From: ktyra@rock.concert.net (Kristopher L Tyra -- The Sapphire Group)
Newsgroups: comp.unix.aux
Subject: Re: CD ROM drive to install A/UX 3.0
Date: 7 Jan 93 01:05:19 GMT
Organization: CONCERT-CONNECT -- Public Access UNIX

In article <C097Is.9L3@acsu.buffalo.edu> yaosenko@acsu.buffalo.edu (Yaosen Ko) writes:
>In article <1993Jan1.220643.942@grebyn.com> mfraioli@grebyn.com (Marc Fraioli) writes:
>>In article <-r#@byu.edu> parkj@bones.et.byu.edu (John R. Park) writes:
>>>I looked in the FAQ list for the answer to this question
>>>but I didn't see it.  Can anyone tell me if any NEC CD-ROM
>>>drives will work for installing A/UX 3.0?
>>>
>>>
>>Ours doesn't.  :-(  I forget the model number of it, but we had to
>>borrow an actual Apple CD-ROM drive to install from.
>>
>
>I believe all NEC CD-ROM drives are not compatible with A/UX.

Sorry I haven't had time to post this earlier.

This is an official announcement of release for the producut NHD.

NHD (New Hard Driver) is a an object-oriented device driver that supports
every major drive type that I know about (include NEC's).  The problem with
the NEC drives are that they don't allow the drivers to change the physical
block size of the device.  A/UX Generic Driver (GDISK) only supports 512 bytes
per block.  NHD supports any block size that the drive supports.   NHD has
many other features. some of which I will list here.  Even if you don't have
a problem CDROM, NHD is more efficient and slightly faster then the A/UX 
driver.   NHD is avaialable via anonoymous ftp from jagubox.gsfc.nasa.gov.

                       New Hard Driver (Release 1)
                       ___________________________


       New Hard Driver is an Object-oriented hard disk  driver
       that  is based  upon  a  new  generic  driver  package known
       as Gears SCSI Driver (GSD).  The Gears  SCSI  Driver
       replaces  Apples  Generic Driver  (GDISK).  This  new
       generic driver supports the following features:


       *  Infinite disk capacity (w/Parallel Access)

       The GDISK driver supported  by  Apple  Computer,  Inc.  does
       not provide support for more than one media type in a drive.
       Furthermore,  parameters for more than one disk cannot be
       maintained in memory and attempting to do  so  using GDISK
       is difficult to sometimes impossible.  GSD  supports
       multiple  media  on  one drive.  Furthermore, this media can
       be swapped in an out by the non-generic side of  the device
       driver even while the media is currently mounted.

       *  Removable Media support

       GDISK does not support removal and re-insertion of media in
       a drive.  GSD supplies routines for the non-generic side of
       the  driver  to  support removable media.

       *  Multi-sized Block Support

       The current generic driver only supports 512 byte blocks.
       GSD supports any block size needed.  Furthermore, the
       blocks  sizes  may  change  due  to changes in media type
       (i.e., removable media).

       *  Sophisticated Error Handling

       GDISK does not allow the non-generic side of the device
       driver to override error messages.  Unfortunately, in many
       cases it reports errors that should not be reported.  GSD
       provides  a  much  more  sophisticated   error   handling
       technique that allows the non-generic side of the driver to
       control the error reporting.


       *  Removal of Alternate Bad Blocking

       GDISK was designed at a time when many disks did  not
       support hardware bad blocking.  This lead to an alternate
       bad blocking scheme to be added to GDISK which has  added
       runtime  overhead   to   the   driver.    However,
       spare'ing(hardware bad block mapping) is now standard for
       all SCSI hard drives;  therefore, the alternate bad blocking
       is not required.  GSD  does  not  support  the  alternate
       bad blocking technique.


       *  Read-only support

       Although a patch does exist for CDROM technology,  GDISK
       does not actually support read-only drives.  This is because
       the driver always  attempts to write the DPME (partition
       table) structure on to the drive.  However, this is not
       acceptable to WORM technology.  GSD supports true "hardware
       read-only" as well as "write-once" drives.  Furthermore, GSD
       supports techniques that allow searching  for write protect
       indicators which the GDISK due to its  delayed
       initialization  does  not support.


       *  Multiple Driver Support

       The current version of GDISK is resident in the device
       switch table of A/UX.  Furthermore, this interface does not
       provide a  mechanism  for routing to the correct device
       driver upon determination of a foreign  hardware  type.  GSD
       uses a patching routine to replace the current  interface
       with  an  interface that allows a routing mechanism.  This
       mechanism requests a simple inquiry from  the hardware and
       lets the routing function call the proper  driver.
       Furthermore,  once the driver has been determined the device
       switch table  is  patched  (at  runtime) with the correct
       driver routines.

       *  Re-implementation of the disk sort algorithm

       The current version of GDISK  does  not  correctly  sort
       disk requests on the queue when such requests are DMA
       controlled.   This happens  because  the buffer cylinder
       member variable is filled with the address of  the  DMA
       request  and therefore correct sorting will not happen
       during these requests.   GSD requests requests are broken up
       into a partitions therefore cylinder information is  not
       needed  and just the block number can be specified to the
       sort algorithm.  The sort algorithm is also inline code.


       Some of the features of GSD are not used by the  NHD  driver
       and some  will  be  used  in  future  releases.   However,
       the  most important to CD-ROM owners  is  the  multiple
       block  size.   NEC Drives  do  not support the MODE SELECT
       parameter to change block size.  This is an optional command
       in SCSI so they do not need to support  it.  However, GDISK
       requires the command in order to get the device to a 512
       byte  block.   Since  GSD  does  not  require changing  the
       block size, no MODE SELECT is performed and the end result
       is NEC Drives work.

       Since this is a real product which is sold to development
       shops I have  only included binary only.  If your firm
       requires source or specific drivers please contact me.


                                ________________________________
                                Kristopher L. Tyra
                                The Sapphire Group
                                (919) 481-9052
                                ktyra%saphire@concert.net
                                Consultants - A/UX, OSF, AIX/ESA,
                                              Sun, X-Windows, MacOS
Newsgroups: comp.unix.aux