Is there any server solution out there that provides four intel processor with a minimum of 2,8Ghz clock speed? I can't seem to find this configuration anywhere. Is there any documentation that explains why this configuration is impossible / doesn't exists?
Make sure your client understands what they are asking for. It's very easy to find systems that match the specs you have given above, but almost certainly will be something they are quite unhappy with.
Is your client aware that when Intel went to the Core architecture they increased the amount of work that can be done per clock, and reduced the clocks? I say this because of your saying "minimum of 2.8GHz". 2.8GHz is basically the top end of server CPUs if you're buying new (above it they have 2.93, 3.2, and 3.33GHz, looking at NewEgg's Intel server CPU section). These CPUs alone start at $1,300 each
A couple of years ago 2.8GHz was quite common in the P4 architecture. With the Core architecture, you would get around the same amount of work done in a 1.8GHz CPU was P4 could in a 2.8.
So, your client may be asking based on old data. In which case it's easy to satisfy. Look on ebay, there are quite a few of these old servers available, I see a Dell Poweredge 6650 with quad 2.8GHz CPUs listed for $89.99 and 0 bids. Before you get it though, realize that you'll be lucky if you can get two of these on a single 120V power circuit, it's going to cost a LOT to run.
If your client has code that isn't really able to be multi-threaded, and just needs to have the highest possible clocks, look at a Core i5 system where you can get dual cores at 3.6GHz fairly inexpensively (around $1,500 for a server-class system). If they really need 4 execution cores, you can get a Core i7 with 3.33GHz for around $2,500. That's a single socket, but 4 execution cores.
If they really need 4 discrete CPUs (meaning 4 sockets), do they realize they're looking at probably 16 to 32 cores and prices starting at $15,000? You just aren't going to get 2.8GHz in that though. For example, the Supermicro 8026B-6RF system has 4 sockets for Intel 75xx series CPUs which newegg is only listing a 2GHz 6 or 8 core CPU (for $3,000 each).
Again, make sure your client understands what they are asking for.
We've just ordered two Dell M910 blades with 4x Xeon X7560. That's Octo-Core 2.26Ghz. They cost close to 6 figures each and are the fastest Intel processors available on the market today.
There is SO MUCH more to a processor than just clock speed. If I took just four of those 2.26Ghz cores and put them against a quad-socket P4 generation 2.8Ghz server I would expect that my 2.26's would shit all over the 2.8's.
You can't just look at the raw clock speed any more, which is why Intel and AMD have dropped the clock speed from the processor names entirely. They're just not relevant.
One explanation is that servers are measured more by reliability than performance.
Therefore the fastest server on the market will not be as fast (in terms of clock speed) as the fastest workstation. Servers undergo a far longer life cycle in terms of testing, certification and support. Workstations only concern performance, and therefore can be produced faster.
Also bear in mind that processors have multiple cores these days, so a four CPU motherboard with Xeon will actually yield 16 cores.
Traditionally there has been very few and expensive boards with more than two sockets for Intel chips, because the FSB architecture didn't support it directly. The only exceptions were very expensive boards with specialized chipsets.
AMD-based boards, OTOH, have been not-so-hard to find with 4 or even 8 sockets, because the hypertransport architecture makes it so (comparatively) easy.
Current Intel processors have a AMD-like architecture; but still have limited number of inter-processor ports, so you have to be sure what exact chip model you have (and corresponding price points). Add to that the lots of cores you get on each socket, and it's understandable why there are so few many-socket boards there. In fact, it's increasingly rare to find AMD boards with 4 sockets.
Obviously everyone else has discussed how your customer has probably made some odd assumptions but if they insist on a 4 socket Intel server then they'll be out of luck with current processors as the fastest 'stock' Xeon-EX chip (X7542) only goes to 2.67Ghz, it's a 6 core bin without HT but it is their faster MP part. It can be bought in HP's DL580 G7 and similar models from Dell/IBM etc.
i know only 2 procesor motherboard
Use two i7 procesor