A501 R5 RAM Expansion - Chip Memory

Lamaman71 · 19 January 2022, 14:49

Hi Folks,

I have an old A501 RAM Expansion and am wondering if there is a modification I can make to it, like the LK1 jumper on the AmigaKit board, that can flip it over to chip ram in an A500 (assuming a new Agnus and JP2) avoiding cutting the ex-line on the motherboard?

Jope · 19 January 2022, 15:52

You need to isolate pin 32 on the expansion connector of the A501.

Lamaman71 · 19 January 2022, 17:34

Thanks Jope - any suggestions on the best way of approaching that?

Jope · 20 January 2022, 09:57

X-acto knife perhaps? The rev5 unfortunately doesn't have a handy solder jumper like the rev6.

Lamaman71 · 20 January 2022, 14:13

Thanks Jope- I guessed I might be cutting tracks and I’ve read the card specifications and diagrams but can’t identify on the board where to cut - it’s not really obvious to me.

Jope · 20 January 2022, 15:33

You can take a multimeter to Gary pin 32, then unplug the RAM expansion and beep out which is pin 32 at the edge connector.

Once you have identified pin 32, then you can see which pin it is on the ram expansion connector and hopefully identify by eye which pin this is on the footprint of the connector. Now you need to isolate this somehow.

However it may be, that the ground connection for this pin is under the connector for the ram expansion, this will make life a bit more difficult. I guess there's a reason why people modified the Amiga instead.

If you want a totally cut free solution, you can stack sockets under Gary which isolates pin 32 and adds a 4.7k pullup to that pin.

Lamaman71 · 28 January 2022, 00:22

Sorry about the late follow-up. I chickened out and got the Amigakit 512MB ram expansion replete with the appropriate jumper. I fixed up JP2 and hey-presto - I now have 1MB Chip Ram - and the Amiga seems to be much much happier. Thanks for all the advice but fiddling around with Gary (no smutty remarks!) seemed a bit OTT for the sake of a cheap Amiga Kit RAM expansion.

Jope · 28 January 2022, 10:37

Good that you got it sorted.

Your solution is the one I would have recommended too, but not everyone wants to spend extra money. :-)

19 January 2022, 14:49	#1
Lamaman71 Registered User Join Date: Sep 2021 Location: Katy, USA Posts: 154	A501 R5 RAM Expansion - Chip Memory Hi Folks, I have an old A501 RAM Expansion and am wondering if there is a modification I can make to it, like the LK1 jumper on the AmigaKit board, that can flip it over to chip ram in an A500 (assuming a new Agnus and JP2) avoiding cutting the ex-line on the motherboard?

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19 January 2022, 15:52	#2
Jope - Join Date: Jul 2003 Location: Helsinki / Finland Age: 43 Posts: 9,861	You need to isolate pin 32 on the expansion connector of the A501.

19 January 2022, 17:34	#3
Lamaman71 Registered User Join Date: Sep 2021 Location: Katy, USA Posts: 154	Thanks Jope - any suggestions on the best way of approaching that?

20 January 2022, 09:57	#4
Jope - Join Date: Jul 2003 Location: Helsinki / Finland Age: 43 Posts: 9,861	X-acto knife perhaps? The rev5 unfortunately doesn't have a handy solder jumper like the rev6.

20 January 2022, 14:13	#5
Lamaman71 Registered User Join Date: Sep 2021 Location: Katy, USA Posts: 154	Thanks Jope- I guessed I might be cutting tracks and I’ve read the card specifications and diagrams but can’t identify on the board where to cut - it’s not really obvious to me.

20 January 2022, 15:33	#6
Jope - Join Date: Jul 2003 Location: Helsinki / Finland Age: 43 Posts: 9,861	You can take a multimeter to Gary pin 32, then unplug the RAM expansion and beep out which is pin 32 at the edge connector. Once you have identified pin 32, then you can see which pin it is on the ram expansion connector and hopefully identify by eye which pin this is on the footprint of the connector. Now you need to isolate this somehow. However it may be, that the ground connection for this pin is under the connector for the ram expansion, this will make life a bit more difficult. I guess there's a reason why people modified the Amiga instead. If you want a totally cut free solution, you can stack sockets under Gary which isolates pin 32 and adds a 4.7k pullup to that pin.

28 January 2022, 00:22	#7
Lamaman71 Registered User Join Date: Sep 2021 Location: Katy, USA Posts: 154	Sorry about the late follow-up. I chickened out and got the Amigakit 512MB ram expansion replete with the appropriate jumper. I fixed up JP2 and hey-presto - I now have 1MB Chip Ram - and the Amiga seems to be much much happier. Thanks for all the advice but fiddling around with Gary (no smutty remarks!) seemed a bit OTT for the sake of a cheap Amiga Kit RAM expansion.

28 January 2022, 10:37	#8
Jope - Join Date: Jul 2003 Location: Helsinki / Finland Age: 43 Posts: 9,861	Good that you got it sorted. Your solution is the one I would have recommended too, but not everyone wants to spend extra money. :-)

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