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.
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 microprocessor
https://en.wikipedia.org/wiki/VT100
There was appreciation and exchange between Intel and DEC.
I would argue that Intel was so highly influenced by Datapoint due to sheer proximity and early inexperience in the field.
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).
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?
To see all that and still be programming now is one very lucky journey.
the 11 was when it became more useful. But the 8 was how people realised you could move beyond a calculator to a computer.
I'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.
I have bought a couple of their kits and can vouch for the quality of them.
mov -(pc), -(pc) or 014747 in octal. It would fill all of memory with 014747.
I 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)
I made the fateful mistake of saying "Sure, sounds fun, how hard could it possibly be...?"
Indeed. 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.
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[0] https://en.wikipedia.org/wiki/DEC_Professional_(computer)
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.
Downside, programs are pretty simple that run in 64k. And extended addressing in any form, sucks.
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.
Been a programmer ever since, me.
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.
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.
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. :-)
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.
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 ......
The 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.
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.
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.
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).
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.
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.