(SOLVED) 41CL - DOUBLE HEPAX ACCESS and MMU CONFIG

[Ángel Martin]

(08-23-2019 11:09 PM)rprosperi Wrote:  

(08-23-2019 10:18 PM)Monte Dalrymple Wrote:  Hardware outside the CPU watches for the opcode and acts when it sees it. I use the same technique with the WCMD instruction in the NEWT. Depending on the contents of one nibble in the C register (which is visible on the data bus) the logic sets the Turbo mode, reads or writes physical memory, enables or disables the MMU, etc. I would assume that logic in the Hepax module does something similar.

OK, thanks. I was aware of that in the NEWT (which has power and speed to spare), but did not think the HEPAX module had such sophisticated capabilities back in 1987. The more I learn about it, the more impressive it is.

There are other examples: The Advantage Pac and the IR printer module also act on "special" OpCopes to switch their banks .... so it was not only the HEPAX. Also the ZEPROMS implemented their own bank-switching scheme... so imagine: the NUT CPU is happily NOPing while all that wild bank switching happens ;-)

As to the WRTROM/READROM instructions, absolutely they can be used on HEPAX RAM pages - so the user could (re)store their HEPAX RAM contents on disk.

IN fact, moving to the CL now, the user can have MULTIPLE sets of HEPAX RAM blocks in sRAM and manage them via (UN)PLUG commands to swap the sets on demand.

Even more interesting, with the HEPAX_4H revision two sets of HEPAX RAM pages can be plugged-in simultaneously and the Hepax FileSystem addressing can change the mapping of the respective sets. This requires functions HEPINI and HEPCHN but it really is quite easy.

Impressive indeed...