Amiga.org
Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: evil_nerd on May 03, 2004, 01:42:46 PM
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Hello,
I have an Amiga 500 taken from the scrapheap. It works fine! It has 9Mb RAM!!! So I think the previous user was fanathic. I would like to see if there are more hardware expansions. Is there a way to see this?
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You can do an inspection, after having a look at The Big Book of Amiga Hardware (http://hard-ware.de/amiga), or do it the s/w way using the Identify library and its utils (http://wuarchive.wustl.edu/pub/aminet/util/libs/IdentifyUsr.readme), but you have to own a >v2.0 ROM in order to use this (probable, if that guy already has 9MBs of RAM ;-) ).
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Cass wrote:
You can do an inspection, after having a look at The Big Book of Amiga Hardware (http://hard-ware.de/amiga), or do it the s/w way using the Identify library and its utils (http://wuarchive.wustl.edu/pub/aminet/util/libs/IdentifyUsr.readme), but you have to own a >v2.0 ROM in order to use this (probable, if that guy already has 9MBs of RAM ;-) ).
Hmmmm, I don't want to open my Amiga. Maybe there's a rom switcher in it, but when I boot it says I have Kickstart v1.2
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9 megs? that is only possible with a side box. The internal trapdoor can't support that much.
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side-box, or a board that slips under the 68000 :-P
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When I start Workbench, it says 9100000 bytes free (or I must be so stupid to mis see a zero...)
I don't have a side-box or something (but in the port below the amiga is a BIG metal box...)
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Well, you'll never know till you visit the B52-Rock-Lobster :-o
For the uninformed:
Thats the code-name of the A500-mobo :-P
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bloodline wrote:
9 megs? that is only possible with a side box. The internal trapdoor can't support that much.
how much can it support?
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sir_inferno wrote:
bloodline wrote:
9 megs? that is only possible with a side box. The internal trapdoor can't support that much.
how much can it support?
1.5 Meg I think.
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When I start Workbench, it says 9100000 bytes free (or I must be so stupid to mis see a zero...)
I think you're accidentally adding a zero :-) Because IIRC (and my memory is a bit blurry on this one) that's the average amount of RAM you'd have left after WB has loaded on a stock A500 + half meg expansion.
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1.5 Meg I think.
With a GARY chip hack.
(wrt 1.5MB FAST through the trapdoor)
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Lets see now...
The A500 with 68000 CPU supports a maximum of 10Mb RAM.
8Mb of true fast mem
2Mb of chip/"slow fast" mem (min 0.5Mb chip) in a few different combos (0.5/1/2Mb chip : 0.5/1/1.5Mb "slow fast" : max 1Mb total if no Gayle fix)
Now that's the RAM, we aren't counting the 0.5Mb kickstart ROM memory right? ;-)
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The A500 with 68000 CPU supports a maximum of 10Mb RAM.
68000 can address 16MB memory. Depending on the system implementation, all or only part of that can be RAM.
68000 Amiga system memory map:
000000-1fffff chip memory (max 2MB)
200000-bfffff fast memory (max 8MB)
a00000-beffff reserved
bfd000-bfdfff cia-b
bfe001-bfefff cia-a
c00000-dbffff ranger fast memory
dc0000-dcffff real time clock
dff000-dfffff custom register
e00000-e7ffff reserved
e80000-e8ffff auto-config space
e90000-efffff secondary auto-config space
f00000-f7ffff 512KB ROM, total 1MB (cdtv, cd32)
f80000-fbffff 256KB ROM, total 512KB (KS 2.x, 3.x)
fc0000-ffffff 256KB ROM (KS 0.x, 1.x)
In theory it's possible to have 2MB chip, 8MB fast and 1792KB ranger memory, total 12032KB (though it is not trivial to hack both 2MB chip and 1.5+MB ranger). With some extra hacking it might be possible to put some memory into reserved areas like 512K to e00000, and second 512K to f00000.
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Yes.. the 68000 can access 16Mb but the A500 only allows for it to access 10Mb... Or os I though as I didn't know of the Ranger memory so I guess something like 11.6Mb with the ranger memory hack (is there a guide for this anywhere and how will it register, as fast memory?).
I wouldn't go into reserved areas but as you point out there might be a way to gather another 1Mb there if you hack it successfully... though I doubt it.
Realy if one need more than 2Mb chip and 8Mb fast one shouldn't hack the computer but upgrade to a better Amiga or at least look into existing A500 030 turbo board instead. One could even do a SIDECART->CPUSLOT hack and use existing A2000 turbobboards rather than hack the motherboard to peices just for another few Mb of slow memory.