This post is going to be about Repair of old HP Infiniium 5815A 500Mhz oscilloscope. Scope has normal PC motherboard with Windows 98. Scope has issue booting into windows because DS12887A RTC which scope's motherboard uses has internal battery. And because of RTC battery being empty scope has CMOS checksum bad and can not boot as it has forgotten all boot settings. I will try to fix DS12887A and restore setting to CMOS memory.