Thanks to David Gatwood, here's some information on the use of mach_options
in lilo.conf.

Comments are in brackets. DG = David Gatwood. SK = Steve Knouse

SK: I've read a number of mentions of using mach_options=-mxxx where
xxx is 96 or 256 or whatever, and of mach_options=-a in lilo.conf.
What does these do? What other options are there? Where are they
documented?

DG: Besides in the source code, they're probably not documented very
well. Here are the ones that I know of:

A. Switches
    -a       - Ask for additional info
    -c       - * Collocate linux server (???)
    -e       - Expansion bay support (PB1400, deprecated)
    -s       - Single user
    -v       - Cached console Video (deprecated)
    -mXXX  - XXX = the amount of memory in MB Linux will use

* - this is really a linux server option that can be passed from
    lilo.conf, I _think_.

[DG: From what I can tell, if your RAM is under 256 megs, there's no problem,
but if it's >=256 megs, you have to reduce it quite a bit to get it to
work.  That's just from observation of comments from people with this
problem, though, no scientific basis or anything.

[SK: I've seen recommendations of -m90 and -m96 to get around memory problems]


B. Environment variables (the ones that seem valid for PPC)

    bmacplus          - can set bmac support to pretent a bmac
                        is a bmac+.  Could be useful for iMac
                        support, eventually, otherwise, not very
                        useful.
                        Value: =0|=1

    bus_speed_hz      - bus speed in Hertz, for clock speed.
                        Value: =40000000 or so, average...

    console_cache     - Improves video performance in X, but
                        fails on x100 machines, and crashes on
                        x100 AV machines.  (replaces -v)
                        Value: =true 
                        [DG: I don't think it checks the value, 
                        just the existence of the variable.]
                      
    cpus              - sets maximum cpus to use.
                         Value: =1|=2
                      
    max_wdunits       - allows you to disable high-numbered IDE
                        busses if they're empty, such as PB3400
                        with no CD-ROM.  Not necessary w/ PB2400,
                        whose second bus is disabled in source.
                        Value: =1|=2
    
    pb1400_expbay     - Expansion bay support (PB1400, replaces -e)
                        Value: =true 
                        [DG: Again, I don't think the value matters)
    
    scsi_nodisconnect - sets DEV_NO_DISCONNECT flag...
                        Value: =true 
                        [DG: Again, I don't think the value matters)
    
    scsi_sync         - sets DEV_RUN_SYNC flag...
                        Value: =true 
                        [DG: Again, I don't think the value matters)

Example of specifying multiple switches and environment variables 
  mach_options= -a -m90 pb1400_expbay=true bmacplus=0

David Gatwood marsmail@globegate.utm.edu
Edited by Steve Knouse knouse@neosoft.com
December 13, 1998