Re: Opinions AMD64 vs EM64T vs Itanium II

On Fri, 2006-08-25 at 17:56 -0500, Paul Krizak wrote:
> While I'm obviously a bit biased, I would definitely suggest going with 

I'm obviously equally biased and would suggest the other solution ;)

A dual Woodcrest machine just plain rocks, and anyone who reads the
independent benchmarks (either for Woodcrest or Core 2 Duo) can see
that. A kick-ass microarchitecture and a huge cache make these things
just fly!

> an Opteron-based solution.  AMD64 is the original x86-64 implementation 
> (EM64T is a clone of our architecture), and thus the linux community has 
> had more time to tweak the drivers, compilers, etc. to work with AMD64 cpus.

actually drivers are Intels strong point. Intel generally "owns" the
full platform, and provides lots of tuning, tweaking and testing on the
drivers in our boards, such as ethernet and storage. And this work goes
on all the time, so the latest RHEL has the latest tuned drivers and
hardware. If you get a motherboard with chipsets from other vendors.. it
varies. For example NVidia... there is a reverse engineered network
driver only (unless you want to go through the hell of binary only
stuff) and a SATA driver without NVidia support, so no "advanced" NCQ
features etc etc. 

Whichever CPU you decide to buy, do investigate the driver situation
closely, for example check which drivers are needed, and then check how
often these get updated in RHEL (the release notes for the various
update releases are a great resource for this).

As for compilers; RHEL4 is compiled for generic afaik, but either way
both the Opteron and Woodcrest microarchitecture can deal with just
about all code thrown at it, compilers aren't that big a deal anymore.

> Also, going with AMD chips provides a long and stable upgrade path.  You 
> can start with dual-core DDR2/667 chips in your blades, and then when 
> quad-core comes out, you'll be able to upgrade to quad-core DDR2/800+ 
> chips and stay within the same power envelope.

so I can stick a quad-core in my socket 939/940 Opteron/Athlon64? I
didn't realize that.

> 
> AMD chips scale much better past four cores than Intel's chips,

I think you meant sockets not cores.

>  due to 
> Intel sticking with the antiquated front side bus architecture,

with the bensley/woodcrest "a FSB per CPU" architecture the difference
isn't really there other than a name for a 2 socket machine. The big
difference is that AMD has the memory connected to the CPU rather than
the chipset as Intel has. This has pros and cons at the same time: Pros
are that if you use local memory, you have a lower latency. Cons are
that your system de facto is NUMA and that you get all the problems
associated with that: you only get this gain if both the kernel and the
applications are NUMA aware. The kernel mostly is, applications...
mostly not. 

>  whereas 
> AMD has high-speed HyperTransport links between each chip.  When you get 
> those big beefy 4-socket 16-core blades, rest assured that the AMD 
> variety will perform much better than an equivalent Xeon configuration, 
> even if the 2-socket/4-core performance right now favors the Intel chips.

I can agree to the part after the "even if" of course ;)


-- 
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