A multi-mode hard disk backplane structure, method, and server

Abstract

This invention relates to a multi-mode hard drive backplane structure, method, and server. The application connects to a RAID controller via an uplink connector. Different downlink ports of the RAID controller are connected to the uplink ports of a PCIe switching controller and a SAS expansion controller, respectively. The downlink ports of the PCIe switching controller are connected to each hard drive connector on the backplane via a PCIe bus, and the downlink ports of the SAS expansion controller are connected to each hard drive connector on the backplane via a SAS bus. The PCIe switching controller and the SAS expansion controller are respectively connected to a backplane controller. The backplane controller has pins on the hard drive connectors to identify the hard drive type based on the pin levels. The backplane controller controls the operating state of the PCIe switching controller and the SAS expansion controller connected to the hard drive connectors based on the hard drive type, enabling each hard drive connector to be compatible with SAS, NVMe, and SATA hard drives. This allows the multi-mode hard drive backplane structure to support mixed insertion of different types of hard drives, providing greater adaptability to various hard drives.

Description

Technical Field

[0001] This invention relates to the field of backplane design, and more particularly to a multi-mode hard drive backplane structure, method, and server. Background Technology

[0002] In recent years, with the rapid development of internet technology, the computing power and storage density of servers have experienced explosive growth. Among these components, the hard drive backplane, a crucial part of the server system, serves as a bridge between the motherboard and storage units. It connects upstream to the CPU or RAID card and downstream to various hard drives. The main functions of the backplane include: receiving high-speed input signals; providing power to the hard drives; supporting hard drive alarms; and expanding the number of hard drives.

[0003] Existing backplane designs have the following drawbacks: SAS / NVMe hard drive backplanes supporting RAID have complex wiring. Each uplink interface on the SAS / NVMe hard drive backplane requires a PCIe slot if a RAID card is connected, and PCIe slots are often located on a different layer within the server than the backplane. This leads to complex cabling and cross-wiring between the RAID card and the backplane, affecting heat dissipation and the reliability of high-speed links. The backplane controller on the backplane requires an additional connector interface to connect to the motherboard's baseboard management controller. The patented structure, method, and media for processor-adaptive SATA and NVMe M.2 provide a circuit that adapts M.2 interfaces to NVMe and SATA hard drives. This circuit configures a PCIe-to-SATA bridge and a channel selection unit for each M.2 interface. When applied to backplanes with multiple hard drive connectors, it requires an equal number of PCIe-to-SATA bridges as the number of hard drive connectors, resulting in a more complex overall backplane circuit and higher cost. Summary of the Invention

[0004] To solve the above-mentioned technical problems, or at least partially solve them, the present invention provides a multi-mode hard disk backplane structure, method, and server.

[0005] In a first aspect, the present invention provides a multi-mode hard drive backplane structure, comprising: an uplink connector connected to a central processing unit's PCIe downlink connector via a PCIe bus; the uplink connector being connected via a PCIe bus to an uplink port of a RAID controller supporting multi-mode bus output; one downlink port of the RAID controller being connected via a PCIe bus to an uplink port of a PCIe switching controller, and another downlink port of the RAID controller being connected via a SAS bus to an uplink port of a SAS expansion controller; the downlink port of the PCIe switching controller being connected via a PCIe bus to each hard drive connector on the backplane, and the downlink port of the SAS expansion controller being connected via a SAS bus to each hard drive connector on the backplane; the RAID controller providing RAID management for SATA hard drives, SAS hard drives, or NVMe hard drives connected to the hard drive connectors in the backplane;

[0006] The PCIe switching controller and the SAS expansion controller are respectively connected to the backplane controller. The backplane controller is connected to the hard drive connector and has pins set to identify the hard drive type of each hard drive connector according to the set pin level. The backplane controller controls the working status of the downlink ports of the PCIe switching controller and the SAS expansion controller connected to the hard drive connector based on the hard drive type.

[0007] Furthermore, the backplane controller is connected to the SAS expansion controller via SGPIO, the backplane controller is connected to the PCIe switching controller via I2C bus, the backplane controller is connected to backplane indicator lights, and the backplane controller controls the backplane indicator lights based on the hard drive status information obtained from the SAS expansion controller and the PCIe switching controller.

[0008] Furthermore, the hard drive connector is a SAS / SATA / NVMe multi-mode hard drive connector that supports the SFF8639 protocol.

[0009] Furthermore, the signal lines on the side of the uplink connector are configured with system management bus signal lines. The system management bus signal lines are connected to the baseboard management controller of the server and the backplane controller on the backplane via the system management bus. The backplane controller uploads information, including the type of hard drive connected to the hard drive connector on the backplane and the hard drive status information, to the baseboard management controller via the system management bus.

