kens
I'd suggest the Datapoint 2200 as the most influential
minicomputer of all time since half of you are using an
instruction set based on it and it is largely responsible
for the creation of the microprocessor.Now mostly
forgotten, the Datapoint 2200 was a programmable desktop
computer introduced in 1970. It had a processor built from
TTL chips, along with shift-register memory from Intel.
Datapoint discussed with Intel and Texas Instruments the
possibility of building a single-chip processor to replace
the board of TTL chips. TI was first with the TMX 1795
processor, followed by Intel's 8008, both copying the
Datapoint 2200 instruction set.Datapoint decided that
these chips didn't have enough performance and fatefully
gave up rights to them. TI tried to sell the TMX 1795 to
Ford, but got nowhere and abandoned the chip. Intel
decided to sell the 8008 as a standalong microprocessor,
which was used in early personal computers like the
Mark-8. Intel improved the 8008 to form the 8080, then
made a somewhat compatible 16-bit version, the 8086, which
started the x86 architecture. (Because the Datapoint 2200
was little-endian (to use shift-register memory), x86 is
little-endian.)To summarize its influence, without the
Datapoint 2200, the microcomputer industry would have been
greatly delayed (since the 4004 wasn't suitable for a
personal computer) and x86 wouldn't exist.
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> smallstepforman
The 6809 (and its clone the 6502) would also be strong
contendors. And if Motorola were 6 months faster with
the successor 68000 compared to Intels 8086, the IBM
PC would be 68000 based and Intel would today be known
as a memory chip company. We'd be big endian with no
legacy in 2026 of segmented memory architecture in
mainstream processors. And with big 3 companies using
68000 (IBM, Apple and C=), we definately wouldnt have
WinTel.
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> > rswail
That was the 1980s, PDP-11s were the 1970s.
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> > > mrandish
The influence was what the people who learned
computing in the 70s on PDP-11s at university,
went on to do with what they'd learned in the
80s.Also, the 6809 shipped in 1978. Little
known fact, the Macintosh was going to be
based on the 6809 and Jef Raskin's team had
6809 Mac prototypes running before Steve got
Motorola to drop their price on the 68000 (in
part because Moto was panicked over losing out
on the PC).
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> > > > rswail
Agreed, just saying that the PDPs were
where a lot of the people developing micro
computers cut their teeth eg CP/M looks a
lot like RT-11.Minicomputers like the
PDP-11 begat microcomputers around 8080s,
Z80s, 6509s, 6502s."Home" microcomputers
started around 1977/78 with the Apple ][
and TRS-80 and PET.
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> > > > > mrandish
For sure, by volume the impact of the
PDP-11 was almost entirely through
micros and workstations because they
were taking over so fast. Although,
Unix and C did spread like wildfire
from the PDP-11 to other minis. In
fact, C was originally created for
porting Unix.In terms of timing, the
PDP-11 shipped in early 1970 and was
an immediate best-seller. Back then,
students didn't get much hands-on
computer time until their final two
years so by the mid-70s its influence
was already being felt. The 6809 was
being designed in 1975 and the
architecture was clearly inspired by
the PDP-11's orthogonal ISA,
interrupts stack handling, etc.
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> > classichasclass
The 6502 isn't a 6809 clone; it was largely
inspired by the 6800.
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> > > smallstepforman
My mistake. I remember reading the C= book "on
the edge" and there was a chapter about how 3
chip designers at motorola couldnt get
management to pursue low cost version of 6800,
so they made 6502 in a startup called MOS in
1975.
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> > smallstepforman
While I'm on alternative histories, if Jack
Tramiel didn't piss off Chuck Peddle, it would be
MOS/C= in Intels pisition today.
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> chasil
What is not well-known is that:a) the PDP-11 CPU was
also implemented in TTL logic, like the Datapoint,b)
there were later implementations of the PDP-11 as NMOS
microprocessors:https://en.wikipedia.org/wiki/DEC_T-11
https://en.wikipedia.org/wiki/PDP-11#LSI-11_integrated
_circu...c) the VT100 terminal was based on the Intel
8080
microprocessorhttps://en.wikipedia.org/wiki/VT100There
was appreciation and exchange between Intel and DEC.
