1 Dec
2021
1 Dec
'21
11 a.m.
Henry Bent writes:
On Tue, 30 Nov 2021 at 18:10, Jon Steinhart
<jon(a)fourwinds.com> wrote:
Sorry my analogy didn't work. Look at a photomicrograph of a chip; at least
to me it's pretty obvious where the random logic is located.
Here's another try. In a microcoded machine, the same hardware is used for
every microinstruction. In random logic, custom designed circuitry is used
for each special case.
Humm writes:
OK, I'll try again. For anybody familiar with Portland, Oregon, it's the
difference between driving in Northwest where there's a rectangular grid
numbered in one direction and alphabetical in the other, and approaching
the Ross Island Bridge from the west side which appears to be designed by
someone following a goat while tripping their brains out. One can address
Northwest Portland quite easily unlike getting onto the Ross Island Bridge.
So - and as I say this as someone who has no direct experience with this
level of logic - everything is directly addressable but the difference is
in how you get there? Quoth Jon Steinhart:
>arnold(a)skeeve.com writes:
>> Can someone please explain why it's called "random" logic?
Discrete
>> logic I understand (more or less), but I've not heard the term
"random"
> used
in this context before now.
Well, as a recovered random logic designer, I think that the name comes
from there being no particular structure to the logic. Many parts of
logic design are very regular, think memory. But that regularity doesn't
exist when, for example, decoding irregular instructions.
Now that's a "random" definition.
--
Humm