Amiga 500plus RTC

madlax · 22 April 2019, 21:57

So I recently picked up a spare Amiga 500plus Rev 8A board. It looks really clean, battery was removed, no signs of corrosion anywhere.

I tested it for a while and when I tried to set the time and date, setclock SAVE says no hw clock found. I checked the board and I noticed that the clock chip wasn't even on it or any clock related components for that matter. At first thought perhaps the previous owner went a bit over board with removing things. Now I realize there is 2 different versions of this board.

http://amiga.resource.cx/photos/a500,8

One of them doesn't have these components.

My question is, since I have a 1MB chick RAM trapdoor card with battery on it, how can I use the RTC on this board. I can see only a memory chick and a battery on it, but no other chips. Is there one with an actual RTC on it
or how can I get the time saved to the RTC.

Thanks!

Daedalus · 23 April 2019, 00:28

Late A500s had 500+ boards in them with Kickstart 1.3 fitted and no RTC so maybe that's the origin of your board.

The A500+ has slightly different signalling for the trapdoor, to avoid conflicts when you install a RAM expansion for the A500 with an RTC on board. So it won't use the RTC of an A500 RAM expansion. You could mod the motherboard to use it by running a wire (or two, it's a while since I looked at it) from the RTC area to pins in the trapdoor and cutting the relevant traces, or you could install the parts yourself. They're very easy to fit if you can use a soldering iron.

cmorley · 23 April 2019, 09:27

JP9 on the 8A board (near Gary) determines if it uses on board RTC or trapdoor RTC.

This is part of the Commodore "sell the same PCB as A500 or A500+" options.

Google "amiga 500+ JP9" or look at the schematic.

madlax · 23 April 2019, 18:42

Looks like it's an easy fix! Thank you both!

madlax · 25 April 2019, 18:29

I closed JP9 and it's working now! Thanks again!

22 April 2019, 21:57	#1
madlax Registered User Join Date: Oct 2017 Location: St. Louis, MO, USA Posts: 60	Amiga 500plus RTC So I recently picked up a spare Amiga 500plus Rev 8A board. It looks really clean, battery was removed, no signs of corrosion anywhere. I tested it for a while and when I tried to set the time and date, setclock SAVE says no hw clock found. I checked the board and I noticed that the clock chip wasn't even on it or any clock related components for that matter. At first thought perhaps the previous owner went a bit over board with removing things. Now I realize there is 2 different versions of this board. http://amiga.resource.cx/photos/a500,8 One of them doesn't have these components. My question is, since I have a 1MB chick RAM trapdoor card with battery on it, how can I use the RTC on this board. I can see only a memory chick and a battery on it, but no other chips. Is there one with an actual RTC on it or how can I get the time saved to the RTC. Thanks!

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23 April 2019, 00:28	#2
Daedalus Registered User Join Date: Jun 2009 Location: Dublin, then Glasgow Posts: 6,343	Late A500s had 500+ boards in them with Kickstart 1.3 fitted and no RTC so maybe that's the origin of your board. The A500+ has slightly different signalling for the trapdoor, to avoid conflicts when you install a RAM expansion for the A500 with an RTC on board. So it won't use the RTC of an A500 RAM expansion. You could mod the motherboard to use it by running a wire (or two, it's a while since I looked at it) from the RTC area to pins in the trapdoor and cutting the relevant traces, or you could install the parts yourself. They're very easy to fit if you can use a soldering iron.

23 April 2019, 09:27	#3
cmorley Registered User Join Date: Jun 2018 Location: Oxford, UK Posts: 66	JP9 on the 8A board (near Gary) determines if it uses on board RTC or trapdoor RTC. This is part of the Commodore "sell the same PCB as A500 or A500+" options. Google "amiga 500+ JP9" or look at the schematic.

23 April 2019, 18:42	#4
madlax Registered User Join Date: Oct 2017 Location: St. Louis, MO, USA Posts: 60	Looks like it's an easy fix! Thank you both!

25 April 2019, 18:29	#5
madlax Registered User Join Date: Oct 2017 Location: St. Louis, MO, USA Posts: 60	I closed JP9 and it's working now! Thanks again!

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