[Hardware] Notes... The case for an open client

Elektron elektron_rc5 at yahoo.ca
Wed Aug 18 13:10:24 EDT 2004


> A CRC could be used instead of a sum for the residual. The CRC 
> polynomial X^32+1 would be easy enough to implement in both hardware 
> and software and offers the same distributive properties as addition. 
> It would be nice if everyone used the same residual function but it's 
> not absolutely necessary. The residual is used for local testing and 
> random verification.

XORing is probably better than adding (except there's no carrying, so 
there's a greater chance that an error in one bit could be negated by a 
second error in the same bit). A CRC would be possible, but perhaps too 
slow, especially for software cores.

Most CPUs seem to be able to add and XOR at the same speed, though, so 
I guess the decision lies with the hardware people.

- Purr



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