Upgrade for the " EN and LX" older motherboards that use Celeron Black fiber CPUs only (300- 533 MHz), the motherboards will recognize this green fiber CPU because this was a very early Coppermine-128 model without the "Coppermine lockout bios" that made them not backward compatible. However you must use a strong CPU Fan and be able to reduce the CPU voltage to 1.75 or less volts.
Also works well with "Sloket" Slot 1 adapters in LX and EN slot 1 motherboards.