
Chapter 3. The Cray T3E system 27
3.7 External I/O
The T3E system has four processing elements per one I/O controller,
while one out of every two I/O controllers is connected to a GigaRing
controller. These controllers can be connected to external I/O clients
through high-speed GigaRing channels. Figure 3.5 illustrates the I/O
path from a PE to an external disk device.
Micro-
processor
Local
Memory
Support
Circuitry
Network
Router
-Z +Z
+Y
-Y-X
+X
I Chip
GigaRing
Chip
GigaRing
Client
Processing Element
I/O Controller
Interconnection
Network
Disk
Drives
Figure 3.5: A Cray T3E node with external I/O.
The GigaRing architecture is implemented using a dual-ring design, with
data in the two rings traveling in opposite directions. The raw data
bandwidth of one ring is up to 600 MB/s which gives a total of 1200 MB/s
per channel. The peak data bandwidth is 800 MB/s per channel for
half-duplex connections and 2 × 700MB/s for full-duplex connections
between two GigaRing nodes. The data bandwidth from a T3E node
is limited by the connection through the Network Router and the I/O
controller. Thus, the bandwidth is up to 500 MB/s.
GigaRing channels can be configured with multiple nodes of different
type, a Multi Purpose Node (MPN) or a Single Purpose Node (SPN). In an
MPN several types of I/O controllers can be installed: FDDI, Ethernet,
ATM or SCSI.
Kommentare zu diesen Handbüchern