The newest OpenPOWER chip: A2

Besides Microwatt, another open core implementation is now available, the PowerPC A2. The chip name may not be familiar, but its most famous application should be: the Blue Gene/Q supercomputer, based on 45nm 18-core chips (16 active, one unused for yield purposes and one for interrupts, I/O and other on-chip services) at 1.6GHz with a TDP of 55W. In 2012, Blue Gene/Qs took top positions on all three major supercomputer benchmark ratings.

The A2I VHDL on offer does in fact appear to be for the Blue Gene/Q variant. This is important, because A2 doesn't have an FPU or vector unit out of the box; it leaves these to be connected through the auxiliary execution unit (AXU). The A2I BG/Q version, however, does have an IEEE 754-compliant FPU connected to the AXU, and this appears to be provided in the VHDL. There is also apparently an MMU, but while the FPU offers SIMD instructions for up to 4 double-precision floats simultaneously it is not AltiVec, so no VMX/VSX. In addition, despite being SMT-4, it is only dual issue (one instruction to the ALU, one to the AXU), and execution is strictly in-order.

A2I isn't going to replace Microwatt. Microwatt is smaller and simpler, intended for small FPGAs and embedded projects, and is actively evolving by leaps and bounds to the point it can now boot Linux. More to the point, it is intended to be fully OpenPOWER compliant. A2I, however, despite being a fully realized core, is only ISA 2.06 compliant, lacks the radix MMU, lacks AltiVec, and at least right now lacks active developers. But it's small enough that with some work and a process shrink this could be the start of a mobile OpenPOWER system: at 7nm IBM claims it got up to 3.9GHz (their blurb at right claims even higher, to 4.2GHz). And it is indeed under the OpenPOWER license.

The really interesting question is what else might show up under @openpower-cores.