NonStop S-Series Server Description Manual (G06.27+)

Introduction

HP NonStop S-Series Server Description Manual—520331-004

1-16

Expansion to Second Processor Enclosure

Most NonStop systems require that several processor enclosures be connected

together. Such interconnections are provided through specialized, plug-in boards in

processor enclosures that expand the ServerNet fabric from one enclosure to another.

These boards, if present, are installed in pairs in slots 51 through 54 of a processor

enclosures. See Figure 1-3 on page 1-7.

There are two kinds of such boards. The original and simpler version is called a

ServerNet expansion board (SEB), which uses six-port routers. The later version is

called a modular ServerNet expansion board (MSEB). The MSEB uses 12-port routers

(though only seven ports are currently assigned) and is called modular because it

accepts a variety of plug-in cards (PICs), or modules, that permit easy adaptability to

different interconnection protocols. As mentioned previously, in this manual and in

other ServerNet documentation, SEB is often used as a generic term to denote the

basic function.

Figure 1-9 shows how a pair of SEBs can be used to connect one processor enclosure

to another.

The main logic component of a SEB is a router that is additional to the one already

present on the MFIOB. SEBs are always added in pairs because one is needed for the

X fabric and one is needed for the Y fabric.

In each case, the router connection from the MFIOB that connects to an SEB is the

router port that was shown unused in Figure 1-7 and Figure 1-8. The four downward-

pointing arrows from the MFIOB routers connect to the SCSI bus and I/O slots like the

example shown in Figure 1-8 on page 1-15.

The required cables for interconnecting the two processor enclosures are shown with

bold lines in the example in Figure 1-9

. One cable interconnects the X routers on one

SEB in each of the processor enclosures, and the other cable interconnects the Y

routers.

Note that four unused router ports are available on each of the SEBs. These ports can

be used for expanding either, or both, the number of processor enclosures and the

number of I/O enclosures. Expansions of both kinds are the subject of the remaining

topics in this section.

Note. For clarity, the I/O details are omitted in Figure 1-9. As explained in the preceding topic

(Maximum Processor Enclosure I/O), I/O configuration details vary. For example, MFIOB

boards use six-port routers and therefore have three, rather than four, router ports for internal

I/O logic.