Under the Covers

What's inside a Cray J90? I'm going to take a pause in the restoration to "pop the hood" and describe what's under the covers. Here we have the two cabinets bolted together with the doors and most of the panels removed. On the right is the Processing Cabinet and on the left is the Peripheral Cabinet.

The Cray J916 with the front doors and many of the filler panels removed.

The Processing Cabinet has a Central Control Unit at the top which has LEDs that display status and fault conditions. Below that is a plenum space for the cooling blower intake and dust filters. Next is the backplane (the Processor and Memory Modules are inserted from the back.) Under that is the blower which exhausts out the back. At the bottom are the 48 volt DC power supplies.

The Peripheral Cabinet is moderately configured with plenty of space for expansion. In the center is the I/O Subsystem VME Chassis which contains two VME backplanes. Each contains a SPARC single-board computer which functions as an I/O Processor (IOP.) The remaining VME slots contain the system interfaces including Ethernet, disk controllers, and the I/O Buffer Boards (IOBB) that transfer data from peripherals to the J90 processors and memory. At the bottom are two disk arrays.

The VME Chassis.

From left to right the two VME backplanes contain:

1. IOP0 - the Master I/O Processor
2. IOBB-64 - which is cabled to the J90 processor via the first Y1 Channel
3. EI-1 - the system Ethernet
4. DC-6S - dual SCSI disk controller
5. empty
6. empty 

1. IOP1 - a Slave I/O Processor
2. IOBB-64 - which is cabled to the J90 processor via the second Y1 Channel
3. DC-5I - dual IPI disk controller
4. empty

There is room to add a couple more IOPs on the right. Each IOP has a private Ethernet interface. These are 10base5 using AUI connectors. There is an Ethernet hub that connects both of them to the private IOS subnet which is a 10base2 ThinWire cable that also connects to the Service Worksation or SWS for short. The SWS is a Sun workstation that is not pictured. I'll describe that in detail in a later post. The IOS subnet is only used to boot the IOPs and manage the system. The E1-1 is also 10base5 and is used as the main J90 system network interface. We found a VME FDDI board that should be compatible. That upgrade will give the system 100 mbs networking.

The disk arrays, partially opened.

The bottom PE-30S disk array contains four differential fast/wide SCSI ST410800WD drives. They are 9GB each and configured with only two drives on each of the two SCSI buses to maximize performance.

The PE-10I disk array contains four Intelligent Peripheral Interface ST43200K drives. These are 3.GB each with, again, only two drives on each of the two buses. They have a higher throughput than the SCSI drives.