Xeon chips also have extra Hardware to support Error Corrrection Code memory. So they support really big memories and you don't have to debug possible memory problems. single errors are corrected on the fly, and more complex errors halt the machine before your data get poisoned.
Xeon chips have higher-capacity I/O and are often teamed with one or more PCI slots and upgradeable and multiple graphics cards.Mac Pro (Early 2009), Mac OS X (10.6.8), & Server, PPC, & AppleTalk Printers
Xeon chips are workstation grade and therefore tend to be more reliable. when you say i7 you have to be careful as both Xeon and i7 are names that dont correlate with the actual chip unerneath.
For example, the basic i7 Macbook Pro's chip would be called an i5 if it was in a tower PC, which is technically an inferior name. A Xeon chip can be faster slower and pretty much the same as any i7, depending on the version.
What matters more is the 'architecture' which is the current design. The latest Mac Pros are 'Sandy Bridge' architecture. This is one behind the latest that Intel have. The i7 iMacs and MBPs are 'Ivy Bridge', this is the latest that Intel have and is 10% faster for every 1 Ghz given (assuming you have the same amount of cores). For reference, all other names except Haswell are older tech (Nehalem etc) and are vastly slower.
So for example, a 3.0Ghz 8 core Sandy Bridge Mac Pro is only around 1% faster than a 2.7Ghz i7 8 core Ivy Bridge iMac. You must also account for the rest of the machine though, that Mac Pro will probably have a hard drive and RAM that will run rings around the iMac in one way or another and be able to drive multiple screens and lots of other stuff out of the box as well as being more reliable.
WE have not gotten to Sandy Bridge socket, have we?
E3-12xx-series "Sandy Bridge"
The Xeon E3-12xx line of processors, introduced in April 2011, uses the Sandy Bridge chips that are also the base for the Core i3/i5/i7-2xxx and Celeron/Pentium Gxxx products using the same LGA 1155 socket, but with a different set of features disabled. Notably, the Xeon variants include support for ECC memory, VT-d and trusted execution that are not present on the consumer models, while only some Xeon E3 enable the integrated GPU that is present on Sandy Bridge. Like its Xeon 3400-series predecessors, the Xeon E3 only supports operation with a single CPU socket and is targeted at entry-level workstations and servers. The CPUID of this processor is 0206A7h, the product code is 80623.
E5-16xx/24xx/26xx/46xx-series "Sandy Bridge-EP"
The Xeon E5-16xx processors follow the previous Xeon 3500/3600-series products as the high-end single-socket platform, using the LGA 2011 package introduced with this processor. They share the Sandy Bridge-E platform with the single-socket Core i7-38xx and i7-39xx processors. The CPU chips have no integrated GPU but eight CPU cores, some of which are disabled in the entry-level products. The Xeon E5-26xx line has the same features but also enables multi-socket operation like the earlier Xeon 5000-series and Xeon 7000-series processors.
Westmere and the same old Nehalem socket, that came out debut in fall Nov 2008 used LGA1366 (same as i7-9xx)
3600/5600-series "Gulftown" & "Westmere-EP"
Gulftown or Westmere-EP, a six-core 32 nm Westmere-based processor, is the basis for the Xeon 36xx and 56xx series and the Core i7-980X. It launched in the first quarter of 2010. The 36xx-series follows the 35xx-series Bloomfield uni-processor model while the 56xx-series follows the 55xx-series Gainestown dual-processor model and both are socket compatible to their predecessors.
Why you may not find 6-core (and physical cores, not these logicall cores, heck my tablet has a processor t hat is called "4-core" but those are logical hyper-thread cores
Too much heat and watts for any iMac to have a full out 6-core. not enough air and cooling.
A single socket 2009 or '10 CAN take an i7 9xx but those are in short supple I think today, again they don;t manufacture forever though Intel does keep; Xeon longer.
A W3690 Xeon or 5600-series may not be the latest chip but it is mature, solid, has gone through revisions in stepping and firmware.
I would look at the quickpath interconnecte and how Intel has expanbded, optinuzed abd designed around some of the overhead limitations inherent in any dual or higher socket processor configurations.
You would need apps that did make good use of more than 4-cores. Was multi-threaded, not all are. 4-core wit h higher clock is probably more than enough.
The Mac Pro can have up to two optical drives and 4 hard drives installed inside of it. This can be very handy if you need fast pre and post processing of video. Thunderbolt does offer faster speeds in some situations, but being an external device, one accident, and your data transferred is lost during a drive disconnect. Better to have an accident doing a backup, than working on primary data.
That is incredibly lazy of Apple. Incredibly lazy. Update all the Mac Pro models but the base processor which most people are going to buy... And personally I'd prefer a Ivy Bridge or Haswell Xeon to a SB in the next Mac Pro.
Thanks for the heads up The Hatter and Allan.
Intel has been slow to release the Xeon chip that Apple needs for the new Mac Pro so if you are passing out blame then a fair portion of it should go in thir direction also and not just towards Apple. There is very little Apple can do if they don't have the chips.
Do a search for IB-E and SB-E was
Weak economy world wide
Takes 6 months with luck to match chips stepping firmware motherboards
Same for nVidia
New design for DDR4 too