The 49ers have signed 30-year old QB David Carr to a 2-year deal.  Carr played in 6 games for the Giants last season in which he completed 21 of 33 passes (63.6%) for 225 yards with 1 TD pass and 0 INTs (93.6 QB Rating).  He also carried the ball 9 times for 27 yards (3.0 ypc) with 1 TD run last year.  Carr has now played in 91 games in his NFL career and he has completed 1,346 of 2,251 passes (59.8%) for 14,366 yards with 65 TD passes and 70 INTs (75.2 QB Rating).  Carr has also carried the ball 302 times for 1,331 yards (4.4 ypc) with 9 TD runs in his career.  Carr might get the chance to challenge Alex Smith for the starting job in 2010 as he has a very strong arm and a lot of experience.  If nothing else Carr will likely bump Shaun Hill out of a job.