Re: CD-ROM block size

[Steffen Nurpmeso <steffen%sdaoden.eu@localhost>]

Dima Veselov wrote in
 <Zoz2CnYeglHqoxbm@gloria>:
 |>> Greetings!
 |>>
 |>> I wonder is there a way to know blocksize of
 |>> CD-ROM? I have a number of old machines required
 |>> to use 512-byte SCSI CD-ROM and I want to ensure
 |>> 512-byte mode is enabled or supported.
 |>>
 |>> I tried atactl and it shows wrong block size,
 |>>  always reporting 512, >> even on certainly 2k
 |>> CD-ROM.
 |>
 |> This mostly matters for the firmware and for
 |> booting from CD-ROM. The physical media is always
 |> 2048 byte sectors but some drives can enable
 |> emulated 512-byte access with the SCSI MODE
 |> SELECT command. Good drives for both Sun and
 |> DEC are the Toshiba XM series.
 |> These resources might be useful:
 |
 |Thank you for the answer. I guess real question
 |was then - how one can find that drive is able tp
 |emulate 512-byte access? Is it possible to question
 |SCSI or test it somehow in the running system?

I have used SCSI-mmc3r10g.pdf to implement my s-cdda.c.
It says "512 is obsolete", but also says

  The block descriptor associated with the Mode Select and Mode
  Sense commands is used for legacy system support. If supported,
  block sizes (see Table 343.) shall include 2 048 and may include
  512, 2056, 2 324, 2 332, 2 336, 2 340, 2 352, 2 368, and 2448
  bytes.  Table 343 shows the implementation of the various block
  sizes. These definitions apply for all READ commands. For READ
  (6), READ (10), READ (12) when Block Descriptors are not
  supported, block size shall be 2 048. Other block sizes are
  allowed and the contents of the blocks are not specified by this
  standard.

  Table 343 – Block Descriptor Block Sizes for Read
  Bytes   Readable block types
  512     Mode 1 or Mode 2 Form 1 sectors divided into four blocks each

SCSI-mmc3r10g.pdf can be searched for free.  (I could give you an
URL if all else fails.)

--steffen
|
|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)