Thanks. Does the Mac Pro always use server processors on thier single processor models?
Historically speaking, Yes. But it's been a result of what's available to them, and it had to be cost effective (may not translate into cost effective for the user).
Read on...
If so, Apple will be in an odd place in Q1 of 2011. The 4-core non-server Sandy Bridge (Core i7-2600 series) will be sitting proudly in PC's, with the pressure on Apple to put them in their i-Mac's.
What you have to remember, is Intel has changed how they break down their lineup to deal with the changing market (technical reasons as well, as they've moved to increasing core counts instead of frequency).
Since 2009 (Nehalem), there's a consumer, high end enthusiast, and enterprise segment. Ultimately, this generates 3x sockets (LGA1156, LGA1366, and the LGA1567, which is the last to release). They're used for the consumer (i3, i5, and some i7 parts), enthusiast/SP Xeon (some i7 = i7-9xx, and the SP Xeons), and Mulit Processor Xeons (75xx series) respectively.
This breakdown is continuing (sockets are meant to run for 2x years), and seems to continue on yet, given the available information released so far (the actual sockets will change as needed, but retain the same 3x count/breakdown).
What this all means, is there's a divergence in the enterprise market, specifically the workstation. The SP parts have merged with the enthusiast parts. The only difference, is the ECC circuits are enabled in the Xeon variants, and disabled in the i7-9xx parts (but the circuits are still there, and the quantity pricing from Intel is the same for identical clock speeds).
If you must have more cores than an SP part can contain, you have to go with either a DP (2 sockets) or MP board (4 sockets).
What we're going to see in general, the workstation will primarily go to SP chips, as the software is well behind the hardware generally speaking (i.e. 8 cores on one die). Given the roadmaps, it appears 2013 will be the deciding year at the latest if Apple will continue with the MP or not (LightPeak plays into this, as an iMac with LP could be used as a replacement system for software development).
Now whether or not Apple will follow suit (move to the new SP processors as other vendors will), is uncertain IMO, given the cost increases resulting from Intel (no competition in the high end performance segment of enterprise parts) and Apple's idea of an acceptable margin (currently seems to be 40%). The costs have gotten high enough they've already run off most of the enthusiasts, and the independent pros are having a tough time of it (going by the various posts on MR). As per large customers (those that buy in quantity), I'm not sure if there's enough of them for Apple to continue the MP for much longer.
Apple's greed could get the better of them here, but afterall, they've gravitated to a device company already. So they may have already decided to milk it for what they can get out of it, and bail when it ceases to be profitable (i.e. sales slump to the point they can't maintain the margins currently obtained).
But if Mac Pro's only use server chips, this would mean Apple would have to stick with the 4-core Nehalem/Westmere as the base model on the Mac Pro, at least until the Sandy Bridge-EN server chip arrives Q4 of 2011. But this would mean the chip in the i-Mac would outperform the Mac Pro, and of course Apple would not let this happen.
I would suggest Apple will either delay putting the Sandy Bridge Core i7 in the iMac until the Sandy Bridge-EN arrives, or put the 4-core Sandy Bridge Core i7 in the iMacs and make the 6-core Nehalem chip their base model until the 6-core server EN-Sandy Bridge is released in Q4 of 2011.
They won't have a choice. The LGA1155 parts are consumer units, not suitable for a workstation. But they are suitable for an iMac or Mini (the main benefit for consumer Sandy Bridge is a built-in graphics processor, which Apple won't want). It's not aimed at graphics performance, but low cost systems (i.e. budget boxes that are selling like mad in developing countries such as China).
Apple will have to wait for the LGA2011 parts for the next MP, assuming they plan to produce it (seriously, not sure what will happen, as they won't break down the desktop sales by model and make it public).