Expansion bus devices comprising retimer switches

1. An apparatus, comprising:

an expansion bus device, comprising:

a plurality of input-output slots; and

a retimer switch communicatively connected to each of the plurality of input-output slots to support switching between the plurality of input-output slots, the retimer switch comprising a switch combined with a retimer, and the retimer switch to perform switching of signals between the plurality of input-output slots, and the retimer switch to retime the signals between the plurality of input-output slots; and

a plurality of input-output devices communicatively coupled to the expansion bus device via the plurality of input-output slots.

2. The apparatus of claim 1 , wherein the plurality of input/output devices is arranged into a plurality of subsets, and wherein each subset of the plurality of subsets is communicatively coupled to a respective switch of a plurality of switches.

3. The apparatus of claim 1 , wherein the plurality of input/output devices comprises a plurality of graphics processing units.

4. The apparatus of claim 1 , wherein the plurality of input/output devices comprises a plurality of programmable logic devices.

5. The apparatus of claim 1 , wherein each input-output slot of the plurality of input-output slots comprises a plurality of input-output slot ports.

6. The apparatus of claim 1 , wherein the expansion bus device is configurable to support communications between the plurality of input-output slots at a plurality of levels of granularity.

7. The apparatus of claim 5 , wherein each of the plurality of input-output slot ports comprises a plurality of communication paths, wherein the retimer switch supports switching between communication paths of the plurality of communication paths of the plurality of input-output slot ports to interchangeably connect the plurality of input-output devices.

8. The apparatus of claim 7 , wherein the plurality of communication paths comprises a plurality of high-speed point-to-point connections.

9. The apparatus of claim 6 , wherein the plurality of levels of granularity comprise a first level of granularity at which the expansion bus device supports communications on a per-port basis, and a second level of granularity at which the expansion bus device supports communications on a per-communication path basis.

10. The apparatus of claim 9 , wherein when the expansion bus device is configured at the second level of granularity, the expansion bus device supports communications on Peripheral Component Interconnect (PCI) Express lanes between the plurality of input-output slots.

11. The apparatus of claim 6 , further comprising:

a controller to selectively configure the expansion bus device to a selected level of granularity of the plurality of levels of granularity.

12. A system, comprising:

a first expansion bus device, comprising:

a first plurality of host interface devices to support a plurality of host devices;

a first plurality of input-output slots to support a plurality of input-output devices; and

a first retimer switch communicatively connected to each of the first plurality of host interface devices and to each of the first plurality of input-output slots to support switching between the first plurality of host interface devices and the first plurality of input-output slots, and to retime signals between the first plurality of host interface devices and the first plurality of input-output slots; and

a second expansion bus device, comprising:

a second plurality of input-output slots to support the plurality of input-output devices; and

a second retimer switch communicatively connected to each of the second plurality of input-output slots to support switching of signals between the second plurality of input-output slots, and to retime the signals between the second plurality of input-output slots; and

the plurality of input-output devices communicatively coupled to the first expansion bus device via the first plurality of input-output slots and to the second expansion bus device via the second plurality of input-output slots.

13. The system of claim 12 , wherein the plurality of input/output devices is arranged into a plurality of subsets, and wherein each subset of the plurality of subsets is communicatively coupled to a respective switch of a plurality of switches.

14. The system of claim 12 , wherein the plurality of input/output devices comprises a plurality of graphics processing units.

15. The system of claim 12 , wherein the plurality of input/output devices comprises a plurality of programmable logic devices.

16. The system of claim 13 , wherein each switch of the plurality of switches communicatively couples a subset of the plurality of subsets to an input-output slot of the first plurality of input-output slots.

17. The system of claim 13 , wherein each switch of the plurality of switches comprises a port multiplier.

18. A method, comprising:

receiving a control signal at a retimer switch of an expansion bus device, the expansion bus device comprising a plurality of input-output slots communicatively connected via the retimer switch;

modifying at least one connection connecting at least two of the plurality of input-output slots, in response to the control signal; and

after modifying the at least one connection, switching, by the retimer switch, signals between the plurality of input-output slots, and retiming, by the retimer switch, the signals between the plurality of input-output slots.

19. The method of claim 18 , wherein the modifying alters a configuration of a plurality of input-output devices coupled to the expansion bus device via the plurality of input-output slots.

20. The method of claim 18 , wherein the retimer switch comprises a switch combined with a retimer.