Assessing IBM's POWER8, Part 1: A Low Level Look at Little Endian
by Johan De Gelas on July 21, 2016 8:45 AM ESTSystem Specs
Lastly, let's take a look at some high level specs. It is interesting to note that the IBM POWER8 inside our S812LC server is a 10-core Single Chip Module. In other words it is a single 10-core die, unlike the 10-core chip in our S822L server which was made of two 5-core dies. That should improve performance for applications that use many cores and need to synchronize, as the latency of hopping from one chip to another is tangible.
The SKU inside the S812LC is available to third parties such Supermicro and Tyan. This cheaper SKU runs at "only" 2.92 GHz, but will easily turbo to 3.5 GHz.
| Feature | IBM POWER8 (Available in LC servers) |
Intel Broadwell (Xeon E5 v4) |
| Process tech. | 22nm SOI | 14nm FinFET |
| Max clock | 2.92-3.5 GHz | 2.2-3.6 GHz |
| Max. core count Max. thread count |
10@2.92 GHz (3.5 GHz Turbo) 80 SMT |
22@2.2 GHz (2.8 GHz turbo) 44 SMT |
| TDP | 190W | 145W |
| L1-I / L1-D Cache | 32 KB/64 KB | 32 KB/32 KB |
| L2 Cache | 512 KB SRAM per core | 256 KB SRAM per core |
| L3 Cache | 8 MB eDRAM per core | 2.5 MB SRAM per core |
| L4 Cache | 16 MB eDRAM per MBC (64 MB total) |
None |
| Memory | 1 TB per socket - 32 slots (32 GB per DIMM) |
0.768 TB per socket - 12 slots (64 GB per DIMM) |
| Theoretical Memory Bandwidth | 76.8 GB/s Read 38.4 GB/s Write |
76.8 GB/s Read or Write |
| PCIe 3.0 Lanes | 32 Lanes | 40 Lanes |
The Xeon and IBM POWER8 have totally different memory subsystems. The IBM POWER8 connects to 4 "Centaur" buffer cache chips, which have each a 19.2 GB/s read and 9.6 GB/s write link to the processor, or 28.8 GB/s in total. This is a more efficient connection than the Xeon which has a simpler half-duplex connection to the RAM: it can either write with 76.8 GB/s to the 4 channels or read from the 4 channels. Considering that reads happen twice as much as writes, the IBM architecture is - in theory - better balanced and has more aggregated bandwidth.
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JohanAnandtech - Thursday, July 28, 2016 - link
Ah, you will have to wait for the improved P8 which is the first Power going after HPC :-)RISC is RISKY! - Tuesday, August 2, 2016 - link
I would support "Brutalizer". Every processor has its strength and weakness. If memory architecture is considered, for the same capacity, Intel is conjested memory, IBM is very distributed and Oracle-Sun is something in between. So Intel will always have memory B/W problem every way. IBM has memory efficiency problem. Oracle in theory doesn't have problem, but with 2 dimm per ch, that look like have problem. Oracle-Sun is for highly branched workload in the real world. Intel is for 1T/Core more of single threaded workloads and IBM is for mixed workloads with 2T-4T/Core priority. So supercomputing workloads will work fast on IBM now, compared to intel and sparc, while analytics and graph and other distributed will work faster on SPARC M7 and S7 (although S7 is resource limited). While for intel, a soft mix of applications and highly customized os is better. Leave the business decisions and the sales price. List prices are twice as much as sales price in the real world. These three processors (xeon e5v4, power8-9, sparc m7-s7) are thoroughly tuned for different work spaces with very little overlap. So there's no point in comparing them other than their specs. Its like comparing a falcon and a lion and a swordfish. Their environments are different even though all of them hunt. Thats in the real world. So benchmarks are not the real proof. We at the university of IITD have lots and lots of intel xeon e5v4, some P8 (10-15 single and dual sockets), and a very few (1-2 two socket M7 and 2 two socket S7). We run anything and every thing on any of these, we get our hands on. And this is the real world conclusion. So don't fight. Its a context centric supply.RISC is RISKY! - Tuesday, August 2, 2016 - link
of processors!rootvgnet - Friday, August 12, 2016 - link
Johan - interesting article, I enjoyed it - especially after I discovered how to get to the next page.As far as the comments go - 1) a good article will get a diverse response (from those with an open, read querying, mind.
2) I agree with those who, in other words are saying: "there is no 'one size fits all'." And my gut reaction is that you are providing a level of detail that assists in determining which platform/processor "fits my need"
Looking forward to part2.