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Facebook Announces Yosemite, the First Open Source Modular Chassis for

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Facebook began experimenting with SoCs roughly two years ago when they were mostly lightweight, focusing on small cores using low power (the majority were less than 30W). Facebook indicates that their first approach was to pack up to 36 SoCs inside a 2U enclosure, allowing upwards of 540 SoCs per rack. This method did not pan out for Facebook, as the single-thread performance was too low, which resulted in high latency issues on their web platform. As such, the company then focused on higher-power processors all the while sustaining the modular SoC approach.

Facebook Announces Yosemite, the First Open Source Modular Chassis for High-Powered Microservers

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Wouldn't SO-DIMMs have made more sense for the higher densities they offer?


And, is this a misprint, or are they withholding the details?

"multiple memory channels with standard DDR DIMM slots"


/s/ Paul

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SO-Dimms generally cost more so they might have been weighing the benefits of additional memory with additional cost per node. Also DDR was referenced, although not what generation they used.

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Good point, Kevin. To back up your point, I contacted I'M Intelligent Memory yesterday

about their 16GB SO-DIMM module, and the prices are quite high. There is also a very

interesting problem being raised by these DIMMs, quoting now from:

"- To be exact, the problem for most Intel systems is not related to the capacity of 16GB, but to the fact that unbuffered DIMMs and SO-DIMMs with 16GB are built of DRAM-chips having a capacity of 8 Gigabit. As of now, Intel only added the support for 8Gb components to their Atom C2000 series processors, codenamed 'Avoton' and 'Rangeley'. For all other Intel processors, the datasheets today only show a support for max 4Gb per memory-IC. Interesting enough, older datasheets showed 8Gb, but have then be revised to a maximum of 4Gb.

"The company ASUS has modified the memory-reference-code (MRC) inside the BIOS to support 8Gb components for all their X79 chipset based boards and the 16GB modules worked fine. The BIOS-update for their X79 boards is available on the ASUS support website. Until today, ASUS still is the only company able to support 16GB modules with standard Intel processors on their X79 boards. This example from ASUS shows that the issue is mainly software related, but so far, Intel has not decided to officially support 8Gb components / 16GB modules on their processors by releasing such software-updates - except for the Atom C2000 series."

One discussion thread I followed yesterday, I think it was at, theorized that Intel did this

intentionally -- quite possibly to prevent erosion of Intel's Xeon sales.

On the other hand, the last 40+ years of computer technology have repeated the

same pattern over and over -- popular electronic components inevitably fall in price

as the manufacturing volume increases e.g. look at what happened to DVD optical drives!

Same thing has happened with DRAM: we paid over $700 for a "matched quad" of

Corsair DDR2-800, in order to build a high-performance workstation with a 12GB ramdisk,

leaving 4GB for XP/Pro 32-bit version. Now, 2 x DDR3 @ 8GB are averaging less than $200 at Newegg:

e.g. G.SKILL $108.

If I had been the decisionmaker at Facebook, I would have "made a market"

for high-density SO-DIMMs with mid-range performance e.g. DDR3-1333 or DDR3-1600,

and negotiated a huge volume discount from a capable supplier like I'M Intelligent Memory.

If I didn't have an immediate need for some large chunk of that volume order,

I'd sell the extras at cost, or marginal profit to recoup overhead.

Also, the extra "real estate" the SO-DIMMs made possible on the printed circuit board,

would leave room for some other interesting options, e.g. NV-SODIMMs using

the super-capacitor solution developed by AgigA Tech:

(As you might surmise, I have a professional interest in the future of Non-Volatile SO-DIMMs.)

Am I not correct: DDR3-1600 x 8 = 12,800 Megabytes per second raw bandwidth at the edge connector?

I appreciate your reply, Kevin. Many thanks!

p.s. I LUV your website. I visit it almost every day.


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