# AMD Opteron Questions

## Danuvius

I have a couple of questions about AMD Opterons:

Architecture-wise are they considered x86 or amd64?  Or both?  Or something else entirely?

How well are AMD Opterons supported by the linux kernel and popular linux programs (mplayer, vmware, et al)?

If I get a two cpu slot motherboard, will it run with only a single Opteron cpu?  (allowing me to add the second one later)

How much of a difference are two cpus likely to make in a) gaming, b) video transcoding, c) general desktop-type usage?

Is there anything else I should watch out for/know about before purchasing?

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## NeddySeagoon

Danuvius,

Opterons are amd64 but they a re backwards compatible with x86.

In 32 bit mode they run all the 32 bit software. In 64 bit mode, its more complex. Some things like the windows codecs used my mplayer are not available in 64 bit code yet.  You can have a mixed 64/32 bit system though.

There are different styles of dual Opteron boards. Some  (most) have the second CPU accessing memory via the hypertransport throught the first. Other (NUMA Non Uniform Memory Architecture) give each CPU its own local memory.

I don't know of any boards that do not work with a singkle CPU.

Most games are single threaded to squeeze the best performance out of a single CPU (no wasted task switching time) so a second CPU will not be used. With transcoding, it depends if the bottleneck is CPU or memory access. You won't notice the second CPU in general destop use.

A 64 bit install is more hassel than a 32 bit one just now.

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## eelke

 *Quote:*   

> Architecture-wise are they considered x86 or amd64? Or both? Or something else entirely?

 

amd64 basically its the same chip but with more HT links allowing other connection configurations needed for multiple CPU's.

 *Quote:*   

> If I get a two cpu slot motherboard, will it run with only a single Opteron cpu? (allowing me to add the second one later)

 

Not quite sure about this it could be a problem as a single opteron system normally uses a one-way cpu (100 series) while a dual opteron requires two way cpu's (200 series). One thing I do know is that a dual cpu setup should use exactly the same CPU's. With exactly I mean not only the model number has to be the same but also stepping. So if you do not buy both CPU's directly you run a risk that you cannot buy a second CPU of the same stepping.

 *Quote:*   

> How much of a difference are two cpus likely to make in a) gaming, b) video transcoding, c) general desktop-type usage? 

 

a) Most games are not yet designed to take advantage of multiple CPU's or Dual core.

b) Depends on wether the program can distribute its load over multple threads or processes

c) For general desktop usage Opterons are overkill thought dual cpu/core systems tend to be more responsive because the chance of both core's being hogged by a process is much smaller then for a single core.

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## Danuvius

I do a lot of video transcoding with MPlayer into H.264 (via x264) format... currently on my AthlonXP I get about 10 fps.  Is this likely to improve more drastically from stepping up to a dual opteron than it would from stepping up to a singel Athlon64?

I should note that I'm asking whether someone could specifically comment on the software/codec combination.

Thanks for the other answers and tips so far!

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