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> HarHarVeryFunny
Apparently Motorola had started work on their PDP 11
inspired 6800 in 1971, same year the Datapoint 2200
terminal was released, and would end up shipping it in
1974, same year Intel released their 8008 successor
the 8080 (which the Altair 8800 was based on), so even
without Intel's calculator (4004) and terminal (8008)
chips we'd still have had single-chip LSI CPUs in a
similar time frame.
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> throwaway27448
You can see the influence of the PDP-11 on C more than
any other ISA. That alone I think qualifies it as the
most influential microprocessor of all time.
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> themafia
The Internet (mostly), the C language, the Unix
Operating System were all developed and deployed on
PDPs. The BASIC language /and/ an 8080 emulator was
developed on a PDP in order to deploy to the Altair.I
would argue that Intel was so highly influenced by
Datapoint due to sheer proximity and early
inexperience in the field.
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> > kens
I don't think you can count PDP-10 things
(Internet, BASIC, 8080 emulator) to support the
influence of the PDP-11, since they were
completely different computers. The PDP-10 was a
36-bit mainframe, while the PDP-11 was a 16-bit
minicomputer.
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> > > phire
PDP's lack of naming really confuses things,
they essentially just numbered the computers
by release date.There are like 3-5 completely
different family trees of computers in their
numbering scheme (depending on how you count),
all of them are notable in some way.
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> > > > cesaref
Yeah, there were two busses, and the
bigger ones were certainly rather
impressive. I built a PDP-11/23 out of
spare bits gifted from a university
physics department in the late 80s, and it
was awesome, but nothing like an 11/70 or
anything like that!
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> > > mrandish
While I just missed out on minis and
mainframes (starting with early 8-bit micros
and 4k RAM), as a retro fan who's read deep
into the Datapoint 2200, Intel, TI saga, I
agree the DataPoint is a heavy hitter easily
deserving of the title. But measuring 'most
influential' is tricky because it depends on
whether we use a hardware or software
yardstick. For hardware, the Datapoint is a
slam dunk for its influence on, arguably, the
first 8-bit CPU (8008) and its eventual DNA
impact on the CPU gene pool (x86).For
software, the PDP-11 has an ironclad claim on
operating systems (Unix - which gestated on
the PDP-7 but was born on the PDP-11) and
languages (C), with a strong 2nd place in
hardware via its heavy influence on the
venerable Motorola 68000 family.I also agree
the PDP-10 should be part of this conversation
as it was certainly influential. My
second-hand sense from reading retro history,
is the PDP-10 was beloved, if not revered, by
nearly all who touched it. It was indeed an
aspirational North star, but its eventual
influence was both delayed and limited.
Limited because it was a monstrously powerful
mainframe with an equally monstrous price,
selling only 1,500 units compared to the
PDP-11's 600,000. This limited those who saw
it to major research institutions (MIT,
Stanford, etc) and large corporations. And
delayed because the PDP-10's incredible power
allowed some futuristic concepts to be
experimentally prototyped on it first, but the
advanced operating system and networking ideas
pioneered on the PDP-10 would have to wait for
32-bit power to arrive on desktops in the late
80s and 90s.Personally, I give the nod to the
PDP-11 for biased (but justified) reasons.
Everyone in 80s computing knew of the PDP-11,
whereas I was already a retro collector before
I'd ever heard of the Datapoint and its valid
claims to the title (and I still can't name
its operating system or any languages and
applications born on it). Unfair... but is
history is rarely fair. And in any dead-even
tie, whatever side x86 is on must lose
because, to me, it will forever bear the
WinTel beige stain of being the asteroid that
snuffed out a Cambrian explosion of diverse
platforms, OSes and apps in the late 80s to
mid-90s.
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> > larsbrinkhoff
BASIC was developed on GE mainframes.
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rswail
My first ever computing experience was in 1977 in year 9
at high school where we were lucky enough to have a
PDP-11/10 with 16K(!) and 3 ASR-33s and a VT-52.Learned
how to program in octal on the front panel. I've still got
an old front panel (the rest is a rotting collection of
wirewrap boards in my garage).It had a multi-user basic
that left out string functions if you went multi-user. You
loaded the bootstrap via the front panel, which read the
"absolute loader" from paper tape on one of the TTYs,
which then read the BASIC interpreter from the same
source.I still have the small reference card with the
instruction set and some old paper tapes around
somewhere.The whole structure of the registers with R7 as
the PC and R6 as the SP and the various addressing modes
was just elegant.We used to make jokes that your
programmed a PDP-11 with 3 fingers (octal) and a VAX with
4 (hex).
