Athlon 64 FX or Dual Opteron?

[Xenophon]

I do a lot of video encoding (2 at once sometimes) as well as other
fairly heavy CPU intensive things while encoding goes on. I also do
some GPU/CPU intensive gaming like Far Cry and will likely get into
Doom III. I also use VMWare GSX a lot. I'm considering building...

2-way Opteron 242
(242 is $300 on pricewatch vs. $440 for 244. 2x244 worth the extra
$280?)
Tyan Thunder K8W (S2885)
ATI AIW 9700 Pro (already have one)
WinXP Pro and Suse Linux

What's the difference between Opteron and Athlon other than that
Althon is not SMP capable? Should I go for a single Athlon 64FX or is
dual Opteron better for doing many tasks at once, especially VMWare?
I'm thinking the latter, especially for WinXP.

Please respond to this thread and not email.

Thanks in advance.

 

[Tony Hill]

I do a lot of video encoding (2 at once sometimes) as well as other
fairly heavy CPU intensive things while encoding goes on. I also do
some GPU/CPU intensive gaming like Far Cry and will likely get into
Doom III. I also use VMWare GSX a lot. I'm considering building...

2-way Opteron 242
(242 is $300 on pricewatch vs. $440 for 244. 2x244 worth the extra
$280?)
Tyan Thunder K8W (S2885)
ATI AIW 9700 Pro (already have one)
WinXP Pro and Suse Linux

What's the difference between Opteron and Athlon other than that
Althon is not SMP capable?

The Athlon64 FX and the Opteron 14x chips are 100% identical. The
only difference between those chips and the Opteron 24x chips is that
the latter are dual capable while the former are not.

Should I go for a single Athlon 64FX or is
dual Opteron better for doing many tasks at once, especially VMWare?
I'm thinking the latter, especially for WinXP.

For multiple tasks at once, dual processors systems will almost always
be a lot better than single processor systems. I don't know how much
VMWare enters into this equation, but it supports multiple processors,
so it's almost certain to work better with two chips than just one.

Now, games are a slightly different case here. Games will almost
certainly be faster with just a single fast processor than two
slightly slower processors. Most games are not multithreaded to any
meaningful amount, and I doubt that we'll see this change for Doom III
or Far Cry (ID has made some noise about multithreading in the past,
but it hasn't lead to much actual performance).

 

[Mike Tomlinson]

The Athlon64 FX and the Opteron 14x chips are 100% identical.

Doesn't the Opteron require registered memory, whereas the A64FX will
work with cheaper unbuffered SDRAM?

 

[Derek Baker]

Doesn't the Opteron require registered memory, whereas the A64FX will
work with cheaper unbuffered SDRAM?

No. Not yet.

 

[Xenophon]

Thanks for the response. I didn't realize Althon FX was identical to
Opteron other than SMP. I thought FX had additional boosts and 64-bit
features of some sort... like a dot release or something like that.

I should have clarified my question though. For what I intend to do
below, would it be better to have a single 3000+ FX (~$800) or dual
1.6ghz Operton (~$300 ea.). Gaming may be the only reason to have a
single faster CPU but will the 1.6Ghz be enough for the most demanding
games coming up? Even though the games are not dual capable, the OS
calls and other services could go to the other CPU so there may be
some benefit with the second CPU.

If it is true that the only difference of FX and Opteron is SMP
capability, I may just go for dual Opteron.

Thanks...

 

[Xenophon]

I'm confused with the memory the Tyan s2885 requires. According to
the manual....
ftp://ftp.tyan.com/manuals/m_s2885_100.pdf

....it says it 'requires registered' memory but that it 'supports ECC'
memory.

Doing a search, it looks like the only registered memory IS ECC
memory. So I'm guessing the board requires ECC. Wonder why it
doesn't explicitly state it that way.

 

[Nate Edel]

Thanks for the response. I didn't realize Althon FX was identical to
Opteron other than SMP. I thought FX had additional boosts and 64-bit
features of some sort... like a dot release or something like that.

Caveat: the Opteron 148 and Athlon 64FX both are DDR400 fsb, while the
Opteron 140/142/144 are all DDR333; I can't recall if the 146 is available
in both DDR333 and DDR400 or if it's also DDR333 only.

below, would it be better to have a single 3000+ FX (~$800)

FX51 (2.2ghz, 1mb) -- the 3000+ is the Athlon64 non-FX, and (2ghz, 512kb,
single channel)

or dual 1.6ghz Operton (~$300 ea.).

That's a 242, and thus DDR333. Also, bear in mind that the difference
between the $600 total for hte dual 1.6s and the single FX51 will be
swallowed up by the increased cost of a dual-processor motherboard.

