I've managed to set up dependencies and build bitcoin with MS Visual C++ 2008 Express Edition. I'll give 2010 a try at some time.

There is a custom allocator class in serialize.h, secure_allocator, that fails to build with non-debug runtime selected. It is my understanding allocator classes require a template copy constructor, I've attached a small patch that solves the problem.

As Satoshi noted elsewhere, the MSVC build is indeed significantly slower khash/s-wise (more than twice) than the prebuilt one (MinGW?), even though I enabled the highest optimization level options and also global optimization with link-time code generation. I find that result strange, since MSVC is not known to have significantly worse optimizer than GCC's. Most probably the problem can be traced to the sha module that is extracted from Crypto++. I find in Crypto++ SVN there are revised versions of the module, including x86/x64 assembly for SHA-256. Using the newer versions would involve reintegrating their dependencies, though. On that note, why aren't we using OpenSSL's SHA-2 hashing functions instead? Since we already use OpenSSL, this would be a better solution than to manually support a SHA module from another library.

You could try the SHA2 implementation from : http://polarssl.org/

With a simple test in Visual Studio 2008 of a busy loop executing the hash function it was able to hash at 1.5x the rate that bitcoin does.

How many bytes does bitcoin typically hash each time?

edit
It appears, if I'm looking at the source correctly, that bitcoin does 2 hashes and a bunch of other stuff and only counts it as 1 hash.  Which means polarssl probably isn't faster then.

Further examination of the source makes it clear that the hashing is done in blocks of 64 bytes.  I was able to hack the SHA256 functions from PolarSSL and got it to do the block hashing just like the current code, with about a 10% increase in speed.  I verified the hashes produced are the same.

I took the plunge and got all the dependencies together and compiled Bitcoin myself to try to get the new hashing in place.  It's odd that you say that a MSVC build decreases the hashing performance, as I've found it increases it.  I'm using Visual Studio 2008 Standard on a 32bit dual core machine, so maybe that has something to do with it.  I went from ~1000khash/sec with the build from the Bitcoin website, to ~1350khash/sec by just compiling the source with Visual Studio 2008, to ~15000khash/sec with Visual Studio 2008 using the PolarSSL hashing functions.

edit - latest binary 2010-07-22
You can get my build here : http://www.filedropper.com/bitcoin-032_3
You'll need the Visual Studio 2008 redistributable to run this, so if it crashes immediately or complains about an incorrect configuration you need to install this.  It includes the modified sources.  I used the latest bdb, which seems to update the database format, so you can't go back to the old client because it can't open the newer database.  I suggest you save your database before you try this build if you want to revert back later.

I gave it a try using the x64 Intel compiler with full optimization, performance is practically identical to the stock algorithm, in fact the new algo seems marginally worse.

It's baffling. Do you mind posting the makefile/project you used to build the original source?

bit of a shame you linked it against BerkeleyDB5, that will break everyone's database if they should wish to go back to the stock build.

Found the culprit. I had left in the  /Ob0 option from the original makefile, which obviously led to the abysmal performance I was getting. With proper settings, the VC++ build is really faster. This tinkering with makefiles is a major hassle, I'm going to suggest converting to CMake in another post.

Regarding the SHA-256 function, we can:

1) leave it as it is - requires no effort, but it seems other solutions provide significant performance benefits;

2) adopt the SHA-256 code from later releases of Crypto++; an asm version is currently available; we have the option to either extract the functionality from modules and integrate it into bitcoin source as currently done, which would not be trivial for all SHA module dependencies, or use the complete Crypto++ library as a dependency. No one has done either yet as far as I know, so it is not clear how much faster will it be. More interestingly, I've skimmed the change logs and there are various fixes in Crypto++'s sha module as well. I'm not certain if there are any serious problems with the code bitcoin is currently using though.

3) Integrate code from PolarSSL, like BlackEye did. He claims a 50% khash/s increase with that code.

If we choose either of the last two options, we need to take great care that the hashing functionality is preserved without change or breaking anything. Unit tests would greatly help here, but for that the sha-invoking code in bitcoin would need to be extracted to a separate unit which can be tested.

I could do that refactoring, create unit tests for the hashing and provide patches. Then we can more freely experiment with upgrading the sha implementation. Satoshi and/or anyone interested, post your thoughts.

Excellent work.

Can you provide patches against current SVN?

is this the x86 asm? I dumped out the x64 asm and integrated it and performance has proved to be nothing short of blistering.