OMG, i thought i will never see this three-digit-code again! ;-))
First, this means you are using a classic R/6000 with a microchannel bus, because the modern PCI-systems have different error codes.
(Blinking) "888" on th R/6000 3-digit-display means "general unrecoverable error" and is similar to the "blue screen of death" in Windows or a kernel panic in Linux. "102-300-0C5" is a more detailed description of the error condition which you should be able to locate in the hardware diagnostics manual accompanying the machine. I did a google-search for "3-digit-code 888" and found this:
IBM
Switch off the thing, power it back on, cross your fingers and pray. Perform the diagnostics routine described in the link and most probably you will have to call a technician - i wonder if there is still hardware support for these systems.
Good Luck.
bakunin