Clock distribution in multi-cell computing systems
View Patent ↗Embodiments of the invention relate to distribution of clocks to CPUs in processing cells of a multi-cell system. In an embodiment, each cell includes an interface, referred to as an agent. A plurality of interfaces, referred to as switches, together with the agents of the cells, connects the cells together. A clock source provides a clock to a switch, which replicates the clock and provides the replicated clocks to its ports. Each port of the switch, receiving a replicated clock, encodes this replicated clock and sends it over a link to each agent of a cell. Each agent of the cells, receiving an encoded clock, decodes this encoded clock, resulting in a decoded, or an extracted, clock. The agent then replicates the extracted clock and provides the replicates of the extracted clock to a plurality of CPUs of the cell. As a result, CPUs in all cells of the system receive clocks that all are synchronized to the clock provided by the clock source. Other embodiments are also disclosed including using the extracted clock as phase information, scaling, redundancy, etc.
1. A system comprising:
a plurality of processing cells each having a plurality of processors; and
each processing cell receiving an extracted clock for use in at least one of the following ways
a) the extracted clock being replicated to provide a plurality of first clocks each being fed to a processor of the processing cell;
b) the extracted clock being used as phase information in conjunction with a first clock source to provide a plurality of second clocks each being fed to a processor of the processing cell;
wherein the extracted clock was extracted from an encoded clock being combined with data and sent to the processing cell over a link that allows at least two processing cells to communicate with one another via a switch;
wherein the link is associated with a failed-over link, the encoded clock is associated with a failed-over encoded clock, the extracted clock is associated with a failed-over extracted clock, the first clock source is associated with a failed-over first clock source.
2. The system of claim 1 wherein the encoded clock was encoded using an 8B10B algorithm.
3. The system of claim 1 wherein the plurality of first clocks runs at a first frequency resulted from a second frequency used by the link and the second frequency is resulted from a third frequency run by a clock provided by a second clock source.
4. The system of claim 1 wherein the plurality of second clocks runs at a first frequency resulted from a second frequency used by the link and the second frequency is resulted from a third frequency run by a clock provided by a second clock source.
5. A system comprising:
means for providing a plurality of clocks being encoded and combined with data over a plurality of links; and
a plurality of processing cells each having an agent; each agent of a processing
cell extracting a clock, replicating the extracted clock to provide a plurality of replicated clocks to a plurality of processors of the processing cells; wherein the plurality of replicated clocks in at least two processing cells are being synchronized with a clock provided by a clock source providing the plurality of clocks being encoded and combined with data over the plurality of links; wherein the replicated clocks run at a first frequency scaled down from a second frequency run by the plurality of encoded and combined clocks and the second frequency is scaled up from a third clock frequency run by the clock source.
6. The system of claim 5 wherein at least one of the following is done:
the clock source being associated with a failed-over clock source;
a link of the plurality of links being associated with a failed-over link; and
the extracted clock being associated with a failed-over extracted clock.
7. A system comprising:
means for providing a plurality of clocks being encoded and combined with data over a plurality of links; and
a plurality of processing cells each having an agent; each agent of a processing cell extracting an encoded and combined clock, using the extracted clock as phase in formation in conjunction with a first clock source to provide a plurality of first clocks to a plurality of processors of the processing cell; wherein the plurality of first clocks in at least two processing cells are synchronized with a clock provided by a second clock source providing the plurality of clocks being encoded and combined with data over the plurality of links;
wherein at least one of the following is done
the first clock source being associated with a failed-over first clock source,
the second clock source being associated with a failed-over second clock source,
a link of the plurality of links being associated with a failed-over link,
the extracted clock being associated with a failed-over extracted clock.
8. The system of claim 7 wherein the first clocks run at a first frequency scaled down from a second frequency run by the plurality of encoded and combined clocks and the second frequency is scaled up from a third clock frequency run by the second clock source.
9. A system comprising:
a first clock source providing a first clock;
a switch receiving the first clock and replicating the first clock to provide a plurality of second clocks to a plurality of ports of the switch; a port encoding a second clock to provide an encoded third clock to a link, resulting in a plurality of encoded third clocks on a plurality of links;
a plurality of agents each receiving an encoded third clock from a link of the plurality of links, decoding this encoded third clock to provide an extracted clock; thereby resulting in a plurality of extracted clocks each corresponding to an agent; and
a plurality of processing cells each including an agent of the plurality of agents; thereby resulting in each processing cell of the plurality of processing cells corresponding to an extracted clock of the plurality of extracted clocks;
wherein an extracted clock corresponding to a processing cell is used in at least one of the following ways:
a) the extracted clock being replicated to provide a plurality of fourth clocks each being fed to a processor of the processing cell;
b) the extracted clock being used as phase information in conjunction with a second clock source to provide a plurality of fifth clocks being fed to a processor of the processing cell.
10. The system of claim 9 wherein at least one of the following is associated with a failed-over: the first clock, a second clock, an encoded third clock, an extracted clock, a link, a fourth clock, and a fifth clock.
11. The system of claim 9 wherein a fourth clock of the plurality of fourth clocks runs at a first frequency calculated from a second frequency of the first clock via at least one of a scale up and a scale down technique.
12. The system of claim 9 wherein a fifth clock of the plurality of fifth clocks run at a first frequency calculated from a second frequency of the first clock via at least one of a scale up and a scale down technique.