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Re: CRC (was Re: [f-cpu] F-CPU architecture...)

woodelf wrote:

Yann Guidon wrote:

this can be found everywhere on the net
but "really fast algos" are not so common,
the best i have found being the one in info-zip (3,75 instructions/byte with x4 unrolling)

Ok I thought that was a CRC operation for the F-cpu.

1) i don't develop F-CPU for a living (unfortunately)
2) CRC is not considered as an instruction for F-CPU
(there are too many versions, so that would be very troublesome for no almost benefit)
However, putting a CRC32 in the "DMA/blitter engine" would be way cool
(that would require a 32-bit field in the block descriptor with additional flags
like "set/verify"; "irq on error", "valid/invalid CRC" etc.)

Just remember you need to calculate a 16 bit look up table.
C is great for that. :)

i start with C and test it against all derived versions.

However, my application needs CRC16 so i can't simply copy-paste info-zip's source code.
but don't worry for me, i'm not too bad in asm programming.

Better than 8088 asm programing. :(

fortunately, the i386 has brought in some nice features in the middle of the crap.

I did this years ago with 8 bit CRC ??? with refernce from BYTE.

8 bits would be too little for a 4KB block. OTOH 32bits is too much compared to the overhead and the expected error rate.



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