A500 1MB chip RAM switch

LordCrass · 18 August 2023, 23:13

I was thinking of putting a switch into my A500 to toggle between 512kB+512kB and 1MB chip RAM configurations, but I'm leery about hauling address lines across the case and through some dodgy switch. I've done this with C64 equipment at 1Mhz with no issues, but I don't know if 7Mhz is going to be a problem.

Anyone else done this and can comment on whether they've encountered stability issues as a result?

Jope · 19 August 2023, 08:48

We did this many times in the 90s. It didn't seem to make the machine any more unstable than what it is anyway. :-)

LordCrass · 19 August 2023, 16:25

Good to know, thanks. I was hoping I wouldn't have to come up with some transistor based or solid state relay type solution.

LordCrass · 03 September 2023, 05:46

Happy to say that I have not had any issues as a result of this modification.

Are there any games that require the trapdoor memory to be disabled altogether? I'm wondering if it's worth setting up a 1MB chip/512kb slow/OFF setup, as it would require an DPDT ON/ON/ON switch that I can't seem to find for less than about $18 for a pack of three..

Any game I've seen that didn't like 512kb slow mem was happy if I switched it to 1MB chip.

giantclam · 03 September 2023, 07:27

I think there's a few OCS games like that ... bit of a list here so related https://eab.abime.net/showthread.php?t=65574

18 August 2023, 23:13	#1
LordCrass Registered User Join Date: Feb 2021 Location: Undisclosed Posts: 52	A500 1MB chip RAM switch I was thinking of putting a switch into my A500 to toggle between 512kB+512kB and 1MB chip RAM configurations, but I'm leery about hauling address lines across the case and through some dodgy switch. I've done this with C64 equipment at 1Mhz with no issues, but I don't know if 7Mhz is going to be a problem. Anyone else done this and can comment on whether they've encountered stability issues as a result?

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19 August 2023, 08:48	#2
Jope - Join Date: Jul 2003 Location: Helsinki / Finland Age: 43 Posts: 9,920	We did this many times in the 90s. It didn't seem to make the machine any more unstable than what it is anyway. :-)

19 August 2023, 16:25	#3
LordCrass Registered User Join Date: Feb 2021 Location: Undisclosed Posts: 52	Good to know, thanks. I was hoping I wouldn't have to come up with some transistor based or solid state relay type solution.

03 September 2023, 05:46	#4
LordCrass Registered User Join Date: Feb 2021 Location: Undisclosed Posts: 52	Happy to say that I have not had any issues as a result of this modification. Are there any games that require the trapdoor memory to be disabled altogether? I'm wondering if it's worth setting up a 1MB chip/512kb slow/OFF setup, as it would require an DPDT ON/ON/ON switch that I can't seem to find for less than about $18 for a pack of three.. Any game I've seen that didn't like 512kb slow mem was happy if I switched it to 1MB chip.

03 September 2023, 07:27	#5
giantclam Registered User Join Date: Jan 2015 Location: australia Posts: 534	I think there's a few OCS games like that ... bit of a list here so related https://eab.abime.net/showthread.php?t=65574

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