Information about the Albireo computer system
The Albireo computer consists of two Sun Ultra Enterprise 6000 servers.
Each server
has:
- 16 UltraSparcII processors (250 MHz). Each processor has a 4 Mbyte
L2 cache.
- 4 Gbyte of primary storage.
- A 2.7 Gbyte/s shared memory bus.
The two servers are interconnected using the Sun WildFire interconnect,
which in effect creates a single shared memory of 8 Gbyte from the
memories in the two servers. Albireo is currently the only installation of
the WildFire interconnect outside the U.S.
For a schematic sketch of the computer set-up, click here.
The total floating point performance for Albireo is 16 Gflop/s. The upgraded
system in the second phase will have a performance of up to 76 Gflop/s.
WildFire's Scalable Shared Memory (SSM)
Each Sun Ultra Enterprise server architecture is the Symmetric
Multiprocessor (SMP). The WildFire system begins with the cabling together
these servers. The interconnect boards link and unify the independent Ultra
Enterprise servers so they become cooperating nodes in a single (not
clustered) new system. Many of the properties of WildFire's SSM architecture
are similar to SMP. But, WildFire's gains over the SMP architecture in
scalability and the processing power comes from its ability to operate as
a distributed shared-memory system in both Cache-Coherent Non-Uniform
Memory Architecture(CC-NUMA) and Cache-Only Memory Architecture
(COMA) switching appropriately from one mode to another during runtime.
SSM architecture supports two different methods for accessing remote memory:
- Direct reference: Per-cache line-sharing state is maintained
within the directory, and local state bits are kept in memory tags. If a
processor requests data from a location that is not in its own cache,
the system generates a remote transaction to retrieve data from either
memory or the appropriate cache, always traversing the directory agent
in the process. Meanwhile, the WildFire Network Interface board keeps track
of the sharing state of each local memory location that is remotely
accessed.
- Coherent Memory Replication (CMR): The WildFire system also
uses some of the local memory to replicate and store remote memory. CMR
uses hardware protocols and local memory as its "third-level cache" for
remote memory. Sharing state is maintained per cache-line and the WildFire
Network Interface Board maintains information about the state of each
memory location that is used to cache remote data. The CMR mode reduces
the number of remote transactions required when applications show some
degree of node locality. Latency is thus reduced as a result of enabling
more local transactions
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HPC utvecklingskonto
Last modified: Thu Nov 25 13:06:18 MET 1999
