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(SOLVED) 41CL - DOUBLE HEPAX ACCESS and MMU CONFIG
08-23-2019, 05:43 AM (This post was last modified: 08-23-2019 11:13 AM by Ángel Martin.)
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RE: (SOLVED) 41CL - DOUBLE HEPAX ACCESS and MMU CONFIG
(08-23-2019 02:23 AM)Sylvain Cote Wrote:  What was really great at the time the HePaX was made available, 1988 or late 1987 I think,
was the capability to move RAM page(s) outside of the file system and made them as Q-ROM instead.
That instantly made obsolete external Q-ROM boxes for assembly language development.
Just imagine what would had happened if the HePaX modules has been made available five years earlier.

Absolutely, it was the ultimate MLDL-into-a-chip concept, an absolute tour de force ':-)
Even by today standards (NoVoRAM is even better as it preserves the RAM content unplugged and it's re-configurable of course) so back in 1988 it was truly revolutionary.Add to that the software with special OpCode to relocate itself into the lowest available page - an amazing feat!! The holy grail according to some ;=

PS. you're not likely to be familiar with the HEPAX initialization during the CAL_ON event, but it's a piece of SW art. The HEPAX first gets plugged into the lower page of the port where it is physically plugged, and it immediately runs some initialization code. That code establishes the bus parameters, and uses that information to write a code stub in the HEPAX RAM page. That small routine is then executed (!), which thanks to the custom OpCode re-allocates the HEPAX ROM into the smallest page available - and provides XROM id#'s for all the HEPAX RAM pages as well.

In two words: A-Mazing ;-)
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RE: (SOLVED) 41CL - DOUBLE HEPAX ACCESS and MMU CONFIG - Ángel Martin - 08-23-2019 05:43 AM



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