🚀 go-pugleaf

>One interesting thing about the DEC 20 (and I guess DEC 10 and
>pdp-6 as well) is that the registers are the first 8 or 16 locations in the
>main memory map.  Does anyone know if code can be run in the registers?  And
>if so, does it execute any faster than if it was in normal memory?

Yes, it could be done and it was considerably faster at least in the older
DEC-10 models.  I remember reading that a separate register set was not an
essential part of the architecture --- if it was removed, the first 16 words
of the main memory were used instead and the machine still functioned
correctly, only more slowly.
--
Matti Jokinen