Re: The "Good" Old Days - Complete Specs for DX-10 Operating System

In comp.os.linux.misc 186282@ud0s4.net <186283@ud0s4.net> wrote:

The 990 series used the TMS-9900 chip and near variants.  This was an
odd chip - kept the CPU registers out in ordinary RAM and could
switch quickly between different sets of registers.  At that time,
the external RAM and CPU kinda ran at the same speed so little was
lost putting the registers in RAM.

The 6502 did something similar.  It wasn't as far down the path as the
TI chip, but page zero (first 256 bytes of ram) acted a lot like an
'extended register file'.  There were even addressing modes that used
two consecutive bytes of "page zero" as a 16bit pointer into the rest
of the RAM one's system had installed,