A500 Rev5 Chip Memory

Lamaman71 · 13 January 2022, 19:31

Hi, Id like to increase my chip RAM from 512 to 1MB. This is a stock OCS with an 8371, I am thinking of popping in a 8372a and believe there are a handful of motherboard mods associated with it. Has anyone here got any experience with this and can advise?

Sinphaltimus · 14 January 2022, 00:58

It's been a very long time since I've done this mod so I can't recall all the caveats or requirements. However, this looks like a pretty good video on how to do it with a rev5 mainboard (mine is also rev5 but NTSC, the one in the vid is PAL, not sure if it's a difference)

[ Show youtube player ]

Jope · 14 January 2022, 09:12

For the ages: Isolate PAL/NTSC pin at the Agnus (piece of kapton), toggle JP2, cut EXROM trace that comes from the trapdoor slot or turn off the switch in your ram expansion.

The A500 schematics are useful here to determine the pins for exrom and PAL/NTSC.

13 January 2022, 19:31	#1
Lamaman71 Registered User Join Date: Sep 2021 Location: Katy, USA Posts: 154	A500 Rev5 Chip Memory Hi, Id like to increase my chip RAM from 512 to 1MB. This is a stock OCS with an 8371, I am thinking of popping in a 8372a and believe there are a handful of motherboard mods associated with it. Has anyone here got any experience with this and can advise?

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14 January 2022, 00:58	#2
Sinphaltimus Registered User Join Date: Aug 2016 Location: Cresco, PA, USA Age: 53 Posts: 1,126	It's been a very long time since I've done this mod so I can't recall all the caveats or requirements. However, this looks like a pretty good video on how to do it with a rev5 mainboard (mine is also rev5 but NTSC, the one in the vid is PAL, not sure if it's a difference) [ Show youtube player ]

14 January 2022, 09:12	#3
Jope - Join Date: Jul 2003 Location: Helsinki / Finland Age: 43 Posts: 9,863	For the ages: Isolate PAL/NTSC pin at the Agnus (piece of kapton), toggle JP2, cut EXROM trace that comes from the trapdoor slot or turn off the switch in your ram expansion. The A500 schematics are useful here to determine the pins for exrom and PAL/NTSC.

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