[0010] Furthermore, the set pins are pins 4 and 10 of the hard drive connector, and the backplane controller is connected to pins 4 and 10 of each hard drive connector on the backplane, and identifies the hard drive type of each hard drive connector based on the voltage levels of pins 4 and 10.

[0011] Furthermore, each hard drive connector on the backplane is connected to two redundant PCIe switching controllers, which are connected to the downlink port of the RAID controller and two redundant SAS expansion controllers. The redundant SAS expansion controllers are connected to the downlink port of the RAID controller. The backplane controller controls the switching of the two redundant PCIe switching controllers and the two redundant SAS expansion controllers.

[0012] Secondly, the present invention provides a multi-mode hard disk backplane control method, applied to the aforementioned multi-mode hard disk backplane structure, comprising:

[0013] After a hard drive is connected to any hard drive connector on the backplane, the backplane controller identifies the set pin level of that hard drive connector and identifies the type of hard drive connected to each hard drive connector based on the set pin level.

[0014] The backplane controller controls the downlink port operation status of the PCIe switching controller and SAS expansion controller connected to the hard drive connector based on the hard drive type:

[0015] When the hard drive connector is connected to an NVMe hard drive, the backplane controller enables the downstream port of the PCIe switching controller connected to the hard drive connector to work, and the backplane controller controls the downstream port of the SAS expansion controller connected to the hard drive connector to be inactive.

[0016] When the hard drive connector is identified as being connected to a SAS hard drive or a SATA hard drive, the backplane controller enables the downlink port of the SAS expansion controller connected to the hard drive connector to work, and the backplane controller disables the downlink port of the PCIe switching controller connected to the hard drive connector.

[0017] The RAID controller supports multi-mode bus output and provides RAID management for SATA, SAS, or NVMe hard drives.

[0018] Furthermore, the backplane controller, based on the hard disk status information obtained from the SAS expansion controller and the PCIe switching controller, controls the backplane indicator lights to issue corresponding indications.

[0019] Furthermore, when each hard drive connector on the backplane is connected to two redundant PCIe switching controllers, and / or when each hard drive connector on the backplane is connected to two redundant SAS expansion controllers, the backplane controller controls the switching of the two redundant PCIe switching controllers according to the status of the PCIe switching controllers, and / or, the backplane controller controls the switching of the two redundant SAS expansion controllers according to the status of the SAS expansion controllers.

[0020] Thirdly, the present invention provides a server configured with at least one of the aforementioned multi-mode hard disk backplane structures.

[0021] The technical solutions provided in the embodiments of the present invention have the following advantages compared with the prior art:

[0022] In this application, the uplink connector is connected to the uplink port of a RAID controller supporting multi-mode bus output via a PCIe bus. One downlink port of the RAID controller is connected to the uplink port of a PCIe switching controller via a PCIe bus, and another downlink port of the RAID controller is connected to the uplink port of a SAS expansion controller via a SAS bus. The downlink port of the PCIe switching controller is connected to each hard drive connector on the backplane via a PCIe bus, and the downlink port of the SAS expansion controller is connected to each hard drive connector on the backplane via a SAS bus. The backplane controller controls the working status of the downlink ports of the PCIe switching controller and the SAS expansion controller connected to the hard drive connectors based on the hard drive type. Each hard drive connector is compatible with SAS, NVMe, and SATA hard drives, enabling the multi-mode hard drive backplane structure to support mixed insertion of different types of hard drives and providing greater adaptability to different hard drives. The RAID controller is configured on the backplane to achieve RAID management of the hard drives connected to the hard drive connectors on the backplane. The multi-mode hard drive backplane structure is connected to the central processing unit and baseboard management controller on the motherboard via the uplink connector, simplifying the wiring between the backplane and the motherboard.

[0023] In this application, each hard drive connector of the multi-mode hard drive backplane structure is connected to two redundant PCIe switching controllers and / or two redundant SAS expansion controllers; the backplane controller controls the switching of the redundant PCIe switching controllers and / or controls the switching of the redundant SAS expansion controllers, thereby enhancing the robustness of the multi-mode hard drive backplane structure. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of a multi-mode hard disk backplane structure provided in an embodiment of the present invention;

[0027] Figure 2A schematic diagram of a SAS expansion controller with multiple SAS expansion chips cascaded according to an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of another multi-mode hard disk backplane structure provided in an embodiment of the present invention;

[0029] Figure 4 A flowchart of a multi-mode hard disk backplane control method provided in an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram of a server with a multi-mode hard drive backplane structure provided for an embodiment of the invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0033] Example 1

[0034] See Figure 1 As shown, the present invention provides a multi-mode hard disk backplane structure, comprising:

[0035] An uplink connector is mounted on the backplane, which is connected to the PCIe connector on the motherboard via a PCIe bus. The PCIe connector on the motherboard is connected to the PCIe downlink connector of the central processing unit via a PCIe bus.

