TO:   ALL
FROM: RON PERRY
RE:   DOS OSD
DATE: 3/20/89

In attempting to put together a presentation for the DOS OSD,
I've come across three areas of concern. If anyone can offer
an opinion or assistance, please leave a message on the BBS or
contact me directly at (408) 439-2310.

1 - Do we need any special protection for requests from background
    tasks (PRINT, NETWORK)?

    It seems to me that such programs supply there own protection.
    Since DOS is not re-entrant, a network or print spooler must
    protect against re-entering DOS. At the same time, these programs
    require file services that must come from DOS. PRINT.COM latches
    serveral software interrupts and either protects from re-entry by
    semaphores or by special knowledge of DOS ('safe to enter flag')
    and requests DOS servicing when the (printer) interrupt occurs
    (if it is safe to do so) or from a timer interrupt at some time
    later (when it is safe). I assume this is also true of networks
    that run under DOS. (???)

2 - Is there a need to latch Interrupt 13 and re-direct (translate)
    requests through a SIM if the boot device is attached to a CAM
    HBA?

    The HBA attached itself to Interrupt 13 during sytem initialization
    and must obviously handle interrupt 13 interface otherwise DOS would
    not boot. The OSD has to know that the boot device is attached to both
    interrupt 13 and a CAM HBA so that the device doesn't get configured
    twice (as an interrupt 13 device - unit C, and as a CAM device driver
    device - unit D) (unless someone knowns a way to safely 'unhook' the
    boot device from interrupt 13).

3 - Should we use a configuration file to initialize CAM?

    If the DOS OSD as a pseudo device driver during system initialization,
    then following Shashir's proposal, the DOS OSD
    would then locate SIM modules in ROM, and / or load SIMs from
    the boot device as required. The names and any parameters associated
    with loaded SIMs can be passed on the command line, however there
    may be a limitation on the length of this command line. An alternative
    to the command line is to load a configuration file which supplies the
    name of SIMs and associated parameters.

    In either case, I think there is a requirement to pass configuration
    information from the OSD to the SIM. The current initialization
    proposal deals with the SIM passing initialization information to the
    OSD (via the Initialization Table). A SIM / HBA may want to be told
    its base port address, dma channel, irq line, etc without trying to
    self determine its configuration.