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SubjectRe: MAME memory issues Reply to this message
Posted bygalibert
Posted on03/09/04 05:31 AM

> I'm a little unclear on how to handle mirroring in MAME, maybe someone can help
> out.

You have essentially three possibilites, AM_MASK, AM_MIRROR and AM_SHARE.
- AM_MASK is a mask to apply after testing for AM_RANGE
- AM_MIRROR is an inverted mask to apply to the address (i.e., ignored lines) before testing for AM_RANGE
- AM_SHARE allows to share memory zones

> AM_RANGE(0xc000,0xc7ff) AM_READ(MRA8_RAM) AM_MIRROR(0xf800)

What you want is:
AM_RANGE(0xc000,0xc7ff) AM_READ(MRA8_RAM) AM_MIRROR(0x3800)

> If this means that the mirroring area can exceed the upper bound of the AM_RANGE
> macro ($03FFFF), then wouldn't AM_MIRROR not work for mirrored memory at a lower
> address with something above it? For example in my case, if the RAM was mirrored
> through $C000-$E7FF, but not $E800-$FFFF, AM_MIRROR would still put the mirrored
> RAM in the $E800-$FFFF range, right?

Yes, you'd have to split in in two entries using AM_SHARE, one mirroring over c000-dfff and one at e000.

> Now for handling mirroring of handlers, I'm stuck on this one too:
> AM_RANGE(0x80, 0x80) AM_WRITE(YM2151_register_port_0_w)
> AM_RANGE(0x81, 0x81) AM_WRITE(YM2151_data_port_0_w)
> I'd like to mirror these from $80 to $BF each, so the first one is called for
> I/O ports $80, $82,..$BE, and the latter is for $81, $83,..$BF. Can the
> mirroring macros handle this? Or would it be better to define a handler for the
> full range, manage the mirroring myself, and call the above routines from there?

AM_RANGE(0x80, 0x80) AM_WRITE(YM2151_register_port_0_w) AM_MIRROR(0x3e)
AM_RANGE(0x81, 0x81) AM_WRITE(YM2151_data_port_0_w) AM_MIRROR(0x3e)

You have to read it as "the hardware ignores the address lines 1 to 5 around there", which is very probably what happens in the real thing.


Entire Thread
Subject  Posted byPosted On
*MAME memory issues  cgfm03/09/04 01:44 AM
..Re: MAME memory issues  galibert03/09/04 05:31 AM