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allenrb
I'm not quite old enough to have grown up with the PDP-11.
They were gone from university (or at least the parts I
had access to) by the time I arrived. But I did see
exactly one in the wild.In 1997-1998, I was working for a
small company in Atlanta who did tape backup systems. At a
client in maybe Knoxville (?), a hospital had a PDP-11/70
live in their machine room. Amusingly, right next to racks
of then super-fancy Cisco gigabit fiber networking.I was
told that the PDP handled payroll. Guess that was
important. Wonder how long it lasted there?
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> hylaride
PDP-11s and their VAX successors could often still be
seen in hospitals as late as the mid 2000s as the back
ends to all sorts of expensive equipment (MRIs, etc).
At the time I was told that rewriting the medical code
was one of those "not worth the risk" endeavours. By
now they've probably been virtualized away, but those
machines were damned reliable.
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> hcfman
Oh man. You are really missing out unless you started
with valves and watched transistors come out as the
cool kid on the block.To see all that and still be
programming now is one very lucky journey.
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ggm
I'd argue the pdp8 opened the floodgates. That's when the
cost of digital computing dropped to the point a research
grant or even just discretionary spending in a university
department could pay for one, and you didn't need a
special room and power supply.the 11 was when it became
more useful. But the 8 was how people realised you could
move beyond a calculator to a computer.
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> ErroneousBosh
> That's when the cost of digital computing dropped to
the point a research grant or even just discretionary
spending in a university department could pay for
oneI've mentioned this before, but the PDP8 launched
in the US about the same time as JCB launched their
first (and arguably the first really practical and
useful) backhoe loader in the UK, which was about
three and a half grand at the time.Can you imagine the
paradigm shift with either of those machines? Not just
it's possible to do that work, but you can do that
work with *your own one*.At some point someone has
looked at a shiny new PDP8 or a JCB 3C in the showroom
and gone "you know what, I'm just going to buy one",
and got the chequebook out.
|
> > ggm
That's an amazing parallel. So much to think about
how it changed dynamics of work replacing manual
ditch digging and wheelbarrows.
|
> larsbrinkhoff
Then maybe also give a nod to the LINC, showing DEC a
small 12-bit computer could be made.
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JKCalhoun
Obsolescence Guaranteed makes a PDP-11 replica [1]. At the
heart is a Raspberry Pi running emulation software. All
switches, LEDs are physical-all wrapped up in a clever
case that looks like the original.I have bought a couple
of their kits and can vouch for the quality of them.[1]
https://obsolescence.dev/pdp11.html
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not2b
It was the preferred lab computer in the mid to late 1970s
and into the 80s. I got my first job because I knew PDP-11
assembly language, and worked with both DEC's operating
systems for them (RT-11 and RSX-11) and later Unix (the
lab I worked with had some machines running Version 6,
though Version 7 was the first that I used seriously. It
had a very clean and symmetric instruction set that used
the program counter as if it were another general purpose
register. I had an LSI-11 board (the single-board version
of the machine) with 4K 16-bit words of core memory and a
paper tape punch with a tiny loader in ROM to read in the
tape and peek and poke memory, and I'd sometimes
initialize the core memory to a known state by running the
one-instruction programmov -(pc), -(pc)
or 014747 in octal. It would fill all of memory with
014747.
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> amirhirsch
014747 makes me smile <3I built the PDP-11/70 emulator
that controls the nuclear reactors in Ontario. That
was 20 years ago and I'm probably still the youngest
person who can read PDP-11 assembly (and the raw
octal)
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> > ErroneousBosh
There's a decent chance you're younger than me,
but I can still read it. Coincidentally about 20
years ago I got asked to fix a bug in some PDP11
code that ran on real hardware because it was
tripping up an emulated system. Nothing wrong with
the emulator as such, it was just a logic bug in
the program that they no longer wanted to work
around.I made the fateful mistake of saying "Sure,
sounds fun, how hard could it possibly be...?"
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> > > le-mark
Not pdp-11 but once I was tasked with fixing a
c program the offshore team had failed to fix
for over a year. I basically took a month off
(at my desk) after I fixed it the first day.
They were happy, I was a legend at that
company!
