The PowerLeap PL-Pro/MMX Plus! adapter fits into socket 5 and 7 motherboards, allowing newer dual voltage CPUs to be used in older systems that only anticipated or were prepared for only single voltage CPUs. The Plus! version allows core CPU voltages of 1.6v to 3.5 volts to be set, in 0.1v increments. I/O voltage, to the best of my knowledge, is expected to be 3.3v, as set on the motherboard. (I did not find any settings listed in the PL manual for changing I/O voltage on the PL unit itself.) CPU clock multipliers are available from 2.0 to 5.5 in 0.5 increments.
The PL-Pro/MMX Plus! also includes CPU temperature sensing and, through PL's CPU Control Panel, can protectively shut down or slow down a system that is overheating. The PL CPU Control Panel is pretty flexible in options when it detects an overheat condition. It can even be set to call a phone number! (The Control Panel also allows registers to be set in the CPU to maximize performance. For example, write allocation gives a noticeable boost on the K6-2.)
The simplest thing the Control Panel software can do in an overheat condition, and one it will automatically do unless overridden, is to slow the CPU speed by half. For example, if overclocking a K6-2/333 to 366 MHz, and an overheat condition is detected, the CPU will slow to 183 MHz. (Still faster than the old PR166+ :)
The PL unit overrides any CPU multiplier settings on the motherboard, but does depend on the motherboard for I/O voltage and bus speed. My Cyrix chip needed 3.5v for I/O (and core), and I needed to change this to 3.3v for the AMD chip. Again, this aspect isn't really covered in the PL manual...
The bus speed will be a big player if you have an older system that only supports a 50 MHz or 60 MHz bus. Maximum upgrade speed will only be obtained with a 66 MHz bus. (Note: many boards will allow higher bus speeds, e.g., 75 MHz, and 83 MHz. I don't have these options and was not able to test them. Your mileage may vary. But I believe many are able to use these higher bus speeds with success and faster results. Tom's has a lot of information on overclocking if you're interested in all the benefits, drawbacks, and concerns.)
Socket 7 (and I suppose socket 4 and 5 as well) systems gain system speed from increased L2 cache speed. The L2 cache on these systems runs at the bus speed. Increasing the bus speed (as long as the system remains stable) will give correspondingly larger overall speed increases than just increasing the CPU core speed. For example, a K6-2/300 (66*4.5) will be overall more slow than a K6-2/300 (75*4.0) just because the L2 cache is accessed much faster in the latter case.
PowerLeap representatives have stated on their discussion board that the PL-Pro/MMX Plus! should be good for much higher bus speeds (at least as high as 100 MHz) for any socket 7 CPUs that can take advantage of the faster bus. Again, YMMV.
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This page last updated 12/21/98