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Old 19 March 2008, 08:24   #1
Impakt
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Trapdoor expansion options for A500

Hi all,
Over the last couple years I've been collecting various bits for the A500s i plan to setup again. Currently I have a few A500s, Action Replay carts, (Mk I,II, and III), the ICD adIDE adapter (lets you autoboot IDE hard drive from the A500), and a Chip-Ex B/ MegaChip (I think that's what it's called - 8375 agnus with 1.5mb or 2mb ram).

I was after a decently sized trapdoor expansion (assuming it works with the Chip-Ex), but can't them anywhere (new or 2nd hand). How big could they get without the need for loading up custom drivers? At the moment I have a couple 512kb expansions but remember when i bought my a500 that 2mb expansions were available.

Thanks,
Impakt

Last edited by Impakt; 19 March 2008 at 12:02.
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Old 19 March 2008, 11:29   #2
alexh
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Trapdoor expansions can be 512Kbytes on regular A500 and 1Mbyte on A500+

Anything over that and they have to connect to something else as well as the Trapdoor connector (e.g. the 68000 or Gary) because there are not enough address lines etc.
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Old 19 March 2008, 12:03   #3
Impakt
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Thanks for the response. After doing a bit of searching around here this evening, I noticed that the Chip-Ex is basically exactly the same as the Megachip.

Hopefully this mod will be compatible with a big trapdoor expansion.

My aim is to setup an Amiga 500 with internal hard drive, action replay, and heaps of ram..
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Old 19 March 2008, 12:25   #4
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Try and get an accelerator instead.

Viper A520 / A530
VXL030

etc.
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Old 19 March 2008, 19:17   #5
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Make sure you get the manual when you install your big ram board.. You will need to carefully configure it to avoid duplicating RAM in any memory address.
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Old 20 March 2008, 02:01   #6
Impakt
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So what's the most amount of ram i could hope to get in the a500 by only using the trapdoor slot and the Megachip?

Any shops still selling > 0.5mb expansions or is eBay my only option? Are there any schematics on making your own expansion?

Thanks!
Impakt
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Old 20 March 2008, 06:08   #7
rkauer
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Quote:
Originally Posted by Impakt View Post
So what's the most amount of ram i could hope to get in the a500 by only using the trapdoor slot and the Megachip?

Any shops still selling > 0.5mb expansions or is eBay my only option? Are there any schematics on making your own expansion?

Thanks!
Impakt
The maximum on the trapdoor expansion is one A501 or similar (512kb)! With the Megachip the total amount are 2Mb chip RAM, no more.

Other memory will be added as FAST RAM, if you grab an accelerator or an A590 (plus 8Mb RAM).
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Old 20 March 2008, 07:05   #8
coze
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Megachip is for increasing Chip ram. It can be maximum 2 mb.

Trapdoor slot AFAIK adresses a memory range called 'ranger memory'. it is normally 512k, but with a gary adapter you can have 1.8 mb fast ram there.

So that maximum you can get with chip ram adapter and trapdoor expansion slot is 2mb chip + 1.8 mb fast (with gary adapter).

Note that on A500+ the trapdoor slot is used to increase chip mem, so you probably can't have fast mem cards there (somebody correct me).

Also please note that AR is made with a basic unexpanded A500 configuration in mind. Some expansions may create conflicts with it. Also it doesn't even work with any kickstart over 37.299 (conflicts with gayle adresses ?)

Finally A590 gives you 2mb fast ram, not 8 (but yeah lots of other harddisk controllers do give 8mb fast ram).
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