Re: New pmap module for m68k

[Romain Dolbeau <romain%dolbeau.org@localhost>]

Le dim. 9 nov. 2025 à 19:18, Jason Thorpe <thorpej%me.com@localhost> a écrit :
>(...) natively works with the 3-level table configuration of the 68040 while also natively working with he mandatory 2-level configuration imposed by the HP MMU found in the HP 9000/320 and 9000/350.

Out of curiosity: what does that mean for other MMUs ? Like the '030,
or the Sun-style MMUs ? They stick with the current model ?

> One of the reasons I wanted to do this is so that larger memory configs can be supported on 68040

Good news! and ...

> successfully booted NetBSD/virt68k multi-user with a 2G RAM configuration

... excellent result. Congratulations! No reason for a virtual machine
to not have as much memory as a 32-bits CPU can support.

Is the 2 GiB a hard limit of this new design (rather than the QEmu
machine model), or would it be possible to go beyond that by using
"tricks" on the physical side, such as using the UPA bit as additional
address bits ? (The pins are driven by the bits in the MMU IIRC, so I
think in theory they could be used to generate a 2^34 bytes physical
address space, should that be potentially useful.)

Cordially,

-- 
Romain Dolbeau