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Macintosh LC III Overclocking, 25Mhz to:===>33Mhz


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What is MACSBUG?

 

Also the re-clock we'll call it, makes it a LC-III+

witch is a legitimate model.

 

are you sure you are not doing something odd?

 

MacsBug is a debug console on the Mac, invoked by NMI (command-power btn) http://en.wikipedia.org/wiki/MacsBug

R14 soldered out, and soldered on the empty place R74... I tested the solderings, and as everything was ok finally (except macsbug, and model type recognition) i think the OC was done correctly.

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If its a 000 ohm resistor, would that not mean in fact its not really one at all? Basically a wire link. I know other Macs where instead of moving small resistors one could just create a solder bridge instead. The "resistor" was used simply because it was an easy part to drop in on the board when different combinations of connections applied to different speeds.

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I'm wondering is it possible to make an internal switch, so it would be possible any time to switch OC on/off...

 

Yes, if its a 0 ohm resistor you could add a switch. They makes switches with multiple contacts that would effetely break one connection and make another in one flick.

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double throw, double pull will do it.

 

http://www.mouser.com/ProductDetail/TE-Connectivity-Alcoswitch/A103SYCQ04/?qs=sGAEpiMZZMvudeGI7i40XE%2fMmrHHHc8pUQGytYsMK0I%3d

 

flip 25mhz

flip 33mhz

 

as they are saying, 000 ohms is the same as a solder bridge, just its machine loadable when they are populating boards.

just use some wire wrap to connect the pads to the switch.

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  • 6 years later...

I'm sorry to resurrect such a long dead thread.

I'm thinking of performing this upgrade. However, I'm concerned about the stress on the 25MHz CPU (mine is not a down-clocked LC III+ motherboard but the original with the 25MHz CPU). Would it be too much for the 25MHz CPU in the long run?

Thanks!

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  • 7 months later...
On 4/25/2020 at 12:14 PM, mac512 said:

I'm sorry to resurrect such a long dead thread.

I'm thinking of performing this upgrade. However, I'm concerned about the stress on the 25MHz CPU (mine is not a down-clocked LC III+ motherboard but the original with the 25MHz CPU). Would it be too much for the 25MHz CPU in the long run?

Thanks!


And again, sorry for ancient resurrection as well (this one only 7 months later):  I think if you attach some good heat sinks it would help with a hot CPU. I wouldn’t want to run this mod with full cpu usage 24/7. I plan to do this mod myself later this month and I’ll definitely be attaching some heat sinks. 

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