(41CL) Advantage Pac (41AD) mapped to page 2?

[cdmackay]

[I hope this is an OK place to ask 41CL questions? If there's a more appropriate forum, or list, please tell me off and I'll take it there]

I've just (yesterday) got my 41CL, and am having some initial plays with it. What a great piece of kit

I was looking around at what was mapped on the MMU, and was surprised to find the Advantage Pac (ROM image 41AD) apparently mapped to page 2. That's really page 2, not port 2 (pages 10 & 11).

To verify that, I thought I would reset the MMU and start from scratch.

I did a backspace-ON, verified the MMU was disabled, then did MMUCLR.

I then loaded YFNX (41CL Extreme Functions) to page 6 with PLUGP (having read that this ROM is safe there). Then enabled the MMU.

I then used the YFNX function PLUG to search the mapped modules, with "?IMG ?", which produced:

Code:

41AD 2
YFNX 6

Just to check that, I read the value at RAM physical address 0x80402C, which is the MMU entry for page 2, set 0:

Code:

ALPHA 80402C-0000 ALPHA
YPEEK

which returned 0x800C. The 0x8000 is the MMU Enable bit, and 0x00C is indeed the page for the 41AD module.


Is this expected? I thought pages 0–2 were for the OS itself, and weren't mapped by the MMU? So why does there appear to be a ROM image mapped at page 2?

Most likely I have deeply confused myself, in which case apologies, but would someone please straighten me out? thanks!