Setting a500+ trapdoor 1MB memory expansionas the default memory (no motherboard RAM)

kipper2k · 10 June 2022, 15:10

Hi All,

I am trying to figure out how i can use the trapdoor memory as default 1MB chipmem memory on an A500+ (Assume there is no onboard memory chips) i have tried various combinations with jumpers and no luck with no luck).

Does anyone have any ideas on how to achieve this.

Thanks.

Niklas · 10 June 2022, 22:55

I don't think there is a simple mod (soldering a jumper) that does what you want.

But if you are not planning to use the on-board memory, and you are fine with doing a slightly larger mod, then you can desolder U32. Under U32 are two jumpers, JP4A and JP4B, and with U32 removed you then bridge pads 2 and 3 on those jumpers to get the effect you are after.

kipper2k · 11 June 2022, 13:29

Awesome, this is great, i am actually doing a massive mod that will help the majority of people. I cant say too much as i have a couple of weeks work left
.

Thanks again!!

Niklas · 11 June 2022, 16:11

That sounds exciting. Looking forward to see what it is!

katarakt · 13 August 2022, 18:15

I have a prototype trapdoor memory expansion board sitting around for a while. The idea behind this was similar: complete replacement of the internal 512k memory + 512k slow but for revision 5 mainboards because it has 16 ram chips and if they are failing it would be nice to use an all-in-one trapdoor expansion.

Rev.5 boards don't have U32...what has to be done on Rev.5 to get it working? Is it possible?

10 June 2022, 15:10	#1
kipper2k Registered User Join Date: Sep 2006 Location: Thunder Bay, Canada Posts: 4,323	Setting a500+ trapdoor 1MB memory expansionas the default memory (no motherboard RAM) Hi All, I am trying to figure out how i can use the trapdoor memory as default 1MB chipmem memory on an A500+ (Assume there is no onboard memory chips) i have tried various combinations with jumpers and no luck with no luck). Does anyone have any ideas on how to achieve this. Thanks.

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10 June 2022, 22:55	#2
Niklas Registered User Join Date: Apr 2018 Location: Stockholm / Sweden Posts: 129	I don't think there is a simple mod (soldering a jumper) that does what you want. But if you are not planning to use the on-board memory, and you are fine with doing a slightly larger mod, then you can desolder U32. Under U32 are two jumpers, JP4A and JP4B, and with U32 removed you then bridge pads 2 and 3 on those jumpers to get the effect you are after.

11 June 2022, 13:29	#3
kipper2k Registered User Join Date: Sep 2006 Location: Thunder Bay, Canada Posts: 4,323	Awesome, this is great, i am actually doing a massive mod that will help the majority of people. I cant say too much as i have a couple of weeks work left . Thanks again!!

11 June 2022, 16:11	#4
Niklas Registered User Join Date: Apr 2018 Location: Stockholm / Sweden Posts: 129	That sounds exciting. Looking forward to see what it is!

13 August 2022, 18:15	#5
katarakt Registered User Join Date: Jul 2017 Location: Germany Posts: 205	I have a prototype trapdoor memory expansion board sitting around for a while. The idea behind this was similar: complete replacement of the internal 512k memory + 512k slow but for revision 5 mainboards because it has 16 ram chips and if they are failing it would be nice to use an all-in-one trapdoor expansion. Rev.5 boards don't have U32...what has to be done on Rev.5 to get it working? Is it possible?

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