Overclocking info

Mervin

I'm trying to figure out if it's possible for me too wire my Propeller chip to a 50Mhz oscillator (the line is shared with other devices, do I need to buffer this somehow?)
and then use PLL2X to run it at 100Mhz while providing 3,6v and mounting a heatsink.

Is this the right way to do this or is the PLL not useable with such a fast oscillator?.

(I understand that by overclocking I am voiding my warranty and might damage the device.)

Mike Green

You can drive XIN from an external oscillator, but you have to use XINPUT clock mode and bypass the PLL that way. XIN can be driven up to 80MHz and probably somewhat more. The highest frequency you could use for an external input to the PLL is about 10MHz. The PLL won't run higher than that and the Prop won't work much beyond about 104MHz for a system clock. There are graphs in the Propeller datasheet showing test data points for system clock speed given different power supply voltages and chip temperatures. With overclocking, you also have to be careful about bypassing the supply voltage pins and the layout of power traces on the board. Generally people have done fine with good board design at 3.3V and commercial temperatures at system clocks around 100-104MHz using the PLL.

pik33

In my experiments the Propeller works stable with 14 MHz/PLL 8x and 7.3 MHz/PLL 16x

It don't work with 15 MHz/8x

PLL always multiplies x16, so 50 MHz/PLL 2x is impossible. Now, as I have said "impossible", maybe someone will do it.

Cog's PLLs works at something about 230 MHz max.