A500 Trap Door Cards?

[Secretary-Bird]

I was going through my shed and assorted old A500 consoles caught my attention, so I decided it was time to finally get one of them set back up (especially since I found my A590 unit, which I thought had been sold off a few years back during the "dark times".)

So anyway, I've been keeping busy testing consoles to determine which one will be "the one". And something that caught my notice was the different types of cards found under the "trap door".

Specifically, there are 3 different styles:

http://i4.photobucket.com/albums/y129/Scarletdown/Misc-Stuff/A500-Cards-1.jpg

The one in the metal case is the most common.

The green one is from Supra (A500 RAM/Clock) and the yellow one has no identifying markings at all.

http://i4.photobucket.com/albums/y129/Scarletdown/Misc-Stuff/A500-Cards-2.jpg

Are these 3 all functionally identical, or is there one that is superior in some way to the others?

[Harrison]

They should all function pretty much the same. Giving 512KB or ram and a realtime clock. The one with the button battery is probably more useful these days as the battery can be swapped out easily and won't leak, whereas the yellow card's battery is very prone to leaking and can damage the internals of the A500 if it does.

The one with the metal shield is probably a Commodore made one. They always seemed to encase their trapdoor expansions in metal shielding, whereas most others didn't and just supplied the naked board.

The only different can sometimes be how the A500 sees the ram. Some trapdoor expansions will show the extra 512KB ram as fast ram, others will see it as slow ram (but still report it in the Workbench as fast ram), and some will be seen as Chip ram and give the A500 1MB chip ram (if it has the newer fatter Agnus chip that supports more chip ram). Only way to tell is to try each card in an A500.

There were a lot of different trapdoor memory expansions produced for the A500 in lots of different sizes and designs. They are however quite rare these days to fine so they are sort after by Amiga users.