[0036] In a preferred embodiment, the sideband of the uplink connector is configured with a system management bus signal line, which connects to the server's baseboard management controller and the backplane controller on the backplane via the system management bus. After connecting the backplane controller to the baseboard management controller, the backplane controller can send backplane-related information it has acquired to the baseboard management controller, and the baseboard management controller transmits control commands to the backplane controller to control the backplane status. Specifically, the backplane controller uploads information including the type of hard drive connected to the hard drive connector on the backplane and the hard drive status information to the baseboard management controller via the system management bus.

[0037] The uplink connector is connected via a PCIe bus to the uplink port of the RAID controller, which supports multimode bus output and is located on the backplane; one downlink port of the RAID controller is connected via a PCIe bus to the uplink port of the PCIe switching controller, and the other downlink port of the RAID controller is connected via a SAS bus to the uplink port of the SAS expansion controller.

[0038] When the number of hard drive connectors on the backplane exceeds the maximum number of hard drive connectors supported by a single SAS expansion chip, refer to [the relevant documentation]. Figure 2 As shown, in a preferred embodiment, the SAS expansion controller provided in this application consists of a cascade of multiple SAS expansion chips, one of which serves as an output expander. The uplink port of the SAS expansion chip serving as an output expander is connected to the RAID controller, and the downlink port of the SAS expansion chip serving as an output expander is cascaded with SAS expansion chips serving as edge expanders.

[0039] The downstream port of the PCIe switching controller is connected to each hard drive connector on the backplane via the PCIe bus, and the downstream port of the SAS expansion controller is connected to each hard drive connector on the backplane via the SAS bus. In specific implementation, the hard drive connectors used are SAS / SATA / NVMe multi-mode hard drive connectors that support the SFF8639 protocol.

[0040] The RAID controller provides RAID management for SATA, SAS, or NVMe hard drives connected to the hard drive connectors in the backplane.

[0041] The PCIe switching controller and the SAS expansion controller are respectively connected to the backplane controller. Specifically, the PCIe switching controller is connected to the backplane controller via an I2C bus to enable communication between the PCIe switching controller and the backplane controller, and the SAS expansion controller is connected to the backplane controller via an SGPIO bus.

[0042] The backplane controller connects to designated pins on the hard drive connectors to identify the type of hard drive connected to each connector based on the voltage levels of these designated pins. These designated pins are pins 4 and 10 of the hard drive connectors. The backplane controller connects to pins 4 and 10 of each hard drive connector on the backplane and identifies the type of hard drive connected to each connector based on the voltage levels of pins 4 and 10. Pins 4 and 10 can provide a total of four different voltage levels, sufficient to identify whether a hard drive is connected and its type.

[0043] The backplane controller controls the operating status of the downlink ports of the PCIe switching controller and SAS expansion controller connected to the hard drive connector based on the hard drive type. In specific implementation, when the backplane controller identifies any hard drive connector connected to an NVMe hard drive, it enables the downlink port of the PCIe switching controller connected to that hard drive connector to operate, and disables the downlink port of the SAS expansion controller connected to that hard drive connector. When the backplane controller identifies any hard drive connector connected to a SAS hard drive or a SATA hard drive, it enables the downlink port of the SAS expansion controller connected to that hard drive connector to operate, and disables the downlink port of the PCIe switching controller connected to that hard drive connector.

[0044] To intuitively identify the status of the backplane hard drives, a backplane indicator light is configured on the backplane, and the backplane controller is connected to the backplane indicator light. The backplane controller is connected to the SAS expansion controller via SGPIO and to the PCIe switching controller via I2C bus. The backplane controller obtains hard drive status information from the SAS expansion controller and the PCIe switching controller via SGPIO and I2C bus, respectively, and controls the backplane indicator light to provide corresponding indications based on the hard drive status information.

[0045] Example 2

[0046] See Figure 3 As shown, the multi-mode hard drive backplane structure provided in this embodiment of the invention differs from that in Embodiment 1 in that:

[0047] Each hard drive connector on the backplane connects to two redundant PCIe switching controllers. These redundant PCIe switching controllers are connected to the downlink port of the RAID controller. The backplane controller connects to these redundant PCIe switching controllers to enable switching between them: during operation, the backplane controller controls one of the redundant PCIe switching controllers to operate while the other is inactive. When the operating PCIe switching controller fails, the backplane controller switches to the other active PCIe switching controller. Figure 3As shown, PCIe switching controller a and PCIe switching controller b are redundant. For any hard drive connector, a downstream port of PCIe switching controller a and a downstream port of PCIe switching controller b are connected to the PCIe bus connector in that hard drive connector.