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> > > amirhirsch
Love your handleThe FPGA emulator we made had
to pass the xxdp test suite which was provided
to me on punched tape and microfiche. The
emulator had a specific test for FDIV overflow
which even tested the accuracy of the partial
result. None of the software emulators I
tested did this. I emailed Gordon Bell who
introduced me to Bob Supnkk, and we found the
original flowcharts for it so I could
replicate the divider logic precisely. Imagine
a nuclear reactor dependent on this lol.
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> mrandish
> It had a very clean and symmetric instruction
setIndeed. Motorola's 68000 CPU took so much
inspiration from the PDP-11's ISA, it was almost a
spiritual successor. The 68000's 8/16-bit little
brother, the 6809, widely considered the most powerful
8-bit CPU ever - was also heavily inspired by the
PDP-11.
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> > tralarpa
Somes lines in PDP-11 assembly from 2.11BSD: mov
r1,-(sp)
mov $1024.,-(sp)
mov $outbuf,-(sp)
mov fout,-(sp)
jsr pc,_write
add $6,sp
mov (sp)+,r1
tst r0
bpl 2f
jmp wrterr
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> getpost
Ha! The instruction that copies itself. I posted also
posted it, 6 years ago.
https://news.ycombinator.com/item?id=24820583
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EvanAnderson
There's a parallel worldline out there where the PDP-11
made the transition into a desktop PC[0] and the IBM PC
didn't take over the world. In that worldline our servers
are from the PDP-11 lineage, and not the IBM PC.[0]
https://en.wikipedia.org/wiki/DEC_Professional_(computer)
|
> classichasclass
I've got a DEC Pro 380 myself (
https://oldvcr.blogspot.com/2025/03/more-pro-for-dec-p
rofess... ). It's a heck of a desktop computer, and
you can run some early Unices on them. The Pro and the
DECmate II are some of the best built systems of the
era despite their idiosyncrasies, IMHO.
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aitoh
The computers that ran Unix were DEC's (Digital Equipment
Corporation) PDP-11 machines. Just then, DEC's Japanese
subsidiary (DEC Japan) was holding its first-ever
recruitment of new graduates, and in 1980 I was fortunate
enough to be hired.After joining, however, I ran into one
astonishing fact. DEC, then a hardware manufacturer, fully
supported its own operating systems (RSX-11, VMS, and the
like), but for Unix - a licensed product of Bell Labs
(AT&T) - it offered no official service or technical
support whatsoever. (It would be added to the official
service menu in later years, but in 1980 it was out of
scope.) I had joined a manufacturer in order to make Unix
my work, only to find that the manufacturer did not
support Unix - a historical gap that left me bewildered at
the time.
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WalterBright
I had a PDP-11, in the form of the Heathkit H-11.I loved
that computer. Like a fool, I sold it for $25. There's a
picture of it on my X profile.The -11 had an instruction
set that fit on one page.
|
> wduquette
Yes, that's what we had too. I loved that machine.
What was the incantation? 104799L, or something like
that?
|
> jakzurr
ok, that's amazing - glad ya saved the pic at least
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budman1
+1 to pdp11.
The workhorse of the 1970's.
They were everywhere. City Library. Auto parts stores.
And reliable; Maytag ain't got nothing on a pdp
11.Downside, programs are pretty simple that run in 64k.
And extended addressing in any form, sucks.
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wduquette
Heathkit sold an LSI-11 as a kit; my father built one in
the mid-70's. I learned BASIC, a bit of Fortran, a bit of
PDP-11 assembler, and Pascal on that machine. We started
with paper type, and eventually moved up to dual 8"
floppies. We started with 16K of memory, IIRC, and ended
with 28K.Been a programmer ever since, me.
|
jakzurr
Used several of these at school in the 90's. IIRC intro
classes used VAX/VMS (was the machine called VAX-1170?).
