🚀 go-pugleaf

On 23/07/18 13:04, Bob Eager wrote:
> On Mon, 23 Jul 2018 12:16:48 +0100, Brian Reay wrote:
> 
>> In the mid/late 70s, when I was at Uni, I had a vacation job and worked
>> on a project involving the 6100 uP.
>>
>> Initially, I was let loose on a simple singe board dev system (if you
>> can call it that), a simple keyboard, 7 segment display etc, as was
>> common at the time.
>>
>> Eventually, I was trusted to use a 'real computer' - laughable by
>> today's standards but ..... . It was a typical (at the time) 'Pizza Box'
>> 6100 based unit, I'm pretty sure it had toggle switches for data and
>> address set up etc but I used other machines around then and it was 40
>> years ago, the usual LEDs etc. I/O was teletype etc.- no CRT etc.  I'm
>> sure at the time, Intersil were the only make of the 6100 and probably
>> made the Pizza Box.
>>
>> Purely for old times sake, I'd like to try and acquire one- if the price
>> is right.
>>
>> Does anyone know the beast, please?
> 
> Yes, I do. Or, rather I have two of the 'second source' version, from
> Harris. The 6120, in fact, which was slightly enhanced.
> 

Interesting, I thought Harris bought out Intersil but perhaps not.

> You may know that the instruction set was that of the Digital Equipment
> Corp. PDP-8; a nice little, very successful minicomputer first announced
> on 28th May 1965. That used discrete logic, then later SSI TTL logic.
> They ended up with the 6100/6120.

I recall the Instruction set was the PDP one.
> 
> I have built two kits using the 6120, but I obtained the actual CPU chips
> as part of the kits, from someone who had acquired a limited supply. The
> kits are no longer available.
> 
> Here are both versions:
> 
>    http://www.bobeager.uk/projects.html#sbc6120
> 
> The panel is a near replica on an early model of the PDP-8.
> 
> You can't get the chip, but there is a PDP-8 simulator available for most
> platforms, which simulates the entire instruction set. Even better, there
> is a kit available (the PiDP-8) which is a scale model (physically) of a
> later version of the PDP-8. I have the kit, but no tuit yet!
> 
>   http://obsolescence.wixsite.com/obsolescence/pidp-8
> 
> Lots of software and resources available for the 6100/6120/PDP-8.
> 
> There is also a PiDP-11...I have that too.
> 
> The PDP-8 architecture is very simple. 12 bit word, with a 3 bit opcode
> field (i.e. 8 instructions!). TAD (add), DCA (store and clear
> accumulator), AND, JMP, JMS (subroutine call), ISZ (increment and skip if
> zero). Then an I/O group (IOT) and the operate group (instructions not
> needing an address).
> 
> The other 9 bits were a 7 bit address, a bit for indirection, and a bit
> setting the address 'page' (128 word block), either the current one of
> the zeroth one (rather like the 6502 years later).
> 
> The operate group used the address bits to specify microcoded actions.
> 
> Many resources, but here's an example.
> 
>   http://homepage.divms.uiowa.edu/~jones/pdp8/man/index.html
> 

Thank you, I will have a look.