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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: hoptoit on October 13, 2010, 07:02:12 AM
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Looking to track down a good RAM upgrade for my A500. I was planning on finding a CPU piggyback expansion until I found this post:
Generally the best way to combine expansions is to not use ones that mix address space on different buses. i.e. trapdoor expansions should stick to the trapdoor Slow RAM portion of the memory map, and the CPU-only portion should go on either a CPU piggyback or on the sidecar.
CPU piggyback expansions are particularly problematic because they, by their nature, can muck with the entire memory map that the CPU sees. I strongly recommend that the only expansion you place there be a CPU card, and if it has any RAM on it it should be true 32-bit RAM that the rest of the system can't see anyway. If you put anything 24-bit on the CPU socket, don't put anything on the side expansion slot. Well-designed stuff should play nicely via autoconfig, but there's no way to guarantee this will happen. There were a few 32-bit CPU cards that went on the side slot (GVP made one, I recall). If you use any of those try to avoid putting anything on the CPU socket.
My goal is to setup an A500 for running games off disk for my brother's kids. I don't really want to add anything else external onto the machine through the CPU slot, but rather keep it as simple as possible for its 5-7 year old endusers. My current config is stock Rev 6a with a single 512k expansion in the trapdoor. No Chip RAM mods or anything done to Angus/Gary. I'm not looking to run WHDload for the present, and I don't have any IDE/HD/CF interfaces of any kind. But I still think a little more RAM would be helpful.
One fellow on Amibay has built a 2MB CPU piggyback plus IDE interface board. However, it has no auto-config support on the board itself and always needs a bootdisk. The other possibility I found was this 8MB CPU piggyback card made by Elbox. But 8MB Fast RAM is really beyond what I need for running disk based games:
http://www.buy.elbox.com/cgibin/shop?info=660E500
I haven't really even looked at doing anything with Chip RAM yet. Any advice what route to take?
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If all you're looking to do is play games off floppy - no need to do anything at all with your current config besides get a second floppy drive and obtain more games!
90+% of Amiga games will work with 512k Chip RAM and 512k FAST. Or 1MB Chip - doesn't matter. You're good to go either way.
Do not fix what is not broken!
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Not too much trouble to do it so I ordered some 256 DRAM DIPS from Nathan's shop to do the real 1 MB Chip RAM upgrade. I will pull out the old 512k card afterwards.
I will keep an eye out for a good CPU piggyback expansion in the future in case I wanna get in to WHDload land. It seems better than trapdoor options.
This project looks to be interesting if someday completed:
http://www.students.tut.fi/~leinone3/ram68k/
I wonder if the 16-bit RAM it plans to use a good match for the A500? Does it make a big difference what RAM type goes through the CPU slot?
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90+% of Amiga games will work with 512k Chip RAM and 512k FAST. Or 1MB Chip - doesn't matter. You're good to go either way.
I doubt there are any non AGA games that will require more than that, although some games may take advantage.
The 2mb chip ram upgrade was good because it left the trapdoor available, at one point I had 1.5mb there as well (plus 2mb on the expansion slot).
I had a blizzard 14mhz accelerator which plugged into the CPU slot with it's own ram, which stopped the action replay from working :-(