22 Mar
2017
22 Mar
'17
3:34 a.m.
OT, but of interest to a few people here :-)
The venerable PDP-8 was introduced in 1965 today (or tomorrow if you're on
the wrong side of the date line). It was the first computer I ever
used, back around 1970 (I think I'd just left school and was checking out
the local University's computer department, with a view to majoring in
Computer Science (which I did)).
--
Dave Horsfall DTM (VK2KFU) "Those who don't understand security will
suffer."
22 Mar
22 Mar
10:34 p.m.
Ah yes, the machine with only 8 instructions (of course not counting all the
multiplexing of OPR).
I was always fond of TAD. Not particularly reentrant version of
subroutine linkage.
-----Original Message-----
From: TUHS [mailto:tuhs-bounces@minnie.tuhs.org] On Behalf Of Dave Horsfall
Sent: Tuesday, March 21, 2017 5:35 PM
To: The Eunuchs Hysterical Society
Subject: [TUHS] Happy birthday, PDP-8!
OT, but of interest to a few people here :-)
The venerable PDP-8 was introduced in 1965 today (or tomorrow if you're on
the wrong side of the date line). It was the first computer I ever used,
back around 1970 (I think I'd just left school and was checking out the
local University's computer department, with a view to majoring in Computer
Science (which I did)).
--
Dave Horsfall DTM (VK2KFU) "Those who don't understand security will
suffer."
27 Mar
27 Mar
1:49 a.m.
On Wed, 22 Mar 2017, Ron Natalie wrote:
Ah yes, the machine with only 8 instructions (of
course not counting all
the multiplexing of OPR).
I was always fond of TAD. Not particularly reentrant version of
subroutine linkage.
Yep, it could add, but not subtract. Dammit, but I'm trying to think of
the CADET acronym; it went something like "Can't Add, Didn't Even
Try".
And as for subroutine calls on the -8, let's not go there... As I dimly
recall, it planted the return address into the first word of the called
routine and jumped to the second instruction; to return, you did an
indirect jump to the first word. Recursion? What was that?
Somewhere out there (tm), is a huge list of computer acronyms (and yes, I
know about "Instant Befuddled Mind", and "I've Been Misled"
etc).
--
Dave Horsfall DTM (VK2KFU) "Those who don't understand security will
suffer."
2:11 a.m.
On 3/26/17, Dave Horsfall <dave(a)horsfall.org> wrote [regarding the PDP-8]:
Yep, it could add, but not subtract. Dammit, but
I'm trying to think of
the CADET acronym; it went something like "Can't Add, Didn't Even
Try".
CADET was the official IBM internal development code name for the
1620, designed to be a low cost computer for the scientific
marketplace. Part of the reduced cost was attained by abandoning the
traditional ALU circuitry. Instead the 1620 did arithmetic by table
lookup. The joke was made that CADET stood for "Can't Add, Doesn't
Even Try", and that interpretation stuck and became popular with the
machine's user community.
-Paul W.
4:20 a.m.
On Sunday, 26 March 2017 at 16:11:30 -0400, Paul Winalski wrote:
On 3/26/17, Dave Horsfall <dave(a)horsfall.org>
wrote [regarding the PDP-8]:
I didn't know it was an official name of a project, and I thought it
referred to the 1401, the predecessor of the 1620. To be fair, they
did arithmetic one byte at a time, so a table lookup made sense.
Greg
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Yep, it could add, but not subtract. Dammit, but
I'm trying to think of
the CADET acronym; it went something like "Can't Add, Didn't Even
Try".
CADET was the official IBM internal development code name for the
1620, designed to be a low cost computer for the scientific
marketplace. Part of the reduced cost was attained by abandoning the
traditional ALU circuitry. Instead the 1620 did arithmetic by table
lookup. The joke was made that CADET stood for "Can't Add, Doesn't
Even Try", and that interpretation stuck and became popular with the
machine's user community.
4:25 a.m.
On Monday, 27 March 2017 at 6:49:30 +1100, Dave Horsfall wrote:
And as for subroutine calls on the -8, let's not go there... As I dimly
recall, it planted the return address into the first word of the called
routine and jumped to the second instruction; to return, you did an
indirect jump to the first word. Recursion? What was that?
This was fairly typical of the day. I've used other machines (UNIVAC,
Control Data) that did the same. Later models added a second call
method that stored the return address in a register instead, only
marginally easier for recursion.
At Uni I was given a relatively simple task to do in PDP-8 assembler:
a triple precision routine (36 bits!) to clip a value to ensure it
stayed between two limits. Simple, eh? Not on the PDP-8. Three
parameters, each three words long. only one register, no index
registers. I didn't finish it. Revisiting now, I still don't know
how to do it elegantly. How *did* the PDP-8 pass parameters?
Greg
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5 comments
4 participants
participants (4)
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Dave Horsfall -
Greg 'groggy' Lehey -
Paul Winalski -
Ron Natalie