ouch. sounds like you lost a chip somewhere, or maybe a voltage regulator.
Process of elimination:
Time to break out the scope and find out if there is bus activity, and if you still have clock pulses at the proper spots on each chip. See if the ROM is getting called up for access.
Usually a hard freeze means that the system stopped responding to interrupts, and/or other chips stopped receiving control signals. Judging the fact that the screen stayed on during the freeze until you cut the power, That tells me the video ASICs and associated circuitry is ok, and that the system clock is still present and voltages are present within those circuits, or the LCD would have "etchasketched" away when it froze.
Problem goes back to the CPU and/or its memory controller. Something halted the bus/stopped the CPU from responding to interrupts. And since it doesnt boot, that means the CPU/system bus, or something on it is faulty.
Process of elimination:
Time to break out the scope and find out if there is bus activity, and if you still have clock pulses at the proper spots on each chip. See if the ROM is getting called up for access.
Usually a hard freeze means that the system stopped responding to interrupts, and/or other chips stopped receiving control signals. Judging the fact that the screen stayed on during the freeze until you cut the power, That tells me the video ASICs and associated circuitry is ok, and that the system clock is still present and voltages are present within those circuits, or the LCD would have "etchasketched" away when it froze.
Problem goes back to the CPU and/or its memory controller. Something halted the bus/stopped the CPU from responding to interrupts. And since it doesnt boot, that means the CPU/system bus, or something on it is faulty.