POWER8 Cache: Speedy and Scalable

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IBM POWER8, which clearly stands as the best scale-out system for a business’s rapidly evolving needs, features a high-speed, scalable cache design that can rein in big data and fuel untold potential to power your analytics engine.

The result of breakthrough innovation, the POWER8 cache introduces a distinct divide-and-conquer design, which drives efficiency by allowing each core to carve out specific cache segments, while contributing to a more efficient, less costly infrastructure. 

With 96 MB of last-level cache, and double the data paths, you can now access more data faster than ever before.

Specifically, the POWER8 cache memory includes 512KB of SRAM L2 cache per core, and 96 MB of eDRAM on-chip shared L3 cache with up to 128 MB of eDRAM off-chip L4 cache per socket. POWER8 provides the capacity to feed up to 12 cores with eight threads each, for a total of 96 simultaneous, high performance computational threads in a socket.  Having enough cache to feed these threads as they crunch on data is a critical design point for the system.

Key among the sophisticated design innovations of the POWER8 cache is a memory buffer chip with 16 MB of cache. Up to eight of these chips are attached to each processor socket, yielding up to 128 MB of L4 cache. The memory buffer is named Centaur due to its dual function – half L4 cache memory and half DDR memory controller.  The design features a 9.6 GHz high-speed processor interface, with on-the-fly isolation and repair capability, and an end-to-end fast path and data retry feature to ensure lower latency.

Centaur is designed to optimize cache performance and enable memory technology innovation by separating out memory technologies from the processor. While a generic memory interface remains within the processor chip, caching structures features reside on the buffer chip that talks to the main memory – which allows for flexibility in future memory technologies. 

POWER8 systems will support a maximum of one TB of memory capacity per socket, or twice the memory capacity of the previous generation of IBM POWER7+ systems. 

Innovation is how IBM drives value to our customers. We are not in the business of designing commodity parts. POWER8 cache has set the stage for the next generation of big data and analytics.

Learn more about the unique advantages offered by Power Systems scale-out servers, in this paper written by Robert Frances Group, "The IBM Power Scale-out Advantage."