Exactly, as gerald has said, X-MEM is a ROM/RAM board, there is not ACID there, neither a cpu accelerator.
But of course, depending in the use of the CPC+ cartridge special paging modes used by the game, those cart games could be patched to run from a romboard in a CPC+ (with a cartridge with an ACID for booting the machine).
Remember, the CPC+ lets that the first 8 rom pages in the cart can be selected as lower rom and they can be visible in address $0000, $4000 (new) or $8000 (new). And of course in $C000 when they are used as upper roms. You can see here:
http://www.grimware.org/doku.php/documentations/devices/gatearray#rmr2 Basically you select in the 3 lower bits, which of the 8 first rom pages in the cart is going to be the "new lower rom" and then you select where this lower rom is going to appear in memory ($0000, $4000 and $8000).
I took a look to a few cpc+ cartridge games.
Starting in Robocop 2, we can start for searching all the LD BC,$7FAx and LD BC,$7FBx followed by OUT (C),C (there is more ways, but this is the usual way).
The only LD BC,$7FAx that i found were LD BC,$7FA0 in other words, they are using it only for disabling the ASIC ram. Well that is good news, that means Robocop is not putting the lower rom in $4000, over the asic ram, that is not so stupid because you could make that for try to copy things over asic ram. Ok, time to look the other.
For LD BC,$7FBx, i get exactly:
LD BC,$7FB8
LD BC,$7FB9
LD BC,$7FBC
LD BC,$7FBD
LD BC,$7FBE
LD BC,$7FBF
The possibilities were from $7FB8-$7FBF, everything except $7FBA and $7FBB. This means they are using cart rom pages 0,1,4,5,6 and 7 as lower rom mapped in $0000 while they enabling the ASIC ram.
Why this? Well, you can imagine, for copying things to the ASIC ram (sprites images, coords, colours, etc...). And mainly this code is run from RAM, that means it could be possible to change those OUTs to $7Fxx for OUTs to $DF00, and the code for copy from $C000 instead. And that could work except in case of they mapped a upper rom simultaneously in $C000 for copying things, but i doubt it
Looking other CPC+ cartridge, Batman (yes that game is similar to the tape version
)
Number of access to $7FAx, only two and they are to $7FA0 for disabling the ASIC after put the palettes for the loading screen and the game xDDD
Use of $7FBx, 3 times, always to $7FB8 (rom 0 as lower rom and mapped in $0000) and used only for enabling the ASIC RAM for putting the palettes (and one of them is for putting a black palette XDDD).
Yes, this game could be ported to a rom board with not too much problems.
Looking other games, Pang looks similar to Robocop, but sometimes even shows the lower rom (remember rom page 128 in CPC+ cart) as an upper rom in $C000. For that in the worst case we can duplicate this rom page and patch the code for show this as upper rom X
Although it looks that use one of the first 8 roms as lower rom in $0000 and simultaneously the "lower rom" (cart page 0) in $C000, that it could be a little awkard for us, because uses the contrary to a rom board, upper roms go in $0000 and lower goes in $C000. It would need more work, but it could be possible
Plotting use the normal $DFxx for paging as upper roms, maybe is easy to fix too.
Navy Seals is the more complex, because put the Lower rom over $4000 and then the upper goes in $c000. Maybe the most difficult to patch in a first look.
The list of CPC+ games is short, in cpc-power appears 33 files when i search for gx4000, but if i ignore hacks, diagnostic cartridges, the jukebox, etc... We have:
Barbarian II
Batman
Burning Rubber
Copter 271
Crazy Cars II
Dick Tracy
Epyx World of Sports
Fire and Forget II
Klax
Mystical
Navy Seals
No Exit
Operation Thunderbold
Pang
Panza Kick Boxing
Pinball Magic
Plotting
Pro Tennis Tour
Robocop II
Skeetshot
Switchblade
Tennis Cup II
The Enforcer
Tintin on the Moon
Wild Streets
Only 25 games, and not too much games to patch and not everyone of those should be patched because they are exactly the same game than the normal CPC version and for those the old tape/floppy versions can be used perfectly.
