[PATCH] documentation for voyager

Documentation/voyager.txt

+Running Linux on the Voyager Architecture
+=========================================
+
+For full details and current project status, see
+
+http://www.hansenpartnership.com/voyager
+
+The voyager architecture was designed by NCR in the mid 80s to be a
+fully SMP capable RAS computing architecture built around intel's 486
+chip set.  The voyager came in three levels of architectural
+sophistication: 3,4 and 5 --- 1 and 2 never made it out of prototype.
+The linux patches support only the Level 5 voyager architecture (any
+machine class 3435 and above).
+
+The Voyager Architecture
+------------------------
+
+Voyager machines consist of a Baseboard with a 386 diagnostic
+processor, a Power Supply Interface (PSI) a Primary and possibly
+Secondary Microchannel bus and between 2 and 20 voyager slots.  The
+voyager slots can be populated with memory and cpu cards (up to 4GB
+memory and from 1 486 to 32 Pentium Pro processors).  Internally, the
+voyager has a dual arbitrated system bus and a configuration and test
+bus (CAT).  The voyager bus speed is 40MHz.  Therefore (since all
+voyager cards are dual ported for each system bus) the maximum
+transfer rate is 320Mb/s but only if you have your slot configuration
+tuned (only memory cards can communicate with both busses at once, CPU
+cards utilise them one at a time).
+
+Voyager SMP
+-----------
+
+Since voyager was the first intel based SMP system, it is slightly
+more primitive than the Intel IO-APIC approach to SMP.  Voyager allows
+arbitrary interrupt routing (including processor affinity routing) of
+all 16 PC type interrupts.  However it does this by using a modified
+5259 master/slave chip set instead of an APIC bus.  Additionally,
+voyager supports Cross Processor Interrupts (CPI) equivalent to the
+APIC IPIs.  There are two routed voyager interrupt lines provided to
+each slot.
+
+Processor Cards
+---------------
+
+These come in single, dyadic and quad configurations (the quads are
+problematic--see later).  The maximum configuration is 8 quad cards
+for 32 way SMP.
+
+Quad Processors
+---------------
+
+Because voyager only supplies two interrupt lines to each Processor
+card, the Quad processors have to be configured (and Bootstrapped) in
+as a pair of Master/Slave processors.
+
+In fact, most Quad cards only accept one VIC interrupt line, so they
+have one interrupt handling processor (called the VIC extended
+processor) and three non-interrupt handling processors.
+
+Current Status
+--------------
+
+The System will boot on Mono, Dyad and Quad cards.  There was
+originally a Quad boot problem which has been fixed by proper gdt
+alignment in the initial boot loader.  If you still cannot get your
+voyager system to boot, email me at:
+
+<J.E.J.Bottomley@HansenPartnership.com>
+
+
+The Quad cards now support using the separate Quad CPI vectors instead
+of going through the VIC mailbox system.
+
+The Level 4 architecture (3430 and 3360 Machines) should also work
+fine.
+
+Dump Switch
+-----------
+
+The voyager dump switch sends out a broadcast NMI which the voyager
+code intercepts and does a task dump.
+
+Power Switch
+------------
+
+The front panel power switch is intercepted by the kernel and should
+cause a system shutdown and power off.
+
+A Note About Mixed CPU Systems
+------------------------------
+
+Linux isn't designed to handle mixed CPU systems very well.  In order
+to get everything going you *must* make sure that your lowest
+capability CPU is used for booting.  Also, mixing CPU classes
+(e.g. 486 and 586) is really not going to work very well at all.