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Intel Lindenhurst Xeon DP Platform Discussion
Steve from Hexus writes "Hexus.net has a article looking at Intel's latest Xeon platform: Lindenhurst, discussing the Paxville dual-core processor, E7520 core-logic, where it could go right for Intel, and where it could all go wrong." From the article: "If you're I/O bound by your threads in any way, you can hit problems (all threads touch the MCH, then there's a 266MiB/sec bus link to the I/O processors to cross, then the data hits disks or network hardware). If you're memory subsystem bound in any way, especially on a majority of compute threads, performance is likely gone. There's just too much resource sharing for it to all conceivably work well, especially compared to Opteron. I can forsee many a scenario where dual-core Opteron will give Paxville Xeon DP a beating."
I've thought the same. I have racks of single core 3.0 GHz Xeons that strain the memory bus to the limit. Adding more cores to that mix is a waste. So, the new cluster is dual-core AMDs. The Intel architecture is generally good for the codes that we run, but I couldn't justify not buying AMDs. Price, thermal footprint, and performance all went that way.
Protip to Intel: Stop trying to feed your users this crap.
For a single CPU, the quad piped 200Mhz FSB does fine. It can fully utilize two channels of DDR 400 RAM, which is the standard on the better desktop mainboards. A single AMD CPU does not better.
Things are different with multiprocessor setups:
Here each Opteron has its own memory interface, while the Xeons have to share one FSB. As a result, the total Opteron memory bandwith is proportional to the number of sockets. Total Xeon bandwith does not grow with more sockets.
This does show up heavily in reviews of 2-processor machines, expect it to be worse in 4- and 8-way-systems.
C - the footgun of programming languages
Wow - that's a *LOT* of Tommy Lee Joneses and Will Smiths!
:-)
Looking past the joke, for anyone who may be wondering why that 'i' is there, they're just being accurate. "MiB" is the abbreviation for "mebibyte", which is 2^20 bytes. The more "common" notation, "MB", is the abbreviation for "megabyte", which is 10^6 bytes.
The terms "gibibyte", "mebibyte", "kibibyte", etc. were defined in 1998 by the IEC to disambiguate "megabyte", etc. The "giga", "mega", "kilo" prefixes from the SI units have always referred to powers of 10. With the advent of computers, it became convenient to use them to refer to powers of two that are close to powers of 10. So, "kilo" was used to mean 1024, "mega" was used to mean 1048576 and "giga" was used for 1073741824. The context was generally sufficient to disambiguate those usages from the standard powers-of-ten usages. Basically, everyone figured that if you were talking about computers, the prefixes referred to powers of two.
But there are plenty of computer-related contexts where the prefixes have their traditional meanings. Hard disk drive storage sizes, for example, are measured with powers of 10 by drive manufacturers, but file systems generally use binary prefixes This is why your 80GB drive shows up as only 74.5GB "formatted". It's not that lots of space is wasted by the formatting; the issue is that 80*10^9/2^30=74.5. The two measurements are using different units. Data rates are also traditionally specified in powers of 10. RAM sizes are powers of two.
So, to disambiguate the prefixes while not disturbing the traditional meanings, the IEC coined a new set of binary prefixes, along with corresponding abbreviations. The new prefixes all end in "bi", for "binary".
Note to ACs: I usually delete AC replies without reading them. If you want to talk to me, log in.
Except the Alpha was a RISC processor (and a pretty clean one at that), so its short pipelines didn't lose as much performance to branch miss-predictions as the P4/Netburst does. IIRC, both the P4 and Athlon CPU's had to get up to around 1.4-1.5GHz before they beat the performance of the 800MHz 21264, the last and fastest Alpha produced. *sigh*