You might also want to consider a single Opteron 146, or Athlon 64 3200+

Both sell for around $300, and offer a very significant fraction of the
performance of an Opteron 148 or Athlon 64FX-51.

Gaming may be the only reason to have a single faster CPU but will the
1.6Ghz be enough for the most demanding games coming up?

In the very short run, a 1.6ghz should be fine, although I'd be a lot more

Even though the games are not dual capable, the OS calls and other
services could go to the other CPU so there may be some benefit with the
second CPU.

There is a general perception that there's a slight benefit, but in general
it has not been borne out in

If it is true that the only difference of FX and Opteron is SMP
capability, I may just go for dual Opteron.

That's true for the top-speed models; for the slower models, note the FSB
difference. It's probably not that significant, but it's worth considering.

 

[Nate Edel]

I'm confused with the memory the Tyan s2885 requires. According to
the manual....

...it says it 'requires registered' memory but that it 'supports ECC'
memory.

Doing a search, it looks like the only registered memory IS ECC
memory. So I'm guessing the board requires ECC. Wonder why it
doesn't explicitly state it that way.

Registered memory and ECC memory are two different things.

MOST registered memory supports ECC, but there's nothing inherently
preventing someone from manufacturing non-ECC registered memory.

 

[Tony Hill]

Doesn't the Opteron require registered memory, whereas the A64FX will
work with cheaper unbuffered SDRAM?

The current revision of the Athlon64 FX requires registered memory as
well, just like the Opteron.

In a few months time AMD plans on switching the Athlon64 FX to a
different socket (socket 939) and at that time it will work with
unregistered memory, among a few other little differences, but for now
it's the exact same chip as the Opteron.

 

[Tony Hill]

Thanks for the response. I didn't realize Althon FX was identical to
Opteron other than SMP. I thought FX had additional boosts and 64-bit
features of some sort... like a dot release or something like that.

Nope, same exact chips. There's a very minor issue where the first
revision of the Opteron (that went on sale last April) would only work
with DDR333 memory or slower, while the newer Opterons and the
Athlon64 FX work with DDR400 memory, so in that sense I suppose it is
a "dot" release, but so are the Opterons now.

I should have clarified my question though. For what I intend to do
below, would it be better to have a single 3000+ FX (~$800) or dual
1.6ghz Operton (~$300 ea.).

Well the Athlon64 FX 51 runs at 2.2GHz while the Athlon64 FX 53 runs
at 2.4GHz. There is no Athlon64 FX 3000+, I think you might be
confusing the regular Athlon64 line ($150 to $400 or so) and the
Athlon64 FX line ($700 - $800).

Gaming may be the only reason to have a
single faster CPU but will the 1.6Ghz be enough for the most demanding
games coming up?

With a fairly high-end video card, yeah it should be ok for the next
while. Most games are more dependent on the video card these days
than the processor.

Even though the games are not dual capable, the OS
calls and other services could go to the other CPU so there may be
some benefit with the second CPU.

There will be a (very) small benefit here, and things like sound are
sometimes handled by a second thread, however you also lose a little
bit of performance in a dual-processor setup for extra overhead. In
the end the small performance gains you mentioned and the extra
overhead more or less cancel each other out and you get roughly
equivalent performance to a single processor setup.

If it is true that the only difference of FX and Opteron is SMP
capability, I may just go for dual Opteron.

If you can afford it, it's a great setup!

 

[Tony Hill]

Registered memory and ECC memory are two different things.

MOST registered memory supports ECC, but there's nothing inherently
preventing someone from manufacturing non-ECC registered memory.

See, for example, the Corsair TwinX 1024-3200R memory. Registered but
non-ECC. That's the only company that jumps to mind selling non-ECC
registered memory, but it certainly is possible. This stuff should
work just fine with the Tyan board.

Unregistered/unbuffered ECC memory is also quite possible. This stuff
is actually reasonably common and most big memory companies produce
it.

So, long story short, the Tyan motherboard manual is 100% correct in
saying that it "requires" registered memory and that it "supports" ECC
memory.

 

[Nate Edel]

Nope, same exact chips. There's a very minor issue where the first
revision of the Opteron (that went on sale last April) would only work
with DDR333 memory or slower, while the newer Opterons and the
Athlon64 FX work with DDR400 memory, so in that sense I suppose it is
a "dot" release, but so are the Opterons now.

Which speeds of Opteron have been released with DDR400 support? The 148/248
are all DDR400 compatible, and I seem to recall there being both DDR333 and
DDR400 versions of the 146/246 but may be wrong. Are there now DDR400
versions of the slower Opterons?

