Ht systems, Ht systems –2, Figure 3–2. ht systems – Altera HyperTransport MegaCore Function User Manual
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Chapter 3: Specifications
HyperTransport Technology Overview
HyperTransport MegaCore Function User Guide
© November 2009
Altera Corporation
Preliminary
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End-Chain Link—The end-chain link device is the simplest of all HT devices and
only one can exist in an HT chain. This single-link device claims packets when the
destination address of the packet matches its address. If it receives a packet that
does not match its address, it must indicate an error condition by setting
appropriate error bits or sending a return packet indicating that an error occurred.
The Altera
HyperTransport MegaCore function implements an end-chain link.
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Tunnel—A tunnel is a dual-link device that is not a
HyperTransport-to-HyperTransport bridge. In the upstream direction, tunnels
transfer all packets except for information packets directly from the downstream
link to the upstream link. In the downstream direction, only packets that are not
claimed by the device are transferred to the downstream interface.
■
HyperTransport-to-HyperTransport Bridge—This bridge has one or more HT links
and is more complex than a tunnel because it translates packets from one chain to
two or more chains. The bridge must take upstream traffic from secondary chains
and forward the packets to the primary chain while maintaining I/O streams,
virtual channel ordering, and error conditions.
HT Systems
HT systems, or fabrics, are implemented as one or more daisy chains of HT devices.
shows two of the three variations of HT fabric configurations. You can use
the HyperTransport MegaCore function as the end-chain link in any of these systems.
Figure 3–2. HT Systems
Host Bridge
(Master)
HT Link
Interface
Mem
T
unnel
Tunnel
HT Link
Interface
Tree
CPU
T
unnel
HT-to-HT Bridge
HT Link
(P)
HT Link
(S)
End-Chain
HT Link
Interface
End-Chain
HT Link
Interface
Primary
Chain
Secondary
Chain
Host Bridge
HT Link
Interface
T
unnel
Tunnel
HT Link
Interface
T
unnel
Tunnel
HT Link
Interface
End-Chain
HT Link
Interface
Chain
Mem
CPU