[Coco] high-density disks

[Joel Ewy]

Chuck Youse wrote:
> Seems I can't find an appropriate density bit for IT.TYP in my 3.5"
> high-density floppy disk descriptor.  There's DNS.FM and DNS.MFM - which
> are used for single and double density, respectively.  In my case I need
> to distinguish between 250KB/s (standard MFM) and high-density
> (500KB/s), depending upon the drive attached.  Any ideas folks?  New
> DNS.blah for high-density (which I believe is _still_ MFM, technically,
> which means we'd have yet-another-misnomer to deal with)?
>
> C.
>
>   

FWIW, here's how it's done in OS-9/68K.  The descriptor has a 'rates'
field in addition to density.  Following is the output of 'dmode /d0' on
the MM/1, where /d0 is a high-density 3.5" disk, and the help file for
dmode, which describes the descriptor bits:

name=d0
 drv=0 stp=3 typ=$26 dns=$03 cyl=80 sid=2 vfy=0 (on) sct=37 t0s=37
 sas=8 ilv=2 tfm=0 toffs=0 soffs=0 ssize=256 cntl=$0000 trys=7 lun=0
 wpc=0 rwr=0 park=0 lsnoffs=0 totcyls=80 ctrlrid=0 rates=$30
 scsiopt=$0000 maxcount=65535

    
    drv      Drive Number  0...n
    stp      Step Rate     0 = 30ms, 1 = 20ms, 2 = 12ms, 3 = 6ms (5")
                           0 = 15ms, 1 = 10ms, 2 = 6ms, 3 = 3ms (8")
    typ      Device Type   bit0 - 0 = 5"   1 = 8" (old method)
                           bits 0-4 (new method)
                               3 = 8"  4 = 5"  6 = 3.5"
                           bit5 - 0 = OS9  1 = DD trk 0
                           bit7 - 0 = flop 1 = hard
    dns      Density       bit0 - 0 = SD   1 = DD
                           bit1 - 0 = 48   1 = 96 tpi
    cyl      Cylinders
    sid      Sides (heads)
    vfy      Verify (0 = yes)
    sct      Sectors/Track
    t0s      Sectors/Track on track 0
    ilv      Interleave
    sas      Segment allocation size
    tfm      DMA transfer mode
    toffs    Track base offset
    soffs    Sector base offset
    ssize    Sector size
    cntl     Control word  bit0 - 1 = format inhibit
                           bit1 - 1 = multi-sector
                           bit2 - 1 = device has stable ID
                           bit3 - 1 = device tells size (SS_DSize)
                           bit4 - 1 = device allows 'format track'
    trys     Retries (0 = no retries)
    lun      SCSI logical unit number
    wpc      Write precomp start cyl
    rwr      Reduce write current start cyl
    park     Park cyl number
    lsnoffs  Partition start sector
    totcyls  Total cylinders on device
    ctrlrid  SCSI controller ID
    rates    Transfer rate bits 7-4            3-0
                            0 = 125 Kbps   0 = 300 rpm
                            1 = 250 Kbps   1 = 360 rpm
                            2 = 300 Kbps   2 = 600 rpm
                            3 = 500 Kbps
                            4 =   1 Mbps
                            5 =   2 Mbps
                            6 =   5 Mbps
    scsiopt  SCSI options  bit0 - 1 = assert ATN supported
                           bit1 - 1 = target mode supported
                           bit2 - 1 = synchronous transfers ok
                           bit3 - 1 = enable SCSI parity

JCE

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