6502.org

Somewhat off topic, because although I did see a huge number of different 8-bit systems, I spent loads of time talking to Peter Onion, curator of the Elliott 803 which is an early British mainframe. He's got full logic diagrams for the machine and was extraordinarily helpful and knowledgeable.

One point of note: the integer multiplier is Booth-encoded, although it wasn't crystal clear whether it looks at 2 bits or 3 bits. It seems that it doesn't manage to halve the number of operations (which surprised me) but it does allow a signed multiplier to do an early-exit when it runs out of bits of interest. Might need more investigation to understand that. (Relates to this discussion here.)

My notes on the Elliott 803 here.
Many shakey and fuzzy pictures of 8bit and other computers here.

TNMOC is embedded in Bletchley Park, so I have other posts from the day:
- Turing, Enigma and the Bombe
- Tunny, Heath Robinson and Colossus
- U-110 and homing pigeons

I thoroughly recommend a day on site to anyone who finds themselves in the UK (it's a short train ride from London) - the main ticket is also an annual season ticket, and this is my third visit. I've never managed to get back within 12 months, but as you see, I find it worth multiple trips.

Cheers
Ed

p.s. some notes on the compiler, assembler, runtime and the boot loader can be found here.

p.p.s. some notes on magnetic core memory here, and on core-based logic here.

p.p.p.s. a description of the Elliott 803 microarchitecture and instruction set can be found in patent number RE28221

p.p.p.p.s there's an emulator by Tim Baldwin here.

Thanks for this, Ed. Lots of interesting material!
Following the link for core-based logic led me to the following paragraph (my empahasis added) and another excellent link (pdf of the Turing Award lecture):

"Forever associated with the Elliott 803 and its Algol system was a young classics graduate by the name of Hoare employed by Elliotts as a programmer in August 1960. Computer programming was then in its infancy and programmers were only beginning to understand the enormous complexities which it opened up. Hoare's early grasp of some of the principles of managing this complexity, in part due to managing his own disaster in the 503 operating system, enabled him to go on to dominate many aspects of Computer Science. Hoare recounts some of his experiences at Elliotts in the 1980 ACM Turing Award lecture (about 900kb) (The Emperor's Old Clothes, Com.ACM 24 2 Feb 1981)."

-- Jeff

Thanks for that link!

Edit: here's a gem on the Algol60 compiler: "every occurrence of every subscript of every subscripted variable was on every occasion checked at run time against both the upper and the lower declared bounds of the array. Many years later we asked our customers whether they wished us to provide an option to switch off these checks in the interests of efficiency on production runs. Unanimously, they urged us not to--they already knew how frequently subscript errors occur on production runs where failure to detect them could be disastrous."

Peter has shared a scan of an original doc here: http://www.peteronion.org.uk/803logic/cores.pdf (there are other interesting materials in that directory too.)

Gosh - I've just learnt "Iann Barron, the inventor of the transputer, designed the Elliott 803 and 503."
See here.

Edit: in a previous thread Michael notes that the early NOVA machines from Data General were also serial. See http://en.wikipedia.org/wiki/Data_Gener ... sor_design where it says "The earliest models of the Nova processed math serially in 4-bit packets, using a single 74181 bitslice ALU."

I saw an exhibition of the Milton Keynes museum at Brighton and I had a chance to see and touch a PDP-8!

Was that the Brighton mini-Maker faire?
http://www.makerfairebrighton.com/maker ... computing/

The maker movement, and the hackerspace movement, are both very encouraging.

Peter Onion has just released a block diagram of the Elliott 803 serial CPU:
http://www.peteronion.org.uk/803logic/8 ... agram2.jpg
(via http://twitter.com/PeterOnion/statuses/ ... 3736903680 which also says "Emulator for Raspberry Pi coming soon")

That's cool.

Just learnt that DEC at one point made a serial version of the PDP-8:
http://corestore.org/8s.htm
(lower price, lower performance: not a success: "A PDP-8/S is one-fifteenth of a PDP-8 at one-half the cost.")

I used to have a PDP-8 data book. Came in handy when we had to program a IMS 6100 (PDP-8 on a chip) single board computers at university.