Please can somebody explain what the difference is between a Xeon CPU (that has dual cores) and a Core-Duo? Also why clock speeds of new CPUs are half that of the previous generation?
I have a dual 3.0GHz Xeon workstation, the latest models have dual 2.0GHz Xeons - how is that better?! I'm rather confused and no doubt there is a simple explanation...
Well the first point that you have raised which is "Difference between a Xeon CPU (that has dual cores) and a Core-Duo." Let me put the answer in very simple words,
As you must be knowing that Xeon brand refers to many families of Intel's x86 multiprocessing CPUs while Intel Core Duo brand consists of two cores on one die, a 2MB L2 cache shared by both cores, and an arbiter bus that controls both L2 cache and FSB access. But when merging the two which gives us Intel Dual-Core Xeon ... a Xeon processor with 2 cores based on Core Microarchitecture, each core having a 2MB L2 cache (2MB per core) meaning;
Improved performance for highly multithreaded and compute-intensive applications
Low power consumption
Increased lexibility and the performance
and since there are two interconnected processors packaged as a single die (piece) silicon chip, they give more performance as compared to an older Xeon that had only one processor.
Second "Clock Speeds are half that of the previous generation". Yet again, since the dual-core technology is about confining multiple processors, this means reduced distance between the millions of transistors reducing it from 90 to 65 and yet to 45nm. So initially whenever a processor is released, you will see that the clock speed is increased gradually as processor goes through all the tests and approved to work properly. If you look up the Dual Core Xeons, you will find that the frequency varies from 1.60GHz to 3.73GHz (please find attached Dual Core Xeons list) which I suppose is pretty fast. Imagine a Xeon processor working at 3.73GHz x 2 frequency, I suppose you wouldn't want to call it slow. Also note that some Xeons have cache size of 6, 8 and even 16MB while the manufacturing technology is varying from 90 to 45nm and bus size varying from 667MHz to 1600MHz.
Now with reference to this and your third concern "Dual 3.0GHz Xeon workstation and dual 2.0GHz Xeons - how is that better?" ... let us look up the last paragraph where I just explained the concept of confining two processors as a single die, let us do a simple exercise.
Take an older generation Uni Core Xeon say 3.2GHz based on 90nm manufacturing technology, a bus size of 533MHz and 4MB cache and match it's performance with a Dual-Core Xeon say, 2.33GHz based on 45nm Mfg. technology, a bus size of 1333MHz and 6MB Cache (Model: SLANF). Now when you do benchmarking, the newer Dual-core Xeon (Dual Core 2.33GHz) will simply outclass your older Xeon (Uni-Core 3.2GHz) though the newer Xeon appears to quite low in frequency as compared to the older Xeon but the fact is that the newer Dual-Core Xeon operated at a frequency of 2.33GHz x 2 = 4.66GHz while your older Xeon operated at 3.2GHz x 1= 3.2GHz. Frequency here was not the only elements but the other factors that I have listed.
Moreover, as you must have read and experienced, we now have Quad-Core Xeons meaning 'Four Cores' and imagine how well your system would perform with 4 processors packed and working as a single die.
To be honest, all this is a very long discussion and I have tried to summarize all this as much as I could however I feel that you need to study over the following before you start digging deep into Dual and Quad Core Xeons.
http://en.wikipedia.org/wiki/Intel_Core_microarchitecture Intel Core Microarchitecture
http://en.wikipedia.org/wiki/Xeon Intel Xeon
http://www.intel.com/technology/computing/dual-core/index.htm?iid=tech_as+multi_dual Intel Dual Core Technology
http://en.wikipedia.org/wiki/Intel_Core_2 Intel Core 2
http://www.intel.com/technology/quad-core/index.htm?iid=tech_mc+quad_head Intel Quad Core Technology
http://www.intel.com/multi-core/index.htm?iid=tech_as+multi_more Intel Multi Core Technology
Hope this all helps though the answers could have been very short but I felt a more detailed elaboration was required and I tried to be short and precise as much as possible. However if you still feel that you missed something, do let us know and we will be glad to provide you detailed support and information.
Very nice answer Javed. Taking this question further. Why should a customer by core duo qud instead of xenon quad processor for desktop applications? Also will operating systems like Vista 64 behave differently on both?