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

On 02/10/2024 17:43, Rich wrote:

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,

The 6502 was an excellent little beast. I never programmed one myself, but I know people who did,  and my friend who worked on the original Acorn machines said it was pretty fast compared with a Z80 etc
Working with that is what led to the Acorn Risc Machine, which we all know and love as the ARM architecture
They couldn't afford to make a big chip, so they worked on an extremely small one, and gave it an instruction set that was minimal, but powerful . Just like the 6502.
--
     “I know that most men, including those at ease with problems of the greatest complexity, can seldom accept even the simplest and most obvious truth if it be such as would oblige them to admit the falsity of conclusions which they have delighted in explaining to colleagues, which they have proudly taught to others, and which they have woven, thread by thread, into the fabric of their lives.”
     ― Leo Tolstoy