[0048] And / or, each hard drive connector on the backplane connects to two redundant SAS expansion controllers. These redundant SAS expansion controllers are connected to the downlink port of the RAID controller. The backplane controller connects to the redundant SAS expansion controllers to achieve switching between them: during operation, the backplane controller controls one of the redundant SAS expansion controllers to operate while the other is not. When the operating SAS expansion controller fails, the backplane controller switches to the other normal SAS expansion controller. Figure 3 As shown, SAS expansion controller a and SAS expansion controller b are redundant. For any hard disk connector, a downstream port of SAS expansion controller a and a downstream port of SAS expansion controller b are connected to the PCIe bus connector in that hard disk connector.

[0049] Example 3

[0050] This invention provides a multi-mode hard disk backplane control method, applied to the aforementioned multi-mode hard disk backplane structure, comprising:

[0051] After a hard drive is connected to any hard drive connector in the multi-mode hard drive backplane structure, the backplane controller identifies the set pin level of that hard drive connector. The set pins are pins 4 and 10 of the hard drive connector.

[0052] The backplane controller identifies the type of hard drive connected to each hard drive connector based on the voltage levels of pins 4 and 10. The voltage levels of pins 4 and 10 include four states: high-high, high-low, low-high, and low-low. One state corresponds to the default state when no hard drive is connected to the connector, while the other three states correspond to different hard drive types.

[0053] The backplane controller controls the downlink port operation status of the PCIe switching controller and SAS expansion controller connected to the hard drive connector based on the hard drive type:

[0054] When the backplane controller recognizes that the hard drive connector is connected to an NVMe hard drive, the backplane controller enables the downstream port of the PCIe switching controller connected to the hard drive connector to work, and the backplane controller controls the downstream port of the SAS expansion controller connected to the hard drive connector to be inactive.

[0055] When the hard drive connector is identified as being connected to a SAS or SATA hard drive, the backplane controller enables the downstream port of the SAS expansion controller connected to the hard drive connector to operate, and the backplane controller disables the downstream port of the PCIe switching controller connected to the hard drive connector.

[0056] The RAID controller in the multi-mode hard drive backplane structure supports multi-mode bus output (PCIe output or SAS output) and provides RAID management for SATA hard drives, SAS hard drives or NVMe hard drives connected to the hard drive connectors in the backplane.

[0057] In practice, the backplane controller uses hard drive status information obtained from the SAS expansion controller and PCIe switching controller to control the backplane indicator lights to issue corresponding indications. Specifically, the backplane controller identifies whether a hard drive connector is connected and the type of hard drive based on the voltage level of each hard drive connector's pin settings. The backplane controller then uploads this information to the baseboard management controller via the management system bus.

[0058] When each hard drive connector on the backplane is connected to two redundant PCIe switching controllers, and / or when each hard drive connector on the backplane is connected to two redundant SAS expansion controllers, the backplane controller controls the switching of the two redundant PCIe switching controllers based on the status of the PCIe switching controllers, and / or, the backplane controller controls the switching of the two redundant SAS expansion controllers based on the status of the SAS expansion controllers. Specifically, during operation, the backplane controller controls one of the redundant PCIe switching controllers to operate while the other is not operating. When the operating PCIe switching controller fails, the backplane controller controls the switching to another normal PCIe switching controller. And / or, the backplane controller controls one of the redundant SAS expansion controllers to operate while the other is not operating. When the operating SAS expansion controller fails, the backplane controller controls the switching to another normal SAS expansion controller.

[0059] Example 4

[0060] See Figure 5 As shown, an embodiment of the present invention provides a server, the server being configured with at least one multi-mode hard disk backplane structure as described in Embodiment 1 or Embodiment 2; the uplink connector on the multi-mode hard disk backplane structure is connected to the PCIe connector on the motherboard via a PCIe bus, the motherboard PCIe connector is connected to the central processing unit's PCIe downlink connector via a PCIe bus, and the central processing unit's PCIe downlink connector is connected to the central processing unit.

[0061] In the embodiments provided by this invention, it should be understood that the disclosed structures and methods can be implemented in other ways. For example, the structural embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interfaces, structures, or units, and may be electrical, mechanical, or other forms.

