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Using a turbo button to "switch" CPUs

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First post, by peg

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I had a crazy idea of using the turbo button on an AT case to switch between using different CPUs. I have this Cougar Alaris board and it has a built in CPU (386 class Blue Lightning) and also an additional socket 3 for adding an upgraded CPU (486 class or Pentium Overdrive). I believe you simply change a jumper to pick which cpu is used, but I'm not 100% sure since I've never used anything other than the built in CPU.

Could you not wire up a switch (or use the case turbo switch) to switch between using either CPU? Is this even possible and has anyone tried something like this before with this board or another "dual socket" board before?

Perhaps you could even use 2 switches. The existing turbo switch can still be used as is, for downclocking the cpu, and the other switch could be used to pick between the 2 different cpus. In this configuration, you'd have potentially 2 different CPUs each with 2 different speeds, netting a total of 4 possible running configs just from flipping a few switches.

Sounds pretty cool but I have no idea if it would ever work in practice. Even just switching between the 2 cpus by itself would yield vastly different performance in the case of going from the Blue Lightning to say the Pentium Overdrive 83, but having 4 different speeds would be pretty cool.

Reply 2 of 4, by boxpressed

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I can't speak to dual CPU motherboards, but I use the turbo switch to change the FSB speed on my FIC VA-503+ (MVP3). At full speed (100MHz FSB), it is 550 MHz, and with a 66 MHz bus, it runs at 366 MHz. From there, I can use SETMUL to tweak the multiplier and cache settings, meaning that I don't have to open the case to run at a wide range of speeds.

Reply 3 of 4, by peg

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boxpressed wrote on 2020-05-14, 00:51:

I can't speak to dual CPU motherboards, but I use the turbo switch to change the FSB speed on my FIC VA-503+ (MVP3). At full speed (100MHz FSB), it is 550 MHz, and with a 66 MHz bus, it runs at 366 MHz. From there, I can use SETMUL to tweak the multiplier and cache settings, meaning that I don't have to open the case to run at a wide range of speeds.

I have one of those motherboards too, does that all work "on the fly" or do you need to reboot between flipping the switch or using setmul? Also, which cpu are you using with the setup?

Reply 4 of 4, by boxpressed

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peg wrote on 2020-05-14, 01:12:
boxpressed wrote on 2020-05-14, 00:51:

I can't speak to dual CPU motherboards, but I use the turbo switch to change the FSB speed on my FIC VA-503+ (MVP3). At full speed (100MHz FSB), it is 550 MHz, and with a 66 MHz bus, it runs at 366 MHz. From there, I can use SETMUL to tweak the multiplier and cache settings, meaning that I don't have to open the case to run at a wide range of speeds.

I have one of those motherboards too, does that all work "on the fly" or do you need to reboot between flipping the switch or using setmul? Also, which cpu are you using with the setup?

I don't switch on the fly since it doesn't take too much time to shut down and then switch. Here's a thread I started on the build. You need a turbo switch with a three wire connector.
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