DDD-T are the smallest right now, but will extend the workunits later this month (we think). They are still good for small computers. FAAH is also efficient and has a very tiny upload/download that minimizes connection time.

HCC is running 8 hours on fairly fast computers here, so I wouldn't go for that one. African Climate is similar for the same reason, plus it has a 10 megabyte download that will only be sent out if you have a high bandwidth connection. (It tests for that.)

HPF2 is somewhere in the middle to longer.

It looks like there could be a few new project launches this year, so I usually play with the new one for awhile and reevaluate the mix for myself each time.

Check the research area on this forum that pops up whenever a new project starts. It will not be there ahead of time but the read only area at the top of the forum usually has a mention of it also. Bugs or bad experience usually gets posted in the research area as the members get more experience with it.

I have successfully run FAAH on a 0.5Ghz computer, but anything that slow needs to run 24/7 to have a chance.

If it is still a struggle on the slowest computers, other BOINC mathematical project workunits elsewhere finish in a few seconds to less than an hour.

Chris,
Please see this post for detailed reasons why you should definitely choose DDDT for your laptop (sorry for quoting myself).

Regarding checkpoints what I have not said is that all other projects have much less checkpoints. Currently I never reach 2 minutes between two checkpoints with DDDT. For all other projects it is an average 15 minutes and up to 45 or more for projects like HPF2 for example.

Cheers. Jean.