LISP implementations on small machines

[Guy Sotomayor Jr]

> On Oct 3, 2019, at 10:26 AM, Paul Koning via cctalk <cctalk at classiccmp.org> wrote:
> 
> 
> 
>> On Oct 3, 2019, at 12:39 PM, Chuck Guzis via cctalk <cctalk at classiccmp.org> wrote:
>> 
>> On 10/3/19 9:01 AM, Noel Chiappa via cctalk wrote:
>> 
>>> The PDP-6 and KA10 (basically a re-implementation of the PDP-6 architecture)
>>> both had cheapo versions where addresses 0-15 were in main memory, but also
>>> had an option for real registers, e.g. in the PDP-6: "The Type 162 Fast
>>> Memory Module contains 16 words with a 0.4 usecond cycle." The KA10 has
>>> a similar "fast memory option".
>> 
>> A bit more contemporary example might be the low-end PIC
>> microcontrollers (e.g. the 12F series).   Harvard architecture (14 bit
>> instructions, 8 bit data), but data is variously described as
>> "registers" (when used an instruction operand) or "memory" when
>> addressed indirectly.   That is, the 64 bytes of SRAM can be referred to
>> as either a memory location or as a register operand.
> 
> Then again, the PDP-10 has that "two ways to refer to it" as well.  In that case, you do have dedicated register logic, and what happens is that memory addresses 0-15 are instead redirected to the register array.  The same applies to the EL-X8.  The way you can address things doesn't necessarily tell you what sort of storage mechanism is used for it.
> 

So does the PDP-11.  The 8 registers are mapped to the top 8 words of memory so you can do some quite interesting things.  It is also possible to run a (small) program in only the registers (e.g. no memory at all).

TTFN - Guy