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Re: Why do I need an AMD64?



Eric Lacroix wrote:

Le ven 01/10/2004 à 17:00, Jérôme Marant a écrit :
I'm pondering buying an Athlon64 machine. However, I wonder why
I would need a 64 bits machine.

Well, for most of my use, a PentiumII class machine does what I need so I rarely need an AMD64 either. Why do I have the hardware and why am I running Debian/Sid/amd64 on it ?
(a)  Sometimes I do need a more powerful computer for various things, and
(b)  Application complexity is comfortably keeping up with Moore's law, so
(c) Within the lifespan of this machine I will routinely need the performance.

Or, to put it another way: While I can make do with a PentiumII right now, we have to look at when I purchased that machine. Back then, a 486 did everything I needed, so you might argue that the logical thing to do would have been to buy a 486. However, had I done that, I'd have had to upgrade to another computer in the intervening years. Choosing the faster computer was future proofing the investment in installing and configuring my personal environment onto the PII (Debian Hamm as I recall).

Are there any reasons not to stick to 32 bits currently?

First, even if you prefer to stay 32 bits right now, I still recommend picking a 64 bit processor and running it in 32 bit mode. That gives you the option of switching over in the next year or two as your needs grow ... without building a whole new chassis.

Second, AMD64 hardware gives you four specific features ... all of which are apparent in benchmarks:
* More FP registers, which speeds up computation intensive applications
* Lower latency to main memory, which speeds up memory intensive applications * Larger virtual address space, which speeds up database and engineering applications * Larger pointers, which slows down dynamic data structure intensive applications by 3% The increases caused by the first three bullets usually compensate for the last bullet ... sometimes dramatically.

Third, given there is negligible performance downside for AMD64 use, you have to decide whether it is more painful to install AMD64 right now and get the driver/app issues resolved once, or to have to do two installs on one computer with the second one being when you decide to go to 64 bit operation in a year or two. Hope that helps.

My 2 cents (and 1st post to the list),
Eric.

Welcome.



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