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Old 09 November 2018, 12:17   #1
WildW
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A500 1MB Chip Ram

So I was surprised to discover that my new-to-me A500 has 1MB of chip ram (using the trap-door expansion). From what I've read this was something that came in with the A500 Plus and could be added to late revision A500 boards with a modification. I had thought my unit was much older as I have a red power LED and the serial number is fairly low. . . perhaps the board has been replaced at some point, I'm not sure. I forgot to make a note of the PCB revision when I opened it up last.


Anyway. . .what does 1MB chip ram do for me on an otherwise OCS machine? Is there any software that I can run that I otherwise couldn't? So far all I've noticed is that some early software gets upset about it. I tried to run the old Red Sector Demo Maker which thinks I don't have enough memory, but used to run on my old 0.5 chip / 0.5 slow machine. Interestingly it made the same complaint on a 1200 with 2mb chip ram so I'm guessing it may be looking for fast ram specifically, somehow.
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Old 09 November 2018, 13:27   #2
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Almost any A500 can be upgraded to 1MB of Chip RAM by swapping the Agnus and reconfiguring a few jumpers.

The rev5 is moderately easy to do and the rev6 is the easiest.

Usually people make these switchable so that you can revert to the 512/512 configuration for those old pieces of software, that expect it. So yes, some old programs specifically only understand Fast RAM at the $c00000 address, where the trapdoor normally puts it.
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Old 09 November 2018, 13:30   #3
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Is there any benefit to 1MB chip ram? So far it only seems to be causing problems.
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Old 09 November 2018, 13:43   #4
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Benefit: more screens open at the same time, larger music modules possible in protracker.. Basically you can do more with audio/gfx.

If you mainly care about playing games, 512/512 is usually plenty, there are not very many that require 1MB of Chip.
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Old 09 November 2018, 15:08   #5
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Quote:
Originally Posted by Jope View Post
Benefit: more screens open at the same time, larger music modules possible in protracker.. Basically you can do more with audio/gfx.

If you mainly care about playing games, 512/512 is usually plenty, there are not very many that require 1MB of Chip.
The Settlers play on bigger maps and with more sounds, MK2 does not require swapping disks mid-fight for Fatalities... Not sure if there was anything else that required 1MB chip instead of 0,5+0,5...
Ah, yes, Rise of the Robots - pretty, but sh*tty :>
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Old 09 November 2018, 15:25   #6
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The two largest (or only the largest?) maps of Turbo RAKETTI 1 also requires 1MB of Chip. :-)
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Old 09 November 2018, 15:29   #7
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Thanks guys. I think I may investigate if the mod can be easily undone. My 1200 should cover the special cases...
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Old 09 November 2018, 16:31   #8
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It all depends on your motherboard revision.. Perhaps check that first.
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Old 09 November 2018, 20:25   #9
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Revision 6A. I believe it was Professor Plum in the Billiard Room with the craft knife and big blob of solder on JP2.

Edit: Undid these two mods, showing 0.5 chip and 0.5 slow in all the right places And RSI Demo Maker works.



Last edited by WildW; 09 November 2018 at 20:59. Reason: Updated
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