Re: Smallest system you've ever worked on?

This was one of DEC's greatest lost opportunities. RT-11 was simple, fast and a joy to program under, like CPM and MS-DOS wanted to be, but never quite got to. By choosing a crippled version of RSX, then requiring you to use a DEC mini to write software, DEC managed exclude most of the young developers who were driving the PC revolution. I was at DEC then, and I think a lot of their bad decisions resulted from internal politics.

-- Jim McGinnis

A valid criticism. I've only gotten my mine to live for a few minutes.

Not really sure which was first there, but there were some similarities between the devices.

At that time 32 bit and VAX was were everybody was supposed to be going to and dropping PDP-11's as quickly as possible.

Then again Ken Olson had at least a PDP-11/03 at home and still said "No one needs a home computer".

Ditto..

Like a lot of companies at the time inward not outward looking. I left DEC in '83 and went onto other things.

Ken also famously called UNIX "snake oil". I would think at least half of the DEC machines at the time he said it were running UNIX. DEC seemed to be about half a decade behind when it came to software.

Digital PDP-11 was first. The resemblance of Motorola microprocessors and Digital minis is no accident: the original 6800 was as much of PDP-11 as the Motorola engineers could squeeze on silicon of that time.

Motorola was an active OEM user of Digital minis before they started their own microprocessor line.

The 68000 was a growth path from the 6800 root without looking at the common ancestor (PDP-11) or the cousin (VAXen).

Some of the more distant cousins include the Data General Nova / Eclipse line: it was created by some ex-Digital designers after their idea of PDP-11 was put on hold.

Having programmer/user experience of them all.

Tauno Voipio tauno voipio @ iki fi

Made one in the 70s using only sn7489's

Remove "HeadFromButt", before replying by email.

maxfoo wrote in news: snipped-for-privacy@4ax.com:

I was wondering just how much processing power would be needed to have a model mimic ALL the activities of a cockroach - including hard realtime requirement to avoid the rolled-up newspaper when the roach feels a breeze from its rapid descent. Oh, and wheels would be cheating - has to be able to run up walls and hang underneath decking ;)

What do you think? State machine and neural net in fpga? Or 3GHz processor? We can achieve a lot with tiny amounts of processing power in embedded systems, but we still have a long way to go before we can compete with the complex behaviour achieved by a couple of grams of bug mush.

I think you are missing the point. In those days, when we discovered a faulty dip chip, we placed it on the floor and executed it a la cockroach, with a ceremonial stomp. This prevented bean counters salvaging those valuable chips.

Even trying to stretch my imagination to the limit, I can not see any resemblance between 6800 and PDP-11. The 6800 with two accumulators and one index register would be similar to Nova or (Honeywell DDP-316/516). Perhaps some DEC 18 bit machines (such as PDP-15) might have had a similar architecture, but I have not used these 18 bit processors.

The 68000 is somewhere between PDP-11 and VAX, but the similarities between 6800 and 68000 are surprisingly few.

Paul

I'd have to agree. I've studied the instruction set and written assembly language for both, and I see almost no resmblance in philosophy, the general architecture or the layout of the instruction set.

The 68000 was more similar to the PDP-11 than the 6800 was, but the 68000 still differed in basic philosphy from the PDP-11.

The most obvious difference was the dedicated address/data registers in the 68K (which was more of an extension of the accumulator/index-register design in the 6800) verses the beautiful, orthogonal design of the PDP-11 where any register could be used for anything.

Wasn't it one of those that was the subject of "The Soul of a New Machine", the primal Silicon-Valley-burnout book?

Steve

TSoaNM was about the development of the Eclipse (a 32-bit virtual memory machine to compete with DEC's VAX line).

Silicon Valley?!?!? That's a bit insulting. Both DEC and DG were in Massachusetts. Ya know, those of us east of California have indoor plumbing and electricty and phones and TV and the internet and everything....

Ah, ok. Knew it was DG though ;).

Oops. I'm in the UK. You all look the same from here ;).

Steve

Actually, it was their idea of a 16-bit computer that they literally stole from DIGITAL. The PDP-11 was conceived AFTER they departed. - RM

Machine",

Not quite - there were the 16 bit Novas and Eclipses before the 32-bit virtual memory Eclipse the book tells about.

There are still on my bookshelf the manuals for the AOS/VS, the operating system for the 32-bit Eclipses.

Tauno Voipio tauno voipio @ iki fi

Right. The Nova was what was about to be the PDP-11, but it was held, as PDP-8's were still selling well, and that was not to be disturbed. The designers got frustrated, moved to neighboring town and started Data General.

Tauno Voipio tauno voipio @ iki fi

The AT9S1200 has 1kByte of codespace, this is only 512 words. The 1200 is very simular to the ATtiny11 but I think it no longer is in production. Or at least not recommended for new designs.

An operation similar to what Bob Pease calls "widlarizing," though with perhaps a different motivation. See

Regards,

-=Dave