexadecimal
values into registers, replacing the individual toggle switches customarily
used for that purpose. To prove its completion, we programmed it to perform
BCD division; after literally seconds of flashing the lights attached to its
registers, it halted with the correct result ablaze and the TA intoned "it
lives". It was a defining moment...

73,

Dave, AA6YQ


wrote in message ...
"Geoffrey G. Rochat" writes:
....[snip]....
You can do an awful lot on a computer with only 8 instructions that can
directly address a mere 256 12-bit words at a time - if you're willing to
think a little bit. PDP-8s are to computers what regens are to radios:
....[snip]....

You can also do an awful lot on a computer with only 8 instructions that
can directly address only THIRTY-TWO NINE-bit words at a time:

In 1969, while at Fairchild R&D Lab in Palo Alto, CA, I designed and
built a 9-bit PDP-8 imitation (I called it "MINUS", since it was smaller
than a mini-computer; if I had called it "MICRO", I might now be rich!)
with 512 9-bit words of 200 nsec memory. Its instruction format used
a: 3 bit opcode,
1 bit current page/page zero indicator,
1 bit indirect indicator, and a
4 bit address

I also wrote a cross-assembler (in FORTRAN) for it, interfaced it to a
20Kbyte/second magnetic tape and a 3-foot x 5-foot flat bed plotter,
and wrote a program (in MINUSASM) which, in a tight loop, read mag-tape
printed-circuit wirelists produced on an IBM 360/44, buffered them in
the upper half of memory, and then passed them to the plotter to draw
large PC boards. Just before quiting time, we'd load a new mag tape,
and 5-6 hours later another board had been drawn in three colors
(horizontal, vertical, and vias).

Ah, those were the heady days of youth!

--Myron A. Calhoun.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and
cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785)
539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle,
Pistol)

"Geoffrey G. Rochat" writes:
....[snip]....
You can do an awful lot on a computer with only 8 instructions that can
directly address a mere 256 12-bit words at a time - if you're willing to
think a little bit. PDP-8s are to computers what regens are to radios:
....[snip]....

You can also do an awful lot on a computer with only 8 instructions that
can directly address only THIRTY-TWO NINE-bit words at a time:

In 1969, while at Fairchild R&D Lab in Palo Alto, CA, I designed and
built a 9-bit PDP-8 imitation (I called it "MINUS", since it was smaller
than a mini-computer; if I had called it "MICRO", I might now be rich!)
with 512 9-bit words of 200 nsec memory. Its instruction format used
a: 3 bit opcode,
1 bit current page/page zero indicator,
1 bit indirect indicator, and a
4 bit address

I also wrote a cross-assembler (in FORTRAN) for it, interfaced it to a
20Kbyte/second magnetic tape and a 3-foot x 5-foot flat bed plotter,
and wrote a program (in MINUSASM) which, in a tight loop, read mag-tape
printed-circuit wirelists produced on an IBM 360/44, buffered them in
the upper half of memory, and then passed them to the plotter to draw
large PC boards. Just before quiting time, we'd load a new mag tape,
and 5-6 hours later another board had been drawn in three colors
(horizontal, vertical, and vias).

Ah, those were the heady days of youth!

--Myron A. Calhoun.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

Geoffrey G. Rochat wrote:
kenneth scharf wrote in message
...

Does anybody know where I can get a Harris or Intersil
HD6100, HD6120, IM6100, or IM6120 microprocessor (cmos pdp-8)?

I used to work for Digital, and thought it would be an interresting

project

to homebrew a PDP-8 system. I have a T11 microprocessor chip in the

junbox

someplace, so a PDP-11 system is also a possibility.




In fact, there is a fellow who sells kits and parts for the SBC6120, which
is a build-your-own PDP-8 based on the IM6120 chip:

http://www.sparetimegizmos.com/Hardware/SBC6120-2.htm

And this fellow has an add-on for the SBC6120:

http://www.jkearney.com/sbc6120/iob6120.htm

Also, IM6100 chips show up on eBay from time to time.

