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Old 16th May 2008
yurtesen yurtesen is offline
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Join Date: May 2008
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I have asked to freebsd-stable list as well. I am waiting if somebody replies or not.

I am sorry but where do you get this information about one should use more than 4GB ram with 64bit OSes? I do not want to upset anybody here but you might want to check on your resources twice.

The registers work independent from the main memory. A register is the fastest piece of memory available in the computer and processor can only operate on data which is in a register. If you have more registers for usage, you do not have to move data so frequently between slow main memory and registers (which can take several clock cycles) and you can save tremendous amount of processing time if you have a program which operates on same variables very often as you will have more spare registers to keep the data in. You will have advantages whether you use 1gb of memory or 3gb of memory or more.

As examples to irrelevance of the memory amount in a system and 64bit os usage, there have been many 64bit ultrasparc computers with as low as 128mbyte memory as well as a lot of 64bit processors routers use 128mb-256mb memory. The efficiency of using 64bit processor is independent of the memory amount installed on the system.

The fact that 32bit systems can not directly address memory over 4gb means that you must use a 64bit OS to effectively use memory in systems which has more than 4GB of memory. But there is no reason to use a 32bit OS because you have less than 4GB memory.

There are more advantages of using 64bit OS other than the speed gains, a machine owner with a machine with 2gb of ram all of a sudden might decide to upgrade to 8gb of ram. Currently there is no way to upgrade FreeBSD 32bit to FreeBSD 64bit.

As well as if one is using prebuilt packages on an i386 box then they are not using all the advantages that the current processors provide like SSE functions or some other internal processor functions. This is because prebuilt packages should be compatible with a wide range of processors as low as 486 processors, so you are effectively not using any functions added to processor since 486 processors. However if you are using a 64bit OS, as this architecture is very new, all 64bit CPUs (supporting amd64 codeset) for sure support many current functions where the compilers already know that these processors for sure support these functions thus use these advanced functions while compiling a program for 64bit platform.

Long story short, it is always advantageous to use a 64bit OS if the processor is supporting 64bit independent of the amount of memory installed.

Thanks,
Evren
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