PDP-12 at the RICM

Johnny Billquist bqt at update.uu.se
Mon Jul 13 19:52:31 CDT 2015

On 2015-07-13 21:16, Rich Alderson wrote:
> From: Kip Koon
> Sent: Sunday, July 12, 2015 10:52 PM
>> I would be most interested in finding out more about this effort.  Do you have
>> ongoing pictures documenting this effort?  I'd love to have a PDP 8, 11, 12
>> someday, but I don't have the space for something like that much less the cost
>> involved so I'll have to be satisfied with emulators on my PC or eventually
>> building one or more of these systems with current technology like the SBC6120
>> if memory serves.  Are there other possible alternatives?  I used a PDP-8/E in
>> high school and college and have been quite interested in the high capability
>> PDPs like the PDP-11 Series for starters.  I didn't know there were PDP 12
>> Series computers.  Are there other PDP series computers as well?
> Don't confuse higher numbers with higher capabilities, or even as being related
> to each other.  DEC created computers with 9 different architectures before the
> 32-bit VAX was even dreamed of.
> The list of Programmed Data Processors goes like this:
> PDP-1	18-bit word, 12-bit address
> PDP-2	24-bit word, paper design only
> PDP-3	36-bit word, paper design only
> PDP-4	18-bit word, 13-bit address

You could argue that the PDP-4 is the successor to the PDP-1. Unless I 
remember wrong, it could run PDP-1 programs.

> PDP-5	12-bit word
> PDP-6	36-bit word, mainframe unrelated to PDP-3
> PDP-7	18-bit word, PDP-4 successor
> PDP-8	12-bit word, PDP-5 successor

12, 15 or 17 bit address. Depending on what hardware you have. Most 
typical was/is 15-bit address space.

> PDP-9	18-bit word, PDP-7 successor
> PDP-10	36-bit word, PDP-6 successor mainframe
> PDP-11	16-bit word, 16-bit address[2]
> PDP-12	12-bit word, PDP-8/i + LINC hybrid
> PDP-14	control processor for customer-built special purpose equipment
> PDP-15	18-bit word, PDP-9 successor
> PDP-16	Register-Transfer Module hard-wired processor, PDP-14 competitor[3]
> There were later variants of some of these:
> PDP-7A
> PDP-8/s, PDP-8/i & /l, PDP-8/e & /f & /m, PDP-8/A
> PDP-9/L
> PDP-15/76
> After 1971, they stopped naming things "PDP-n", with the exception of models of
> the PDP-11 (which eventually consisted of more than 20 models designated
> PDP-11/nn), but even there the Pro-3x0 desktop systems were called something
> else.  Later models were microprocessor-based.
> The later PDP-10 models were designated DECsystem-10 and DECSYSTEM-20.
> The later PDP-8 models were the DECmate, DECmate II, and DECmate III (word
> processing desktop systems) and the VT-78, all based on Intersil or Harris
> microprocessors which were roughly the PDP-8/e in silicon.
> "high capability PDPs" = PDP-10 & follow-ons.  PDP-11?  Pfeh.

As always, it depends on what people mean by "high capability". The 
PDP-10 were undeniably physically larger, and had a much larger address 
space. But they weren't exactly fast...

> [1] 1 built by a customer, reputed to be an NSA front company.

You forgot the actual anchor in the text. This relates to the PDP-3.

> [2] With memory management, 18 or 22, in 16-bit segments.  Late models could
>      use separate instruction and data segments, for a total of 128KB in use at
>      one time.

??? What segments??? The PDP-11 have a plain simple page table. No 
segments anywhere in sight. And each page is 8K.

You obviously need more exposure to PDP-11s, Rich. ;-)


Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

More information about the cctalk mailing list