[Hardware] The market of ASICs (One GigaKey / Second?)

Dan Oetting dan_oetting at uswest.net
Mon Aug 9 20:14:53 EDT 2004


On Aug 9, 2004, at 2:49 PM, Elektron wrote:

> The AltiVec cores are more interesting, but completely over my head 
> (so are the integer calculations which somehow go with it). I'm not 
> sure why you can't do 5 keys at a time either (since if everything's a 
> vector, you can do some scalar things too).

I do.

But you can't just process an integer key in parallel with the vector 
keys. What you can do is get a head start by processing the first few 
stages of 4 parallel keys in the integer unit then transfer the work to 
the vector unit to finish them off. The whole thing gets wrapped around 
itself so the integer processing takes place in the dispatch holes of 
the vector work.

Here is one written for the 7400 PowerPC. The main loop is indented to 
show the separate code streams. 
<http://www.users.qwest.net/%7Eoetting/RC5testbench/AltiVec/rc5loop.s>

Some day I may have to get back into this. The benchmarks produced for 
the G5 look a little on the slow side. But it's all on the back burner 
because I can't convince myself that RC5-72 is worth pursuing. Without 
a major breakthrough the time to crack the code can simply be 
extrapolated from the previous results. And the cost for the 
electricity to run the CPUs alone is orders of magnitude greater than 
the reword.



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