 

[Nate Edel]

Unregistered/unbuffered ECC memory is also quite possible. This stuff is
actually reasonably common and most big memory companies produce it.

It was more common than registered, at least in low-end servers of the
pre-DDR SDRAM generations. I've put together a lot of servers using it, and
have never actually bought registered memory, although I have 2x 256mb
PC100/ECC/Registered sticks that were in a Dell I was rebuilding.

 

[Rob Stow]

A pair of four month old Opty 240's on a Tyan S2885 seems to
handle Corsair PC3200 ECC registered DIMMs just fine.

 

[Rob Stow]

I'm confused with the memory the Tyan s2885 requires. According to
the manual....
ftp://ftp.tyan.com/manuals/m_s2885_100.pdf

...it says it 'requires registered' memory but that it 'supports ECC'
memory.

I've built two systems with the S2885 and helped on
one other, and I also wished that they had explicitly
stated whether or not that it supports registered non-ECC.

However, I have tried 1 GB Corsair registered non-ECC
DIMMs with those S2885 motherboard and they did *not*
work. If I move those same DIMMs and one of the CPUs
to an Asus SK8N motherboard everything works fine, so
I'm reasonably sure it is not the fault of the RAM or
the memory controller on the processor.

Doing a search, it looks like the only registered memory IS ECC
memory. So I'm guessing the board requires ECC. Wonder why it
doesn't explicitly state it that way.

Once in a while you'll find a place that advertises
registered DIMMs without explicitly stating whether
they are ECC or not. In such situations it is always
wise to contact the vendor or manufacturer for
clarification before buying.

 

[Tony Hill]

Which speeds of Opteron have been released with DDR400 support? The 148/248
are all DDR400 compatible, and I seem to recall there being both DDR333 and
DDR400 versions of the 146/246 but may be wrong. Are there now DDR400
versions of the slower Opterons?

Yup. DDR400 support is determined by the stepping of the processor,
not the speed. All chips that are stepping C0 or later, and that's
basically all of them these days, support DDR400. In fact, pretty
much all Opterons should be stepping CG by now, though there may be
some older C0 stepping chips floating around. It's quite unlikely
that there are any of the really original B3 stepping chips left
(these are the chips that do not support DDR400), AMD stopped shipping
those back around August of last year.

 

[Mike Tomlinson]

The current revision of the Athlon64 FX requires registered memory as
well, just like the Opteron.

In a few months time AMD plans on switching the Athlon64 FX to a
different socket (socket 939) and at that time it will work with
unregistered memory, among a few other little differences, but for now
it's the exact same chip as the Opteron.

Thanks. It's tricky keeping up with all these new chip releases.

 

[Xenophon]

Thanks much all. I've decided to get 3x512MB Reg-ECC PC3200 rather
than 2x1GB ECC. I hope this memory works...

http://www.acmemicro.com/estore/merchant.ihtml?pid=1894&step=4

Man, getting memory spec'd right gets to be a bit more of a bitch
every year.

Thanks again everyone. I'm ordering the 1.5GB 2x240 Opteron Tyan
system today!

 

[by]

Thanks much all. I've decided to get 3x512MB Reg-ECC PC3200 rather

than 2x1GB ECC. I hope this memory works...
http://www.acmemicro.com/estore/merchant.ihtml?pid=1894&step=4
Man, getting memory spec'd right gets to be a bit more of a bitch every year.
... I'm ordering the 1.5GB 2x240 Opteron Tyan system today!

[1] please do not top-post ...
[2] Opterons really require DIMMs in pairs. On some motherboards a single
DIMM will work, but not you won't be getting anywhere near top speed.
Both CPU's needs to have a pair (for best results, two pairs) for the
opterons to be running at its best.

 

[Rob Stow]

Thanks much all. I've decided to get 3x512MB Reg-ECC PC3200 rather
than 2x1GB ECC. I hope this memory works...
http://www.acmemicro.com/estore/merchant.ihtml?pid=1894&step=4
Man, getting memory spec'd right gets to be a bit more of a bitch every year.
... I'm ordering the 1.5GB 2x240 Opteron Tyan system today!

[1] please do not top-post ...
[2] Opterons really require DIMMs in pairs. On some motherboards a single
DIMM will work, but not you won't be getting anywhere near top speed.
Both CPU's needs to have a pair (for best results, two pairs) for the
opterons to be running at its best.

I was wondering if he'd made a typo and intended to say ...
"I've decided to get *4*x512MB Reg-ECC PC3200 rather than 2x1GB ECC.