From:    James McGrath
         ANSI/IEEE/PCMCIA Liason
         Quantum Corporation
         500 McCarthy Blvd
         Milpitas, CA 95035
         408-894-4505

To:      Dal Allan
         Chair, Small Form Factor Committee

CC:      John Reimer
         Chair, PCMCIA

         Martin Freeman
         Chair, IEEE Disk Attach Study Group

Date:    May 8, 1991

Subject: Using a PCMCIA Interface on a 1.8" Winchester Disk Drives



On Tuesday, May 7, the Board of Directors of the PCMCIA was scheduled
to approve the concept of making provision in the PCMCIA standard for
winchester disk drives to incorporate a PCMCIA interface.  This
clears the way for specific proposals to be offered to the Marketing
and Technical committees of the PCMCIA.

The Marketing committee has already established a working group to
define the requirements of winchesters with respect to the PCMCIA
interface - John Reimer is heading this effort.  The Technical
committee already has a committee for I/O cards.  This is the natural
forum for initial technical proposals, although there may eventually
be a need for a working group dedicated to winchesters.

Although I plan on being the focal point for technical proposals, I
anticipate active input by members of the ANSI and IEEE communities
in the formulation of these proposals.  Towards this end, I will be
proposing topics for discussion with the Small Form Factor committee,
ANSI X3T9.2, and IEEE Disk Attach Study Group as appropriate.  I will
also feel free to coop the assistance of members from these groups
for specific topics.

The PCMCIA requires at least three showings of a topic at different
meetings before adoption.  Therefore I propose that our efforts begin
with the June meeting, targeting completion at the November meeting.
The first item of business should be the outlining of topics that
must be addressed and the formulation of draft proposals for June.

The June meeting is on Monday and Tuesday, 24 and 25, in Seattle.
Microsoft is the host.  For more details, please contact the PCMCIA
office in Sunnyvale, CA.




My own experience and knowledge leads me to propose the following items:

    Adoption of the PCMCIA connector for the two piece, removable
    device, connector in the Small Form Factor Standard for 1.8"
    drives.  I would advocate this also be considered for 2.5"
    drives.  I also recommend that no 50 pin option be defined
    since it does not provide significantly greater functionality to
    justify two pinouts.

    Coordination of efforts between ANSI/IEEE/PCMCIA on defining 
    future, higher pinout connectors (e.g. 100 pin connectors).

    Arrangement of the pinouts for IDE and SCSI so that
    PCMCIA/IDE/SCSI drives can be plugged into sockets supporting
    PCMCIA/IDE/SCSI without damage (i.e. coordinate power and
    ground line usage).

    Allow a host/drive manufacturer to, in the future, supply a
    system/drive that can support IDE/AT/SCSI by field configuration
    (e.g. a jumper).  We have discussed this for IDE/SCSI, and should
    extend it to include PCMCIA.

    Devise a Type III PC Card defining a new mechanical form factor to
    accommodate larger devices.  Given the needs of winchesters and
    the dimensions required to support PC Card bays with two cards
    stacked vertically, 10 to 12 mm is a natural range for the
    height.  54 mm is a standard width, although the requirement for
    guide rails must be considered.  Currently, the winchester length
    (73 mm + 5 mm for edge connector) is shorter than the PC Card
    length (85 mm, including the connector), so we may wish to
    consider lengthening the drive standard to match.  Finally,
    various environmental specifications must be agreed upon.

    Define the required software support for winchester disk drives.
    PCMCIA defines control/configuration register set that may need
    some extension for winchester support.

    Allow for support of P1212 as an extension of PCMCIA (and PCMCIA
    as an extension of P1212).  This promotes interchange between
    platforms using these different standards.

    Define a burst mode functionality to allow for rapid access to
    data separated by pauses in the range of sevral microseconds.

    Define a DMA capability.  Empathisis should be on third party
    DMA (device is a slave).  First party DMA currently looks both
    too hard and not needed (systems needing it can afford a DMA
    controller on board).

    Define the requirements for using PCMCIA memory - not I/O - card
    standards for access to winchesters buffered by semiconductor
    memory.

I will attempt to coordinate the activities between PCMCIA, ANSI, and
IEEE.  However, I will require the assistance of the rest of others
in order to draft acceptable proposals.