[rescue] J90 on epay

[Michael Thompson]

>>    Each IOS VME64 chassis' backplane is broken into four segments and 
>> can hold four separate IOS board sets...each with its own SS5, IOBB, 
>> and disk/network interfaces.  An IOBB interface connects via a big fat 
>> cable to a mezzanine card mounted in one of the J90 CPU modules.  Each 
>> CPU module has four mezzanine slots which can hold either an IOBB 
>> interface, a HIPPI source board, or a HIPPI destination board.  With 
>> four mezzanine slots on each CPU module, and a maximum of four CPU 
>> modules in a J916, that means up to sixteen IOSs.  Most have one or two 
>> at most.  A minimally-configured J90 consists of two cabinets, and a 
>> big one can be up to five.

With apologies to the Cray Master Dave, let me try to explain booting in
Sun terms instead of Cray terms.

The IOP in the VME64 backplane is a SPARC architecture VME64 board
manufactured by Themis. In Sun terms it is not a SS5, but it's architecture
is nearly identical. It has an S-bus to VMEbus bridge chip on the board
that allows it to talk across the VME64 backplane. The IOP doesn't run
Solaris or SunOS, it runs CRAY IOS-V software based on the VXworks real
time kernel. It just does I/O.

The OWS (a real SS5 workstation) is the operator's console and boot server
for the VME64 SPARC IOP boards. It runs Solaris and a Cray GUI program. It
is connected to the IOS with a thin-wire Ethernet.

To boot the J90 the VME64 SPARC board does a reverse ARP, gets an IP
address from the SS5, loads VXworks over the Ethernet from the SS5 using
BOOTP, and then uses the SS5 as the console for the IOS-V real time kernel
running on the IOS.

Once the IOP is booted and talking to the OWS you can log into the IOS-V
software running on the IOP. You can then tell the IOP to read UNICOS from
SCSI disks connected to the VME SCSI controller and load it into the CRAY's
memory through the I/O Buffer Board. The IOP then lights off the CRAY CPUs
and UNICOS comes up. UNICOS does networking through VME ATM and Ethernet
boards. You can switch the OWS connection between UNICOS and IOS-V.

After UNICOS is up the SS5 is just a console. This caused a lot of
complaints among CRAY owners.

>I had no idea that HIPPI would be installed as something other than
>VME64.  Is this for latency reasons, or is VME64 not as fast as I would
>have expected?  For some reason, I expected that VME64 would be faster
>than PCI/X.

VME64 has a theoretical maximum throughput of about 80MB/s. The latest
version of VME64x with Source Synchronous Block Transfers can top out over
320MB/s. VME64x supports 21 backplane slots which makes it popular for
Industrial and I/O applications. PCI/X has a theoretical maximum throughput
of about 1GB/s. It has not been adopted as part of CompactPCI yet so it is
not available in industrial strength systems.
 
>>    The EL family boots in the same way, except the IOS (which is a VME 
>> 68020 CPU board) boots from a locally-attached SCSI disk instead of 
>> over the ethernet from the OWS.  It uses a regular ASCII console 
>> terminal connected to the "master" (if there's more than one) IOS's 68K 
>> CPU board.

The 68020 IOP was made by Heurikon?


Michael Thompson
E-Mail: M_Thompson at IDS.net