Bitcoin Forum

When we switched to Crypto++ 5.6.0 SHA-256 in version 0.3.6, generation got broken on the Linux 64-bit build.  Version 0.3.8.1 is on SourceForge with the 64-bit binary updated.

Download:
http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.3.8/bitcoin-0.3.8.1-linux.tar.gz/download

Future versions after 0.3.8 will probably require SSE2.  Anyone have Pentium 3 or older where this would be a problem?

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.

IMO, SSE should be required for generation, not simply to run the client.

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)

From what I understand, removing the offending define is required only for 64-bit builds and 64-bit architectures are already guaranteed to support SSE2 instructions. 32-bit builds can retain the flag and thus continue to disable SSE2 instructions and remain compatible with older computers.

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.

Older CPU that don't support SSE2 shouldn't be excluded from coin generation in my opinion. They can still serve a vital role in block generation; I have many machines that don't support the SSE2 enhancements, but still generate blocks all the time, even if they are only churning 300-400 khash/s

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.

My impression of the difficulty was based on my broken client, haha! I've already generated a block tonight for the first time in such a long time. Having older computers generate coins doesn't seem as futile as it did earlier today. If you can keep the compatibility intact, I think it would be well worth it.

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. :)

Just to confirm -- this fix is in SVN 125?

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

Fix is in svn r124, r125 added -maxconnections.

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 think the client should have a "test coin generation" feature.  It would essentially just generate some known block just to show everything is working properly. 

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.