New subject: Clever code

13 Dec 2022

...
  From: Stuff Received 
...
  I had always thought of a delay line as a precursor to
a register (or
 stack) for storing intermediate results. Is this not an accurate way of
 thinking about it? 
No, not at all.

First: delay lines were a memory _technology_ (one that was inherently
serial, not random-access). They preceded all others.

Second: registers used to have two aspects - one now gone (and maybe the
second too). The first was that the _technology_ used to implement them
(latches built out of tubes, then transistors) was faster than main memory -
a distinction now mostly gone, especially since caches blur the speed
distinction between today's main memory and registers. The second was that
registers, being smaller in numbers, could be named with a few bits, allowing
them to be named with a small share of the bits in an instruction. (This one
still remains, although instructions are now so long it's probably less
important.)

Some delay-line machines had two different delay line sizes (since size is
equivalent to average access time) - what one might consider 'registers' were
kept in the small ones, for fast access at all times, whereas main memory
used the longer ones.

	Noel

Re: Clever code