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very low frequency tech postings  -   06 02 2007

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Tue, 06 Feb 2007

less than 42 in 1

you all know these flash-card readers which are being sold as 12-in-one readers or 23-in-one or even 42-in-one readers. I have one of these for a while now, which I had gotten from a flea market for 2 Euros. And for my new mobile phone I had gotten one of these tiny 2GB microSD cards.

The reader had worked fine with one of my old 32MB MMC cards, but not with the 2GB card. I was tempted to blame the linux kernel driver, but the investment of 20 Euros (what a fair price, I live in the jungle:) for a new reader proved it was a problem of the reader. Such a reader basically is a USB-based SPI-controller which translates host requests to SPI which the card understands. SPI itself has no addressing scheme, so the controller is to blame, having a limited address-space.

If you ever have trouble with a non-working flashcard, and find somthing like this in your logs:

kernel Initializing USB Mass Storage driver...
kernel scsi0 : SCSI emulation for USB Mass Storage devices
kernel usb-storage: device found at 3
kernel usb-storage: waiting for device to settle before scanning
kernel usbcore: registered new interface driver usb-storage
kernel USB Mass Storage support registered.
kernel scsi 0:0:0:0: Direct-Access     IC       USB Storage-CFC  301b PQ: 0 ANSI: 0 CCS
kernel scsi 0:0:0:1: Direct-Access     IC       USB Storage-SMC  301b PQ: 0 ANSI: 0 CCS
kernel scsi 0:0:0:2: Direct-Access     IC       USB Storage-MMC  301b PQ: 0 ANSI: 0 CCS
kernel scsi 0:0:0:3: Direct-Access     IC       USB Storage-MSC  301b PQ: 0 ANSI: 0 CCS
kernel usb-storage: device scan complete
kernel scsi.agent[20468]: disk at /devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2:1.0/host0/target0:0:0/0:0:0:2
kernel scsi.agent[20457]: disk at /devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2:1.0/host0/target0:0:0/0:0:0:3
kernel scsi.agent[20461]: disk at /devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2:1.0/host0/target0:0:0/0:0:0:1
kernel scsi.agent[20454]: disk at /devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2:1.0/host0/target0:0:0/0:0:0:0
kernel sd 0:0:0:0: Attached scsi removable disk sda
kernel sd 0:0:0:1: Attached scsi removable disk sdb
kernel sd 0:0:0:2: scsi: Device offlined - not ready after error recovery
kernel sdc : READ CAPACITY failed.
kernel sdc : status=0, message=00, host=1, driver=00
kernel sdc : sense not available.
kernel sdc: Write Protect is off
kernel sdc: Mode Sense: 00 00 00 00
kernel sdc: assuming drive cache: write through
kernel sd 0:0:0:2: Attached scsi removable disk sdc
kernel usb_id[20644]: usb_id: unable to access '/block/sda'
kernel usb_id[20655]: usb_id: unable to access '/block/sdc'
kernel usb_id[20684]: usb_id: unable to access '/block/sdb'
kernel scsi_id[20685]: scsi_id: unable to access '/block/sdb'
kernel scsi_id[20656]: scsi_id: unable to access '/block/sdc'
kernel scsi_id[20739]: scsi_id: unable to access '/block/sdc'
kernel scsi_id[20645]: scsi_id: unable to access '/block/sda'
kernel scsi_id[20741]: scsi_id: unable to access '/block/sda'
kernel scsi_id[20747]: scsi_id: unable to access '/block/sdb'
get a new reader. If you want warranty forever, don't buy in germany (as I did, not reading the fine print ;). Italians: leave the country! Warranty for your great grantchildren's 22 ExaByte cards is to get elsewhere.

never in italy

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harddrive on coffee

Some two weeks ago I had spilled coffee over my laptop. Not too much, but I feared the desaster and immediately turned the laptop upside-down and wiped it dry. The machine kept working and I almost forgot about it, also I don't reboot very often. Until I installed the new 2.6.20 kernel yesterday. I rebooted and the BIOS splash screen sat there unusually long while the HDD-LED was blinking wildly. The harddisk wasn't recognized anymore.
To ensure I didn't fuck up the bootloader I booted a live-CD and could confirm the harddisk was still working propperly, and the bootloader was installed correctly. So the fear of dataloss (not too much but still nasty) was gone. The biggest remaining fear was that the mainboard's HDD-controller was gone. But first I removed the harddisk and found ... coffee with sugar!



I wiped the board clean with a cloth of microfiber and distilled water. Luckily the component side had no traces of the brew. Rebooted, and the BIOS talked to the drive again. Not being a chemist I am still wondering what is so conductive in completely dried coffee with sugar?

Note to self: next time do performance tests on a harddrive on caffeine ;)

lessons learned:
  • linux still has no live kernel update
  • we're still better off drinking coffee with sugar than with salt

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