LC-Asia: Facebook contemplates ARM servers [LWN.net]

LC-Asia: Facebook contemplates ARM servers

Posted Mar 15, 2013 17:05 UTC (Fri) by robert_s (subscriber, #42402)
In reply to: LC-Asia: Facebook contemplates ARM servers by butlerm
Parent article: LC-Asia: Facebook contemplates ARM servers

So you need 16 copies of the OS and common software in memory?

How much memory were you planning on putting on those external DIMMs?

If "a lot", how were you planning on cramming all those lanes into the single smallish SoC package?

There are of course many-many-core chips like those made by Tilera, but note these seem to use a rather exotic and, well, "different" memory architecture that can't just be cooked up by a SoC vendor "throwing on" 16 cores to a die.

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LC-Asia: Facebook contemplates ARM servers

Posted Mar 21, 2013 19:29 UTC (Thu) by dfsmith (guest, #20302) [Link]

Well, let's say there's about 100MB of system software. With the price of DDR3 at around $6/GB (http://www.dramexchange.com/), that makes it of the order 60 cents per CPU unit.

Fixing the issue to reduce system software overhead would probably cost 4 person-years; or about $1M of burdened payroll.

That makes payback at around 2 million CPU units. Feasible, but probably not cost effective. And by the time the redesign is finished, DRAM prices will have dropped again.