Dual Processor and SCO MPX

Hardware Details

1. The Dual Processor card contains two switches. Switch 1 controls the processor caching and switch two the RAM address of the card. Switch two should work in either position, Switch 1 should be switched to on or the second CPU will thrash when the system is running.
   
2. When upgrading a single to a dual processor it may be necessary to change the PALs in IC25 and IC26 on the main CPU board. These PALs should be revision VB or later, if they are VA PALs then the PALs supplied with the upgrade kit should be installed.

Software Details

1. SCO MPX for the Apricot DSPA is only available from Apricot and should ideally only be installed on SCO UNIX V/386 3.2 V2.
   
2. All drivers and kernel changes installed after SCO MPX will be lost if SCO MPX is de-installed from the system.
   
3. A new lockd daemon is required for SCO MPX and SCO NFS to co-exist. Please ensure this is installed as /etc/lockd before taking an MPX system into multi-user mode. This lockd daemon is SCO Supplement LNG287 which can be downloaded or emailed from Apricot.
   
4. When installing MPX on an existing machine with SCO TCP/IP, errors may occur referring to sio_tty being undefined in /etc/conf/pack.d/crllry/Driver.o. This is caused by SCO MPX expecting to see the sio driver in the kernel. The sio driver can be removed by running both configure lines for SCO TCP/IP as documented in IPB 3103, to correct this error ensure the line in /etc/conf/sdevice.d/sio reads:

   sio   Y   1   7   0   0   0   0   0  0

   This ensures the driver is present but does not have any interrupts assigned. It is also important that the motherboard serial port is disabled on the reference disk with multiple WD Cards.

5. To examine the CPU usage, the utility mpstat is provided. This utility can be locked on the second CPU if this is required for benchmarking.
   
6. It is recommended that a complete copy of the files below /etc/conf is taken (on tape if necessary) before SCO MPX is installed. This will allow comparison of files like stune which contain details of modifications to the default Unix configuration.
   
7. SCO MPX will not automatically give you a faster machine, the CPU's are still 25 MHz so on the FTe 486 DX-33 a single CPU intensive task can be performed in a faster time. However the benefit is that two CPU's remove the bottleneck created with a single processing unit. Having one CPU performing a CPU intensive task will leave the other one free to service user tasks with no increase in response time. The machine is therefore best suited to high user installations using serial and/or Ethernet connections.

Please note that this IPB supersedes the MPX1 Intermediate Product Bulletin sent by E-mail to approved Multi Processor Centres.

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