Is it plugged in?



  • This story happened to a buddy of a friend of mine called Ben. Let's call him Ed.

    Back in the days of VAX's they used to share disk drives using Hiearchial Storage Controllers that were very early versions of what is now known as RAID controllers. The collection of VAXes and HSC's were called a cluster.

    An install of one of these clusters went bad when none of the VAX's could see the disk drives and that's when Ed was called in to see what's what. He pulled up his sleeves, dove into the OS code and was analyzing crash dumps to find out that the VAXes were not able to contact the HSC. So, with step one done, he jumped into debugging the code for the HSC and systematically traced the issue down to a bit which was not being set.

    Follwing the wires, he chased the bit back to the control panel for the HSC to find out the bit reflected the state of the "On-line/Off-line" button. He pushed the button and everything worked.



  • So? I do the same thing every time I need to turn on my PC.

    I inspect the motherboard and map all the buses and trace the power inputs and the grounds back to the power supply. I debug the BIOS logic and verify the CMOS data. Finally I follow the wires to the power button on the front panel and, if everything seems correct, I press it.


  • Winner of the 2016 Presidential Election

    @superjer said:

    So? I do the same thing every time I need to turn on my PC.

    I inspect the motherboard and map all the buses and trace the power inputs and the grounds back to the power supply. I debug the BIOS logic and verify the CMOS data. Finally I follow the wires to the power button on the front panel and, if everything seems correct, I press it.

    Perhaps we could build this process into the PC. Every time you turn it on it could examine itself for faults. Let's see... We could call it the Power-On Self Test, or POST for short. Brillant!



  • How do you debug the BIOS logic if the motherboard has no power with which to run the BIOS? 



  • He can remove the actual silicon chip from the BIOS, look at it under a microscope to find the contents of the memory, then run through the entire program in his head and tell if it behaves correctly or not. 



  •  A system I worked ona few years back as still VAX and had 7 disks installed. One day they lost one completely and the most recent backup was 2 days previously. 

     Due the the massively high level of data redundancy in the system we were able to rebuild every single missing file from the rest of the data in the system (that's at least 1/7 of the data in the system that should disappear with normalisation ... )


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