XP Pro will not boot if microdrive in cardreader

  hssutton 09:51 10 Dec 2003
Locked

Can anyone explain why my PC, XP Pro will not boot if I leave my microdrive in the cardreader, but will boot with a compactflash inserted.
A puzzle more than a problem.

Harry

  hssutton 13:36 10 Dec 2003

LeadingMNMs Thanks for the input, however the problem is nothing to do with the boot sequence. more of a problem peculiar to the microdrive.

  hssutton 19:41 10 Dec 2003

Have found the problem, there is a "Cyclic Redundancy" half way through the microdrive. Now what on earth is a "Cyclic Redundancy"

  Big Elf 19:45 10 Dec 2003

CRC or "cyclic redundancy code") A number derived from, and stored or transmitted with, a block of data in order to detect corruption. By recalculating the CRC and comparing it to the value originally transmitted, the receiver can detect some types of transmission errors.

A CRC is more complicated than a checksum. It is calculated using division either using shifts and exclusive ORs or table lookup (modulo 256 or 65536).

The CRC is "redundant" in that it adds no information. A single corrupted bit in the data will result in a one bit change in the calculated CRC but multiple corrupted bits may cancel each other out.

CRCs treat blocks of input bits as coefficient-sets for polynomials. E.g., binary 10100000 implies the polynomial: 1*x^7 + 0*x^6 + 1*x^5 + 0*x^4 + 0*x^3 + 0*x^2 + 0*x^1 + 0*x^0. This is the "message polynomial". A second polynomial, with constant coefficients, is called the "generator polynomial". This is divided into the message polynomial, giving a quotient and remainder. The coefficients of the remainder form the bits of the final CRC. So, an order-33 generator polynomial is necessary to generate a 32-bit CRC. The exact bit-set used for the generator polynomial will naturally affect the CRC that is computed.

Most CRC implementations seem to operate 8 bits at a time by building a table of 256 entries, representing all 256 possible 8-bit byte combinations, and determining the effect that each byte will have. CRCs are then computed using an input byte to select a 16- or 32-bit value from the table. This value is then used to update the CRC.

Ethernet packets have a 32-bit CRC. Many disk formats include a CRC at some level.

  Big Elf 19:47 10 Dec 2003

I'm talking about I 'borrowed' it from click here.

  hssutton 20:28 10 Dec 2003

Wow! I guess that means my microdrive is knackered.
I can still access the first 250Mb then I get the Cyclic Redundacy message. Does anyone know if this gets progressively worse.

  Big Elf 20:38 10 Dec 2003

I assume the CRC algorithm is suggesting a potential rather than an actual disc failure.

Is there a disc utility avaialable from IBM/Hitachi that allows you to run a disk check to confirm this?

Depending on the age it may still be covered by the warranty/goodwill.

  hssutton 21:08 10 Dec 2003

Thanks or the suggestion Big Elf, I will check out the IBM site

This thread is now locked and can not be replied to.

Elsewhere on IDG sites

FIFA 19 review

Game artist Elora Pautrat shows the soft side to cyberpunk in her gorgeous landscapes

iPhone XS vs iPhone X: What is the difference?

Comment faire la mise à jour d’un Mac vers macOS Mojave ?