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Subject: Re: Bitscan Conclusions

Author: Alessandro Damiani

Date: 11:16:08 01/06/03

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[snip]

>>Thanks for the info!
>>
>>Since some time I favoured the Athlon to the P4, but now I am disappointed. It
>>seems that the next PC I will buy will be a 64 machine....when it will be cheap
>>enough. *sigh*
>>
>>BTW do you know why AMD didn't improve their bsf/bsr to get near Intel's?
>>
>>Alessandro
>
>I don't think the Pentium 4 has the 2-cycle bsr/bsf instruction. They don't list
>it in the timing tables, so I'm not sure what the timing is. Likely they use a
>binary search like AMD does because it has uniform search time and performs
>relatively well. When they ramp the clock speed, those 8 cycles become cheaper
>and cheaper... :-)
>
>AMD did improve bsf/bsr from the K6, just not to 2-cycles. Making bsf/bsr
>extremely efficient isn't that useful because most applications can't use the
>instructions. That space/complexity is much better spent on things that benefit
>most applications which in turn will benefit Chess, too. AMD's decision makes a
>good tradeoff unless you want to build an ASIC for Chess.
>

You are right.


>BTW, since the K8 is really just a 64-bit K7, it should be in the same price
>range.
>
>-Matt

Thanks Matt! The PC-future looks bright.

Alessandro



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