FAT Disk is kaput

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Thomas Okken
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Joined: Tue May 02, 2017 5:48 pm
Location: The Netherlands
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Re: FAT Disk is kaput

Post by Thomas Okken »

HPMike wrote:
Sun Jan 16, 2022 5:01 am
What I find so mysterious is how it went from being completely bad to completely good. If this were a hard disk drive, once a portion of the surface goes bad, it remains bad forever and cannot be resurrected.
If the sector containing the root directory goes bad (i.e. what Unix calls the superblock), effectively the entire disk is hosed. In the early days of flash, this is how I tended to lose my SD cards, their contents would just appear to vanish all at once. Nowadays this is dealt with by remapping bad sectors in hardware, I believe, maybe something similar took place on your DM42 as well?
HPMike
Posts: 320
Joined: Fri Jul 21, 2017 11:01 pm
Location: DFW, Texas

Re: FAT Disk is kaput

Post by HPMike »

Well, unfortunately, the FAT disk is broken again. Michael S has offered to send me a replacement PCB. He thinks the problem is either a faulty flash memory chip or flash controller of the CPU. At least I've managed to back up all my programs to my PC and install a fresh battery in the DM42, so memory will be preserved until I am able to replace the PCB. So, I'm back to the sleeping owl off image.
Last edited by HPMike on Sun Jan 16, 2022 3:25 pm, edited 1 time in total.
DM15L, S/N 00548. DM42, SN: 00159. DM41X, SN: 00973.
HPMike
Posts: 320
Joined: Fri Jul 21, 2017 11:01 pm
Location: DFW, Texas

Re: FAT Disk is kaput

Post by HPMike »

Thomas Okken wrote:
Sun Jan 16, 2022 8:56 am
HPMike wrote:
Sun Jan 16, 2022 5:01 am
What I find so mysterious is how it went from being completely bad to completely good. If this were a hard disk drive, once a portion of the surface goes bad, it remains bad forever and cannot be resurrected.
If the sector containing the root directory goes bad (i.e. what Unix calls the superblock), effectively the entire disk is hosed. In the early days of flash, this is how I tended to lose my SD cards, their contents would just appear to vanish all at once. Nowadays this is dealt with by remapping bad sectors in hardware, I believe, maybe something similar took place on your DM42 as well?
Not in this case. It appears to be a faulty flash memory chip or flash controller of the CPU. The entire disk reports bad and it cannot be re-formatted. After seemingly being resurrected yesterday, it is now again completely broken.
DM15L, S/N 00548. DM42, SN: 00159. DM41X, SN: 00973.
HPMike
Posts: 320
Joined: Fri Jul 21, 2017 11:01 pm
Location: DFW, Texas

Re: FAT Disk is kaput

Post by HPMike »

So today, one month after reporting this problem, I received the replacement PCB, and installed it w/o any difficulty. Once I removed the old PCB it became apparent that the keyboard is an integral part of the PCB, so by replacing it I also was able to upgrade the keyboard as well. The original generation keyboard was very stiff and lacked any feel to it, whereas the new second generation keyboard is much lower effort and has a very distinct audible and tactile click to it. One thing I noticed that I was able to fully tighten the two screws holding down the PCB inside the case w/o the ENTER key sticking, whereas before it was necessary to loosen them to prevent this problem.

When I connected the calculator to my PC, I again received a message from the PC that there were problems with the drive, and it offered to correct them. Instead of letting the PC make corrections, I disconnect the FAT Disk, reformatted it from the DM42 System menu, then reconnected to the PC and it no longer reported any problems. Since this same problem occurred when I initially received my DM42, I think there must be some problem with the bulk formatting of the flash drives at the factory, which gets fixed when they are reformatted in the DM42.

After this I copied all my data from my PC to the FAT Disk, including the latest firmware version, which installed w/o a problem. I do expect that I will need to change the clock calibration factor, since this is a different RTC.

So, thanks to Michael S. for sending a new PCB to fix my DM42. :D
DM15L, S/N 00548. DM42, SN: 00159. DM41X, SN: 00973.
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