Cray XMT

Cray XMT
DesignerCray
Bits64-bit
Introduced2005
Version3rd generation of Tera MTA
EndiannessBig-endian
PredecessorCray MTA-2
SuccessorCray XMT2
Registers
32 general-purpose per stream (4096 per CPU)
8 target per stream (1024 per CPU)

Cray XMT (Cray eXtreme MultiThreading,[1] codenamed Eldorado[2]) is a scalable multithreaded shared memory supercomputer architecture by Cray, based on the third generation of the Tera MTA architecture, targeted at large graph problems (e.g. semantic databases, big data, pattern matching).[3][4][5] Presented in 2005, it supersedes the earlier unsuccessful Cray MTA-2. It uses the Threadstorm3 CPUs inside Cray XT3 blades. Designed to make use of commodity parts and existing subsystems for other commercial systems, it alleviated the shortcomings of Cray MTA-2's high cost of fully custom manufacture and support.[2] It brought various substantial improvements over Cray MTA-2, most notably nearly tripling the peak performance, and vastly increased maximum CPU count to 8,192 and maximum memory to 128 TB, with a data TLB of maximal 512 TB.[2][3]

Cray XMT uses a scrambled[3] content-addressable memory[6] model on DDR1 ECC modules to implicitly load-balance memory access across the whole shared global address space of the system.[5] Use of 4 additional Extended Memory Semantics bits (full/empty, forwarding and 2 trap bits) per 64-bit memory word enables lightweight, fine-grained synchronization on all memory.[7] There are no hardware interrupts and hardware threads are allocated by an instruction, not the OS.[5][7]

Front-end (login, I/O, and other service nodes, utilizing AMD Opteron processors and running SLES Linux) and back-end (compute nodes, utilizing Threadstorm3 processors and running MTK, a simple BSD Unix-based microkernel[3]) communicate through the LUC (Lightweight User Communication) interface, a RPC-style bidirectional client/server interface.[1][5]

  1. ^ a b "Why is uRiKA So Fast on Graph-Oriented Queries?". YarcData Blog. November 14, 2012. Archived from the original on February 14, 2015.
  2. ^ a b c Feo, John; Harper, David; Kahan, Simon; Konecny, Petr (2005). "Eldorado". Proceedings of the 2nd conference on Computing frontiers - CF '05. Ischia, Italy: ACM Press. p. 28. doi:10.1145/1062261.1062268. ISBN 978-1-59593-019-4.
  3. ^ a b c d Padua, David, ed. (2011). Encyclopedia of Parallel Computing. Boston, MA: Springer US. pp. 453–457, 2033. doi:10.1007/978-0-387-09766-4. ISBN 978-0-387-09765-7.
  4. ^ Mizell, David; Maschhoff, Kristyn (2009). "Early experiences with large-scale Cray XMT systems". 2009 IEEE International Symposium on Parallel & Distributed Processing. pp. 1–9. doi:10.1109/IPDPS.2009.5161108. ISBN 978-1-4244-3751-1. S2CID 1964042.
  5. ^ a b c d Maltby, James (2012). Cray XMT Multithreated programming model. "Using the next-generation Cray XMT (uRiKA) for Large Scale Data Analytics." Swiss National Supercomputing Centre.
  6. ^ Cray XMT™ System Overview (S-2466-201) (PDF). Cray. 2011. Archived (PDF) from the original on December 3, 2012. Retrieved May 12, 2020.
  7. ^ a b Konecny, Petr (2011). Introducing the Cray XMT (PDF). Cray.