[0062] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0063] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0064] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A multi-mode hard disk backplane structure, characterized in that, The application relates to a multi-mode hard disk backplane structure. An uplink connector of a central processor PCIe downlink connector is connected through a PCIe bus; The uplink connector is connected to an uplink port of a RAID controller supporting multi-mode bus output through a PCIe bus; At least one downlink port of the RAID controller is connected to an uplink port of a PCIe switch controller through a PCIe bus, and at least one downlink port of the RAID controller is connected to an uplink port of a SAS expansion controller through a SAS bus; Downlink ports of the PCIe switch controller are connected to each hard disk connector on a backplane through a PCIe bus, and downlink ports of the SAS expansion controller are connected to each hard disk connector on the backplane through a SAS bus; the RAID controller in the multi-mode hard disk backplane structure supports multi-mode bus output, and provides RAID management for SATA hard disks, SAS hard disks or NVMe hard disks connected to the hard disk connectors on the backplane; The PCIe switch controller and the SAS expansion controller are connected to a backplane controller respectively, the backplane controller is connected to a setting pin on the hard disk connector to identify the hard disk type of the hard disk connected to each hard disk connector according to the setting pin level, and the backplane controller controls the working state of the downlink ports of the PCIe switch controller and the SAS expansion controller connected to the hard disk connector based on the hard disk type; After any hard disk connector in the multi-mode hard disk backplane structure is connected to a hard disk, the backplane controller identifies the setting pin level of the hard disk connector; the hard disk type of the hard disk connected to each hard disk connector is identified according to the setting pin level; the working state of the downlink ports of the PCIe switch controller and the SAS expansion controller connected to the hard disk connector is controlled by the backplane controller based on the hard disk type: when the hard disk connector is connected to an NVMe hard disk, the backplane controller enables the downlink port of the PCIe switch controller connected to the hard disk connector to work, and the backplane controller controls the downlink port of the SAS expansion controller connected to the hard disk connector to not work; when the hard disk connector is connected to a SAS hard disk or a SATA hard disk, the backplane controller enables the downlink port of the SAS expansion controller connected to the hard disk connector to work, and the backplane controller controls the downlink port of the PCIe switch controller connected to the hard disk connector to not work; the RAID controller supports multi-mode bus output, and provides RAID management for SATA hard disks, SAS hard disks or NVMe hard disks.

2. The multi-mode hard disk backplane structure of claim 1, wherein, The backplane controller is connected to the SAS expansion controller through an SGPIO, connected to the PCIe switch controller through an I2C bus, connected to a backplane indicator, and controls the backplane indicator according to the hard disk state information obtained from the SAS expansion controller and the PCIe switch controller; the backplane controller controls the backplane indicator to issue corresponding indications according to the hard disk state information.

3. The multi-mode hard disk backplane structure of claim 1, wherein, The hard disk connector is a SAS / SATA / NVMe multi-mode hard disk connector supporting an SFF8639 protocol.

4. The multi-mode hard disk backplane structure of claim 1, wherein, The signal line of the uplink connector sideband is configured as a system management bus signal line, which is connected to a baseboard management controller of the server and a backboard controller on the backboard via a system management bus, and the backboard controller transmits information including the type of hard disk connected to the hard disk connector on the backboard and the state information of the hard disk to the baseboard management controller via the system management bus.

5. The multi-mode hard disk backplane structure of claim 1, wherein, The setting pins are the No. 4 pin and the No. 10 pin of the hard disk connector, the backboard controller connects the No. 4 pin and the No. 10 pin of each hard disk connector on the backboard, and the type of hard disk connected to each hard disk connector is identified according to the level of the No. 4 pin and the No. 10 pin.

6. The multi-mode hard disk backplane structure of claim 1, wherein, Each hard disk connector on the backboard is connected to two mutually redundant PCIe switching controllers, the mutually redundant PCIe switching controllers are connected to the downstream ports of the RAID controller, two mutually redundant SAS expansion controllers are connected, the mutually redundant SAS expansion controllers are connected to the downstream ports of the RAID controller, the backboard controller controls the switching of the two mutually redundant PCIe switching controllers, and the backboard controller controls the switching of the two mutually redundant SAS expansion controllers; when each hard disk connector on the backboard is connected to two mutually redundant PCIe switching controllers and / or each hard disk connector on the backboard is connected to two mutually redundant SAS expansion controllers, the backboard controller controls the switching of the two mutually redundant PCIe switching controllers according to the status of the PCIe switching controllers, and / or the backboard controller controls the switching of the two mutually redundant SAS expansion controllers according to the status of the SAS expansion controllers.

7. A server, characterized by The server is configured with at least one multi-mode hard disk backboard structure as claimed in any one of claims 1-6.

Images