thought i'd give y'all an update...
the MB128 fits into a Duo control port (not a turbo) and you plug one duo pad into the memory base (it would be neat if the thing also doubled as a Duo Tap).
It runs on 4 AA batteries and has a totally sweet "low battery" light that comes on when...you guessed it! The batteries are low!
ok, seriously though, the thing seems pretty cool if you have some games that use it. I only have Brandish, so i'll talk about that.
i can't read the manual for Brandish and a brand new MB doesn't come with a manual, but this is what i've figured out.
Normally you can only save two slots for brandish on a duo without the MB.
When you have the MB hooked up you can save 10 Brandish game files. one of the menu options on Brandish seems to format the MB, which you have to do before you can save games.
with the base, you no longer have access to the main Duo memory bank while playing Brandish. The MB doesn't affect normal games like Y's.
I don't know how much it takes to fill the MB128 up because i don't have any other games that use it.
You can take the batteries out and replace them while the Duo is turned on and you will not lose of your save data on the MB.
in the one in a million chance that you know another human being that owns a Duo, you could take the thing over to your buddy's house and access all your saved games on his dozens of rare PC Engine imports that are Memory Base128 compatible!
OK that's all for the MB128.
on a side note, i recently picked Might Magic 3 and i can't believe how much memory this thing uses on my Duo! it's bigger than 3 saved Dragon Slayer files. when you have a MM3 game saved you pretty much can't use your file space for anything else. fortunately, i have a Tennokoe bank, but it would suck back in the 90s if you picked MM3 up in a toy store and didn't have access to any import technology. i beat MM3 on a Mac back in the day and it took something like three months to get through. that would be a long time not to be able to play any other TG rpgs.