| <- HREF="node37.html" Prev | Index | Next -> |
NHSE ReviewTM: Comments
· Archive
· Search
| Machine type | Distributed-memory multi-processor |
|---|---|
| Models | nCUBE 3 |
| Operating system | Internal OS transparent to the user, SunOS (Sun's Unix variant) on the front-end system |
| Connection structure | Hypercube |
| Compilers | Extended Fortran 77, ANSI C, C++ |
System parameters:
| Model | nCUBE 3 |
|---|---|
| Clock cycle | 10 ns |
| Theor. peak performance | |
| Per Proc. (64-bits) | 100 Mflop/s |
| Maximal(64-bits) | 1024 Gflop/s |
| Main memory | <=1 |
| Memory/node | <=1 |
| Communication bandwidth | |
| Point-to-point | 115 MB/s |
| No. of processors | 8-10244 |
Remarks:
The nCUBE 3 is presently the only commercially available machine
with a hypercube structure. The nCUBE uses in-house developed processors
implemented in 0.5
m CMOS which have a performance of 100 Mflop/s in 64-bit
precision (in contrast to the former 2S model, the new processor is entirely
64-bit wide). The node processor has 8 KB instruction and data caches, both
2-way set associative. Furthermore, each processor has miss and write buffers
of
four operands deep that allows for 4 cache misses (or deferring four cache
writes) before disturbing the data cache.
There are 16 outward DMA channels per node (8 send and 8 receive) for
inter-processor communication while an additional one is used for the
distributed I/O system which therefore has the nice property that it scales
with the number of nodes. The speed of these I/O nodes is 20 MB/s full-duplex.
The communication latency is quite low: about 3
s
while the single channel
bandwidth is 50 MB/s. By ``folding'' multiple channels higher point-to-point
bandwidth can be achieved. For the instruction cache an autoprefetch facility
is implemented while prefetch for the data cache is compiler directed. On 1024
processors with 6 ports folded a bisectional bandwidth of 45.5 GB/s can be
realised.
Apart from the fixed wormhole routing scheme that already was employed in the former nCUBE systems, a new fault-tolerant adaptive routing scheme is available. This scheme is also essentially a wormhole routing but with the additional constraint that after the first hop the distance to the target node should strictly decrease. Therefore, no cycles can occur and delivering of a message is guaranteed to be done in a finite number of hops.
Within the hypercube sub-cubes can be allocated to accommodate more users. A queue of tasks is set up with (sub)-cubes of the required size. Programs may be written to determine the sub-cube dimensions just before execution.
Measured Performances: The first system is expected to be realised in the 2nd quarter of 1995, so no real performance figures are available. Simulations showed a single node speed of 96 Mflop/s on a matrix-matrix multiply and of 40 Mflop/s on a matrix-vector multiply.
Copyright © 1996 Aad J. van der Steen and Jack J. Dongarra
| <- HREF="node37.html" Prev | Index | Next -> |
NHSE ReviewTM: Comments
· Archive
· Search
NHSE: Software Catalog
· Roadmap