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I'm a bit confused as to whether this is a similar thing to having two processors, just in the one chip, or whether it's more to do with power consumption and clock speed? i.e. is a 2.8ghz Dual Core proc actually running at 1.4ghz, but giving the same MIPS performance with a much reduced power overhead?
What should this mean to me as a webmaster concerned with hosting his sites? I've seen a few offers in the last few weeks of servers with dual core processors, but without understanding the benefits that these are likely to offer, it's hard to compare prices to a traditional dual processor box. Power consumption is not my concern as I don't foot the electricity bills ;)
Do the latest versions of "standard" Linus hosting OS's and software (Red Hat/Fedora/Debian & Apache/PHP/MySQL etc) make use of these new hardware technologies? Any measurable/noticeable performance benefits?
I haven't seen too many people moving to dual cores yet on the linux front, but on the Windows side, they can't make enough, especially for DB servers. If you have something like a HP DL585, with 4 processors running Windows 2003 and MS SQL Server, you're already looking at over $100,000k just in software licensing. If you outgrew this server and had to move up to an 8way server, you're now talking over a quarter million dollars before the server even handles one request.
With dual cores, you get to keep the same number of physical chips(4), and same 4way licensing costs, but run it at 8way speeds.
With the new site I"m getting ready to release, I bought a DB server capable of utilizing dual cores, but won't purchase them until necessary. As it stands, a dual processor box can handle a few hundred requests per second as it is :)
You are going to see more and more of this. It's a BIG win, power-wise. (Most designs use no more power for two processors than their predecessors did for one - in some cases even LESS.)
The industry sees the writing on the wall that Moore's Law is petering-out. Two data-points:
- AMD is phasing out single-core processors
- Game makers are finally re-writing their code to take advantage of multiple threads
I feel that AMD is currently the King of dual-core. Take a good look at AMD before you settle on Intel.
Intel has some really cheap dual-core processors, though, that you can just drop into a Pentium socket and upgrade an existing system. (You can also do this with most AMD Socket 939 systems. However - less cheap.)
There are certain high-end server motherboards that have memory banks attached to each CPU chip (but not each core witin a chip). Each CPU chip can access all memory, but it is faster to access the memory that is attached to the CPU chip. (The OS keeps track of this, and tries to run threads on each CPU that reside in the locally-attached memory.) On these motherboards, it's advantageous to have a minimum of 4 RAM sticks - i.e. assuming dual-channel memory, you would put two sticks in the banks for each of two CPU chips. So, in that particular case there is a memory requirement, but it's not for a specific amount - just the way it is distributed. This won't come up with most home systems.
would a CPU-bound linux MySQL box benefit from having a dual-core proc over a single-core proc, all else being equal?
Oh, yes. Please don't be conned by the erroneous old saw that most applications don't use multiple threads. First of all, if that's ever been true in the last 5-10 years, it's only been true for Windows workstations - certainly not for Linux servers. Apache and MySQL both make use of multiple threads, and a busy web server can easily make use of all the CPU cores you can throw at it. A busy webserver (and particularly one hosting multiple sites) is probably one of the very best usage cases for multiple cores.