Quilted Dies of CPU & RAM

[Eugen Leitl]

On Tue, Nov 14, 2006 at 05:33:09PM +0100, Dave Long wrote:

> A couple of years ago* I'd wondered about gray-coded PC increments.   

Do you know how to implement a local-bitflip (linear, or slightly
staggered registers) Gray code with the shallowest number of gates?

> Well, the DSP people haven't gone that far, but they do offer the  
> option of bit-reversed autoincrementing index registers.  By counting  
> left-to-right (x000, x100, x010, x110, x001, x101, x011, x111, x000...)  
> one can get various power-of-two circular buffers "for free".
> 
> That may seem like a lot of trouble to save a mask op, but there's a  
> good market reason to provide the feature: bit reversal simplifies  
> twiddling FFT butterflies.

This is very old (1994-1996), but you might like
http://leitl.org/oldcontent/ui22204/.html/txt/8uliw.txt

-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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