PDP-8 documentation may be found at Al Kossow's site:

http://www.spies.com/~aek/pdf/dec/pdp8/

And at Dave Gesswein's site:

http://www.pdp8.net

Also, Bob Supnik's SIMH retrocomputing simulator supports the PDP-8. SIMH
is hosted at Tom Shoppa's Trailing Edge site, currently down due to the
effects of Isabel:


Now that's a name I haven't heard for a while. I worked with Bob at DEC
some 25 years ago.
Bob's the nerd that translated the Dungeon (aka Zork) game from Muddle into
Fortran to port it from the PDP-10 to the PDP-11 under RT11

Geoffrey G. Rochat wrote:
kenneth scharf wrote in message
...

Does anybody know where I can get a Harris or Intersil
HD6100, HD6120, IM6100, or IM6120 microprocessor (cmos pdp-8)?

I used to work for Digital, and thought it would be an interresting

project

to homebrew a PDP-8 system. I have a T11 microprocessor chip in the

junbox

someplace, so a PDP-11 system is also a possibility.




In fact, there is a fellow who sells kits and parts for the SBC6120, which
is a build-your-own PDP-8 based on the IM6120 chip:

http://www.sparetimegizmos.com/Hardware/SBC6120-2.htm

And this fellow has an add-on for the SBC6120:

http://www.jkearney.com/sbc6120/iob6120.htm

Also, IM6100 chips show up on eBay from time to time.

PDP-8 documentation may be found at Al Kossow's site:

http://www.spies.com/~aek/pdf/dec/pdp8/

And at Dave Gesswein's site:

http://www.pdp8.net

Also, Bob Supnik's SIMH retrocomputing simulator supports the PDP-8. SIMH
is hosted at Tom Shoppa's Trailing Edge site, currently down due to the
effects of Isabel:


Now that's a name I haven't heard for a while. I worked with Bob at DEC
some 25 years ago.
Bob's the nerd that translated the Dungeon (aka Zork) game from Muddle into
Fortran to port it from the PDP-10 to the PDP-11 under RT11

kenneth scharf wrote in message
...
Does anybody know where I can get a Harris or Intersil
HD6100, HD6120, IM6100, or IM6120 microprocessor (cmos pdp-8)?

I used to work for Digital, and thought it would be an interresting
project
to homebrew a PDP-8 system. I have a T11 microprocessor chip in the
junbox
someplace, so a PDP-11 system is also a possibility.



In fact, there is a fellow who sells kits and parts for the SBC6120, which
is a build-your-own PDP-8 based on the IM6120 chip:

http://www.sparetimegizmos.com/Hardware/SBC6120-2.htm

And this fellow has an add-on for the SBC6120:

http://www.jkearney.com/sbc6120/iob6120.htm

Also, IM6100 chips show up on eBay from time to time.

PDP-8 documentation may be found at Al Kossow's site:

http://www.spies.com/~aek/pdf/dec/pdp8/

And at Dave Gesswein's site:

http://www.pdp8.net

Also, Bob Supnik's SIMH retrocomputing simulator supports the PDP-8. SIMH
is hosted at Tom Shoppa's Trailing Edge site, currently down due to the
effects of Isabel:

http://simh.trailing-edge.com

To those of you who chuckle at the OP's questions, I've got a PDP-8/A
sitting about 5ft to my right as I type this, and a another in the basement,
right next to a PDP-8/E, a VT78 (based on the IM6100) and a DECmate II
(based on the IM6120). Just today I was at one place with a third PDP-8/A
which I refurbished a few months ago, a working PDP-8/E, a PDP-8/L in need
of serious help, 3 PDP-12s (essentially PDP-8/Is with added A/D and D/A
I/Os), several DECmates and a LINC-8. Today I also stopped by a place with
a several more DECmates and a PDP-8/L that I and a cohort rescued from the
defunct United Electronics tube factory in Newark, NJ this past spring.
PDP-8 Disease is incurable. Once infected you're happily chronic for life.

You can do an awful lot on a computer with only 8 instructions that can
directly address a mere 256 12-bit words at a time - if you're willing to
think a little bit. PDP-8s are to computers what regens are to radios:
Obsolete, but amazing for what they can do with so little, and a tremendous
pile of fun to play with. In essence they're the spirit of QRP operation as
applied to computers.

Geoffrey G. Rochat
Vice President, Rhode Island Computer Museum (www.osfn.org/ricm)
Member, RetroComputing Society of Rhode Island (www.osfn.org/rcs)