But all the higher undergrad classes used Unix on
PDP-11/70's, like in the picture. Of course, I hardly ever
saw one up close. :p
|
> jakzurr
thank god we weren't still using paper tape & punch
cards, everything was old crt terminals, and online
storage (though not very much)
|
gerdesj
"PDP-11 with UNIX opened the floodgates for inexpensive
interactive computing, which then led to an explosion of
office productivity. "Well before we get too misty eyed:
"inexpensive" needs looking at "for inexpensive
interactive computing".I'm not old (55) enough to have
really got to grips with a PDP11. I do still own (yes:
present tense) a C64 from 1986. The C64 was bought by my
dad via the NAAFI in West Germany so I have no idea what
it costed. Let's wind forward a bit:I had a 80286 based PC
in 1987ish with 1MB of RAM, 20MB RLL hard disc. The
graphics card (ISA) had a whopping 512 bytes of RAM. That
thing costed about £1200. I added a 80287 later at about
£120 so I could run a pirated copy of AutoCAD.In 1990ish
I had a 80486 with 4Mb RAM and 40MB HD - that costed
something like £1600.Nowadays £1600 will buy quite a
decent laptop and 35 years of inflation.
|
> pezezin
> The graphics card (ISA) had a whopping 512 bytes of
RAM.I think you are missing a "kilo" there...
|
> > gerdesj
The k key on my laptop is a bit shagged. I've just
hit it harder twice.
|
TomMasz
Back in my running days in the 80s, the people who did the
timing and race results had a van with a PDP-11 in it that
I assume ran off a generator. I wish I had asked them more
about it but I was too busy worrying about running.
|
TradingPlaces
My high school had one of them in the early 80s. Me and a
few others were the only ones who ever turned it on. Then
a friend got an Apple ][ and we never touched the PDP-11
again.
|
nickcw
I'm not old enough to have used a PDP-11 so I read through
the assembly code description with interest.Wow, it seems
so modern. I've used a lot of assembly languages over the
years but I'd feel immediately at home here. Nice sensible
orthogonal instruction set with enough registers and a
stack pointer. It reminded me immediately of ARM assembly
- what a breath of fresh air that was when it came it.I
never realised quite how much influence the PDP-11 had on
computer architecture. I knew about it's software legacy
but I suspect that was enabled by it's ground breaking
architecture.
|
> mrandish
My first computer had a 6809 with 4K of RAM and I
learned assembler on that 6809, which was greatly
inspired by the PDP-11 architecture. My second
computer was an Amiga 1000 with a 68000, a CPU even
more directly a successor to the PDP-11 than any
other. As far as I knew, those two PDP-11-like systems
were computer architecture. Orthogonal instruction
sets, user and system stacks treated just like any
other register, layered interrupts, indirect
addressing, memory mapped I/O,
auto-increment/decrement, relocatable zero page,
contiguous flat memory map, relative addressing that
made position-independent, re-entrant code trivially
easy. Yeah, in the 1980s, I led a sheltered, happy
computing life.It was around the mid-90s by the time I
tried x86 assembler. I don't think "shocked" quite
captures the experience. It was more like disbelief,
then something akin to abject horror, which finally
just faded into creeping existential dread. Before the
X86, I loved coding in assembler but the nicest thing
I can say about x86, is it motivated me to learn C as
fast as possible. :-)
|
PopePompus
What happened if you used auto-decrement addressing with
the PC? Did that hang the computer?
|
> Taniwha
Yup, as mentioned above the famous:x: mov -(pc),
-(pc)reads an instruction from x, increments the PC to
x+2, then decrements the PC back to x and reads the
same instruction, then decrements it again to x-2 and
writes it, then it executes from x-2 ......
|
ubermonkey
There's a concept in history whose name escapes me, but
which was evoked often when Harrison Tyler died in 2025.
Tyler was a private citizen, but he was of note because he
was the grandson of the US's 10th president John Tyler --
who died in 1862.The gist is how surprising bridges to the
past are closer than you realize -- as is the past
itself.At my first corporate job in 1994, we had a machine
room. Those weren't uncommon back then. What WAS uncommon
was that, over in a corner, sandwiched between racks of
shiny new DEC Alphas, was a PDP-11 that was still running
production code.My employer then was TeleCheck, which did
point of sale risk analysis for checks. The business had
originally been run as independent state-by-state
franchises, and back then someone had the bright idea to
create an IT company that provided services to these
franchisees -- and, occasionally, to other companies, too.
By the time I was hired, the franchises AND the IT company
had all been brought under one ownership, and all the IT
company's external clients had gone elsewhere EXCEPT
ONE.That holdout was perfectly happy with what they got
from that ancient computer.I assume it eventually died,
but TeleCheck had a DEEP bench of DEC talent, so it
could've kept running a long, long time.
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