PWRficient
PWRficient is the name of a series of microprocessors designed by P.A. Semi where the PA6T-1682M was the only one that became an actual product.

PWRficient processors comply with the 64-bit Power ISA, and are designed for high performance and extreme power efficiency. The processors are highly modular and can be combined to multi-core system-on-a-chip (SoC) designs, combining CPU, northbridge, and southbridge functionality on a single processor die.

Details
The PA6T was the first and only processor core from P.A. Semi, and it was offered in two distinct lines of products, 16xxM dual core processors and 13xxM/E single core processors. The PA6T lines differed in their L2 cache size, their memory controllers, their communication functionality, and their cryptography offloading features. At one time, P.A. Semi had plans to offer parts with up to 16 cores.

The PA6T core is the first Power ISA core to be designed from scratch outside the AIM alliance (i.e. not designed by IBM, Motorola/Freescale, or Apple Inc.) in ten years. Since Texas Instruments was one of the investors in P.A. Semi, it was suggested that their fabrication plants would have been used to manufacture the PWRficient processors.

PWRficient processors were initially shipped to select customers in February 2007 and were released for worldwide sale in Q4 2007.

P.A. Semi was bought by Apple Inc. in April 2008, and closed down development of PWRficient architecture processors.  However, it will continue to manufacture, sell and support these components for the foreseeable future due to an agreement with the US Government, as the processors are used in some military applications. Some components of the P.A. Semi PWRficient were later integrated into Apple silicon processors.

Implementation

PWRficient processors comprise three parts:

CPU
PA6T
Superscalar, out-of-order 32-bit/64-bit Power ISA processor core
Adheres to the Power ISA v.2.04
Little endian or big endian operation
64/64 kB instruction and data L1 caches. 32 GB/s bandwidth.
Six execution units including a double precision FPU and Altivec unit
Hypervisor and virtualization support
Maximum 7 W at 2 GHz
11 million transistors, 10 mm² large @ 65 nm.

Memory system
CONEXIUM
 scalable cross-bar interconnect
 1–8 SMP cores
 1–2 L2 caches, 512 KB – 8 MB large. 16 GB/s bandwidth.
 1–4 1067 MHz DDR2 memory controllers. 16 GB/s bandwidth.
 64 GB/s peak bandwidth
 MOESI coherency

I/O
ENVOI
 Centralized DMA engine, 32 GB/s bandwidth
 16–64 SerDes lanes
 XAUI
 PCI Express
 SGMII
 Offload engine for cryptography, RAID, TCP

Notable users
 Curtiss-Wright will use the 1682M processor in its signal processing systems.
 Mercury Computer Systems will use the 1682M processor in its signal and image processing systems.
 NEC will use the 1682M processor in its storage array systems.
 AmigaOne X1000 uses the 1682M processor as CPU.

References

External links 

PA Semi attacks performance/Watt
FPF 2005: P.A. Semi's PA6T-1682M System on a Chip – Real World Technologies
Judicious Clocking Subdues Power-Architecture Cooling Needs – Electronic Design

Power microprocessors