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Subject: Re: Question to Dr. Robert Hyatt

Author: Vincent Lejeune

Date: 12:06:54 05/20/03

Go up one level in this thread


On May 20, 2003 at 14:05:18, Tom Kerrigan wrote:

>On May 19, 2003 at 21:43:03, Matthew White wrote:
>
>>On May 19, 2003 at 17:18:13, Tom Kerrigan wrote:
>>
>>>On May 18, 2003 at 12:29:33, Ricardo Gibert wrote:
>>>
>>>>On May 18, 2003 at 09:40:34, Alvaro Jose Povoa Cardoso wrote:
>>>>
>>>>>Hi, I was thinking on upgrading my system to an Athlon 64 (not yet released) by
>>>>>Christmas 2003.
>>>>>Assuming those systems will be available by year end, I was wondering if by then
>>>>>you will have a binary of crafty that would run 64 bit instructions and if it
>>>>>would run normaly with winboard.
>>>>>Also, will it run on the current Windows XP (32 bit)?
>>>>>
>>>>>
>>>>>Best regards,
>>>>>Alvaro Cardoso
>>>>
>>>>Don't be so eager to jump on the athlon 64 bandwagon. Too many things are new
>>>>about it:
>>>>
>>>>(1) New 64 bit cpu
>>>>(2) New supporting chipsets
>>>>(3) New 64 bit OS
>>>>(4) New hardware drivers
>>>>(5) New 64 bit compilers
>>>>(6) and more generally: New 64 bit software
>>>
>>>If you don't like (3), (4), (5), or (6), then just use 32-bit software.
>>>
>>>Reviews of Opteron running 32-bit software indicate that it performs quite well.
>>>
>>>Speaking to each point individually:
>>>
>>>(1) - What's wrong with a new processor? Would you hold off on buying a Pentium
>>>5 because it's new? What would you wait for, a Pentium 6 instead? Besides, the
>>>Athlon 64/Opteron is based on current Athlons, so it's not 100% new.
>>>
>>The Pentiums were based on the 486's, but that didn't save them from the "F00F"
>>bug. Some people don't mind buying processors with low serial numbers, others
>>do. It's a matter of personal preference, I guess.
>>
>>Matt
>
>I wasn't aware that the Pentium borrowed anything from the 486, and if it did,
>it must have been a very small amount.

it was an evolution of the '486

http://www.pcguide.com/ref/cpu/fam/g5P54-c.html

Superscalar Architecture: The Pentium is the first superscalar processor; it
uses two parallel execution units. Some people have likened the Pentium to being
a pair of 486s in the same chip for this reason, though this really isn't
totally accurate. It is really only partially superscalar because the second
execution unit doesn't have all the capabilities of the first; some instructions
won't run in the second pipeline. In order to take advantage of the dual
pipelines, code must be optimized to arrange the instructions in a way that will
let both pipelines run at the same time. This is why you sometimes see reference
to "Pentium optimization". Regardless, the performance is much higher than the
single pipeline of the 486.

Wider Data Bus: The Pentium's data bus is doubled to 64 bits, providing double
the bandwidth for transfers to and from memory.

Much Faster Memory Bus: Most Pentiums run on 60 or 66 MHz system buses; most
486s run on 33 MHz system buses. This greatly improves performance. Pentium
motherboards also incorporate other performance-enhancing features, such as
pipelined burst cache. The Pentium processor was also the first specifically
designed to work with the (then new) PCI bus.

Branch Prediction: The Pentium uses branch prediction to prevent pipeline stalls
when branches are encountered.

Integrated Power Management: All Pentiums have built in SMM power management
(optional on most of the 486s).

Split Level 1 Cache: The Pentium uses a split level 1 cache, 8 KB each for data
and instructions. The cache was split so that the data and instruction caches
could be individually tuned for their specific use.

Improved Floating Point Unit: The floating point unit of the Pentium is
significantly faster than that of the 486.




>
>If you're running a server, I can see why you'd want to avoid F00F-style
>situations, but the worst a processor bug can do to Joe Sixpack is cause his
>computer to crash, and even that isn't so likely considering the millions of
>hours of testing these designs go through.
>
>-Tom



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