A2000 A2630 hardware on/off switch

[blakespot]

Is there any chance that a hardware mod could be done to physically switch the A2620 (68020 accelerator preceding the A2630) off?

I am noticing more and more demos that suffer from the '020 being active and the slight lag it introduced to the system vs. a 68000 for tightly coded demos targeting the base hardware.


bp

[blakespot]

I want to try this with my A2620 - the schematics seems similar:

https://www.amigawiki.org/dnl/schematics/A2620.pdf


So, I would break the 68KMODE signal line coming out of 303 and connect it to a pull-up resistor to ground and also to 305 with a switch and that would do it? Can you give more info as to what type of resistor I would need here? Can you expand a bit on your suggestion looking at the schematics, as I am fine with soldering but not so much digital logic as far as my experience vs a class 30 years ago in my CS degree pursuit. Thanks!


bp

[blakespot]

Thank you. Is there any chance you could sketch out this switch logic for me? Would a three-pole switch be used? One to ground, one to pullup resistor which goes to VCC and the 68KMODE line? I can't visualize it for certain - but solder well enough.

Or perhaps language that Chat-GPT could used to render such a circuit -- in my asks, I don't feel that I'm picturing this right based on the output.

Thanks either way. I'm trying to see if I can keep and use this accelerator (I need a switch, the softswitch boot select doesn't preserve beyond a reboot) or if I need to pull it and go pure 68000 for my particular needs. I need pure 68000 more often than accelerated. Thanks.


bp

[blakespot]

What you need is already sketched out in the schematic. Look at the RAMSIZ, NORAM and B2000 jumpers. The only difference is that you would substitute an SPST toggle switch in place of the jumper.

I see the piece you're talking about, but I guess it's just beyond me a bit -- I can't quite see what I need, from that. I can't clearly envision how the resistor and ground and +5 VCC would tie together with a switch. I will probably remove the A2620 and just run 68000 only. I don't do that much on Workbench, but my main focus is perfect execution of demos.

I may in the future if the slow Workbench is too painful look at a modern accelerator with an on/off switch as a feature.

Thanks.

[blakespot]

If you can't clearly envision this simple circuit, then you are not (yet) at a technical knowledge level needed to perform this modification. I would suggest that you solicit help from someone with the technical skills to do the mod for you.      

I could do the solder work, but I'm not 100% on the layout, and whether to cut a trace and solder there, or cut a pin and solder there, etc.

I keep looking for a switch-laden 3rd party A2000 accelerator coming thru eBay, but nothing. And I'm sure it would be quite pricey, looking at some of the things I do see coming through. (There's an 030 Derringer there now, but that seems not the ideal way to go on the A2000, direct to socket, etc.)

Are you aware of anyone in this forum community that would be willing and able to do this mod for me, for some level of compensation? Thanks.

I feel like I am kind of in a limbo with my A2000 having noted the issues that make me seek a switchable accelerator.

bp