Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

A brief tour of the PDP-11, the most influential minicomputer of all time (2022)

arstechnica.com

Post reply on HN
Print view View original

21–30 of 59 posts

Re: A brief tour of the PDP-11, the most influential minicomputer of all time (2022)

#21

Post by smallstepforman »

smallstepforman wrote: post #20
kens wrote: post #3

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 Int…

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 woul…

While I’m on alternative histories, if Jack Tramiel didn’t piss off Chuck Peddle, it would be MOS/C= in Intels pisition today.

Re: A brief tour of the PDP-11, the most influential minicomputer of all time (2022)

#22

Post by 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).

Re: A brief tour of the PDP-11, the most influential minicomputer of all time (2022)

#23

Post by rswail »

smallstepforman wrote: post #20
kens wrote: post #3

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 Int…

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 woul…

That was the 1980s, PDP-11s were the 1970s.

Re: A brief tour of the PDP-11, the most influential minicomputer of all time (2022)

#24

Post by mrandish »

kens wrote: post #10
themafia wrote: post #7

Earlier quoted context omitted.

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.

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.

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.

Re: A brief tour of the PDP-11, the most influential minicomputer of all time (2022)

#25

Post by pezezin »

gerdesj wrote: post #2

"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…

> The graphics card (ISA) had a whopping 512 bytes of RAM.

I think you are missing a "kilo" there...

Re: A brief tour of the PDP-11, the most influential minicomputer of all time (2022)

#26

Post by mrandish »

rswail wrote: post #23
smallstepforman wrote: post #20

Earlier quoted context omitted.

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 woul…

That was the 1980s, PDP-11s were the 1970s.

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).

Re: A brief tour of the PDP-11, the most influential minicomputer of all time (2022)

#27

Post by ggm »

ErroneousBosh wrote: post #17
ggm wrote: post #12

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.

> 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 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 th…

That's an amazing parallel. So much to think about how it changed dynamics of work replacing manual ditch digging and wheelbarrows.

Re: A brief tour of the PDP-11, the most influential minicomputer of all time (2022)

#28

Post by 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.

Re: A brief tour of the PDP-11, the most influential minicomputer of all time (2022)

#29

Post by rswail »

mrandish wrote: post #26
rswail wrote: post #23

Earlier quoted context omitted.

That was the 1980s, PDP-11s were the 1970s.

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).

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.

Re: A brief tour of the PDP-11, the most influential minicomputer of all time (2022)

#30

Post by tralarpa »

mrandish wrote: post #14
not2b wrote: post #9

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 a…

> It had a very clean and symmetric instruction set 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.

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
Post reply on HN