CPU hardware Toggle Swich for A2620?

kjmann14 · 14 May 2011, 21:12

Does any one know if it is possible to install some sort of toggle switch to change CPU's in the A2000 using the A2620 Accel Card instead of having to use the Mouse button software switch?

Loedown · 15 May 2011, 03:44

I don't know that particular board, but it will be relying on a signal from something, you only need to set up some simple hardware to look at the state of a switch to see if it gets that signal or not.

SpeedGeek · 15 May 2011, 18:51

Why you would want to do this is a mystery to me. If you look at the A2630 schematics (as a substitute for A2620) the 74LS174 @ U303 generates a 68KMODE signal. If you disconnect pin 15 of the 74LS174 (by cutting the pin close to the PCB) and then connect a 1K pull up resistor to the 68KMODE signal trace and VCC your A2620 will boot in 68000 mode. By adding a toggle switch to jumper the 68KMODE trace to ground you can select 68020 mode. I hope it's worth the effort.

Loedown · 16 May 2011, 06:17

Quote:

Originally Posted by SpeedGeek

Why you would want to do this is a mystery to me. If you look at the A2630 schematics (as a substitute for A2620) the 74LS174 @ U303 generates a 68KMODE signal. If you disconnect pin 15 of the 74LS174 (by cutting the pin close to the PCB) and then connect a 1K pull up resistor to the 68KMODE signal trace and VCC your A2620 will boot in 68000 mode. By adding a toggle switch to jumper the 68KMODE trace to ground you can select 68020 mode. I hope it's worth the effort.

Cheers Speedgeek, I knew there would be a simple way, just wasn't sure exactly how without knowing the board.

14 May 2011, 21:12	#1
kjmann14 Registered User Join Date: Feb 2009 Location: Texas, USA Posts: 121	CPU hardware Toggle Swich for A2620? Does any one know if it is possible to install some sort of toggle switch to change CPU's in the A2000 using the A2620 Accel Card instead of having to use the Mouse button software switch?

15 May 2011, 18:51	#3
SpeedGeek Moderator Join Date: Dec 2010 Location: Wisconsin USA Age: 60 Posts: 842	Why you would want to do this is a mystery to me. If you look at the A2630 schematics (as a substitute for A2620) the 74LS174 @ U303 generates a 68KMODE signal. If you disconnect pin 15 of the 74LS174 (by cutting the pin close to the PCB) and then connect a 1K pull up resistor to the 68KMODE signal trace and VCC your A2620 will boot in 68000 mode. By adding a toggle switch to jumper the 68KMODE trace to ground you can select 68020 mode. I hope it's worth the effort. Last edited by SpeedGeek; 15 May 2011 at 19:33.

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15 May 2011, 03:44	#2
Loedown Precious & fragile things Join Date: Feb 2009 Location: Victoria, Australia Posts: 1,946	I don't know that particular board, but it will be relying on a signal from something, you only need to set up some simple hardware to look at the state of a switch to see if it gets that signal or not.

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