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Old 26 January 2019, 21:02   #1
Ridrok
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Old big memory expansion questions

Hello,


I have 2 Amiga 500 (and accelerated 1200, CD32... but let's fucus on the 500).
One A500 has a rev 5 board and has a strange 1.5Mb expansion split in 2 parts. I am not even sure it's 1.5Mb since it's plugged on an OCS Amiga 500.



My plan is to move this expansion to the second A500 which has a rev 6a board and a Fatter Agnus supporting 1 MB chip ram.



The expansion I want to move is divided in 2 parts and I wonder if it's possible to make it slow fast + chipmem upgrade. Meaning resulting in 1 MB chipmem and 1 MB slow fast?

I plan to dig my ceiling and find back my old GVP HD8+ to connect to this Rev 6a Amiga 500 and I really would like to have 1 MB chipmem in it.

Many thanks in advance.
Ridrok
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Old 27 January 2019, 08:54   #2
Jope
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The machine being OCS makes no difference to the amount of RAM you can put in the C00000 area.

If it is possible to configure one bank as Chip RAM is dependent on the GARY board, does it have any jumpers on it for you to adjust?
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Old 27 January 2019, 12:32   #3
Ridrok
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No unfortunately there is no jumper.

I found what card it is, it's 1MB board:
https://www.bigbookofamigahardware.c...t.aspx?id=1094

And the second one seams to be a little better version than this one with battery backup clock, it's probably a 512KB board:
https://www.bigbookofamigahardware.c...t.aspx?id=1091

I am not too bad in soldering and I have the tools to solder and disolder, maybe it's possible to mod this Gary board?
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Old 27 January 2019, 14:07   #4
voxel
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the second board is a classic commodore A501 without it's metal shell, nothiing more. 512 KB expansion $C000000 Slow-Fast ram.
can be used as 512 KB Chip ram (to get 1MB of chip) on moded A500 or A500+.
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Old 27 January 2019, 15:32   #5
Ridrok
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Hello Voxel,

Yes I know the second one is a A501, I did remove the shield to remove the battery and not yet added a CR2032 with the needed diodes to prevent the Amiga from charging it.

I would prefer to mod the Zydec Gary adapter to have 1MB Chip ram and 1MB Slow-Fast ram rather than changing the jumper on the Amiga ECS board. This would give me 1Mo Chip ram but no Slow-Fast ram which is needed by some games.
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Old 27 January 2019, 21:50   #6
hooverphonique
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If you're going to add the hc8+ anyway, put fastram in that, instead of bothering with slow-fast. 1MB chip and 4 or 8 MB fast will be a kickass A500.

Unless it's a "because I can!" sort of deal, in which case I encourage you to hack away :-)
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Old 28 January 2019, 00:35   #7
Ridrok
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Yes, the hd8+ I have has (if I remember well) 8 MB of fast ram in it and a ~50 Mo HD, I still have to dig to find it.

You are true with "because I can!"
I know I could buy this kind of board:
https://www.ebay.fr/itm/2MB-RAM-upgr...y/273319974886
But I want to stay with 1990 parts if possible and this is why I ask how and if it's possible to make this Zydec Megaboard a MiniMax Plus.
If not I will put the A501 in and change J2 and J7A to have 1 Mo Chip ram, but I would love to have some Slow-Fast at #C000000 for the sake of having it.
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Old 28 January 2019, 22:13   #8
Ridrok
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Hi

I recovered my HD8+
Here it is, it's in near new condition:



I use MKick to load the 37.175 Kickstart from the HD at boot to keep the 1.3 rom for old games.
Now I need 1MB Chip ram.
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Old 28 January 2019, 22:51   #9
demolition
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For those 1.5/2M boards that allow parts to be remapped into chip usually have a 3rd PCB in the CPU socket so I think your expansion only allows for 1.5MB $C0 mem (or ½M chip without any slow mem).
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Old 30 January 2019, 17:50   #10
Ridrok
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Ok, then I will try to find a Gigatron Mini Max Plus but I doubt I can find one.

Last question then, what about populating the missing 512KB onboard?
I red it disable the expansion slot. Is there any way you would know to add the 512KB onboard and still have the expansion port working for Slow-Fast mem?

Many thanks
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