🚀 go-pugleaf

From: Stuart Friedberg  <stuart>

An Open Letter to Atari:

I would like to second a request that was made a few days ago.  Please,
PLEASE, make the high-performance (DMA) port on the "back" of the
32-bit TT a STANDARD SCSI interface.  Obviously, the interface on the
"front" to the ST will have to be the existing ST interface.  However,
I would say that the existing Atari hard disk is NOT a sufficiently
influential item to require the back end port to support the existing
drives.  Yes, I am suggesting that you do NOT support the existing hard
disks off the back of the TT.  (See postscript)

At least two of the third-party vendors of hard disks for the ST have
taken fundamentally complete SCSI interfaces and hacked them up to work
with the ST DMA port.  This is silly.  The ST should have come with a
STANDARD interface in the first place.  There is no reason to repeat
this mistake with the TT.

I have purchased one of the ST DMA -> mostly SCSI adapters sold by
these people.  These adapters are pretty much the boards they had to
stick into their drives to make the ST interface close enough to SCSI
to work with their drives.  (I am not mentioning names on purpose,
here).  However, because the adapter only has to make a particular
machine drive a particular disk, it is quite unreliable for driving
other, standard, SCSI peripherals.  I was very disappointed, because I
currently have access to a number of SCSI components, and none of them
will "fit" the ST well enough to make writing device drivers for them
anything but a waste of time.

There are now 400 and 800 Megabyte drives that plug right in to any
machine supporting SCSI.  (And a wide range of smaller sizes, as
well).  In many cases, these drives are CHEAP, because the use of a
smart SCSI controller in the drive allows the use of less expensive and
imperfect media.

I recommend you support the full SCSI spec, including the features
involving multiple bus masters.  By the time the TT design is pinned
down, there should be some VLSI chips out that do most of the grunt
work in implementing the full standard interface.  If by some chance,
you decide SCSI does not offer sufficient performance (unlikely for a
hobby/home machine!!), please investigate ESCI, which is another small
system peripheral standard.

Stu Friedberg  {seismo, allegra}!rochester!stuart  stuart@cs.rochester.edu

PS:  There are several reasons not to worry about the Atari hard
disks.  First, I suspect there are more ST owners with third-party
disks, with builtin SCSI interfaces hidden by the ST DMA adapter, than
ST owners with Atari's own disk.  They can convert by throwing some
hardware away.  (OK, it's not quite so trivial).  Second, the Atari
disks are small and slow (especially considering the price!) Third,
there doesn't seem to be any question that the entire disk structure
and file system will be radically different for the TT back end than
the ST GEM/TOS frontend, so there is no question of application or
driver software forward compatibility.  Fourth, instead of forcing
good-performance, standard drives to use a kludgy ST_DMA->SCSI adapter,
the existing Atari hard disks could be supported using a kludgy
SCSI->ST_DMA adapter, providing a reasonable upgrade path for ST owners
with an investment in a existing hard disk.