AM3+ is a modification of the AM3 Socket designed for CPUs which use the AMD Bulldozer microarchitecture and retains compatibility with AM3 processors. The Vishera line of AMD CPUs also all use Socket AM3+.
The AM3+ Socket specification contains a few noteworthy design changes over its AM3 predecessor. The 942 pin count for the AM3+ is an increase of one compared to the AM3 Socket layout. The AM3+ Socket has larger pin socket diameter of 0.51 mm compared to 0.45 mm with the AM3 Socket. There is a faster serial link of 3400 kHz from the CPU to the power controller, compared to 400 kHz. The AM3+ Socket offers improved power regulation and power quality specifications, including an increased maximum current support of 145 A versus 110 A. There is also a redesigned CPU cooler retention harness allowing for slightly better airflow for CPU cooling, while retaining cooler backward compatibility.
Some manufacturers have brought AM3+ support to some of their AM3 motherboards via a simple BIOS upgrade. Mechanical compatibility has been confirmed and it's possible for AM3+ CPUs to fit in AM3 boards, provided they can supply enough peak current. Another issue is the use of the sideband temperature sensor interface for reading the temperature from the CPU. Therefore, some CPU PWM fan pins may only run at full speed. Also, certain power-saving features may not work, due to lack of support for rapid VCore switching.