The difficulty has gotten high enough that I wouldn't worry about dropping block generation support for old computers if it's hard to maintain compatibility. But the client should definitely provide some feedback explaining why the feature isn't available. Perhaps you could make a message pop up that explains why generating bitcoins is not supported on old hardware.

That's a good point, I believe you could run with generation off if you don't have SSE2.

How about add to the top of cryptopp/config.h:

#if !defined(_M_X64) && !defined(__x86_64__)
#define CRYPTOPP_DISABLE_SSE2  1
#endif

that would disable SSE2 for 32-bit builds.  (at least with GCC or MSVC)

Yes, but better have that specified in the makefile. That way anyone who doesn't care for old CPU's can compile with SSE2 support by removing the flag, without fiddling with the source.

I can also add a CMake property for that in the CMake build.

I'm still running an old node without SSE2 @600khash/s. The algorithm works so I don't see why we should make SSE2 a requirement.

Hah!  This sure helps explain a long-standing mystery.. why my 10,000 khash/sec Linux 64-bit machine is the only one that has never, in two weeks, generated a block.

You're not the only one.  I haven't generated in over a month.

SVN rev 128: disable SSE2 on 32-bit.  This may only disable it for MSVC and GCC.  Other compilers might have different 64-bit defines.

I agree. I have a second computer with which I can test difficulty 1 block generation, but I never actually do it. If there was a button to do it, I would.