[TUHS] Mach for i386 / Mt Xinu or other

[schily@schily.net (Joerg Schilling)]

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Diomidis Spinellis <dds at aueb.gr> wrote:

> > Writing CDs is a highly complex task. No known kernel is able to do that
> > internally.
> >
> > So the only useful method is to use SCSI pass through.
>
> This is an interesting point.  However, controlling the C/A/T 
> phototypesetter 20 years before writable CD-ROM appeared, was also a 
> very complex task, yet it was accomplished through a simple device file. 

Well, it used a serial or parallel connection on top of a standard driver.
I cannot speak for a real C/A/T device, but I know the Berthold 
phototypesetters that use a serial line with a nearly identical interface
and C/A/T probably was a clone of a Berthold phototypesetter.

In the C/A/T case, troff has the knowledge about how to talk to the 
phototypesetter and uses a "pass through" UNIX driver to transfer the data.

For the CD writers, please keep in mind that during the time when everybody 
used them, there was a constant development on the SCSI command interface for 
the devices and many of the drives had massive firmware bugs. 

cdrecord does always include support for all recent drives and implements 
workarounds for the firmware bugs. Do not expect that people in the UNIX kernel 
area would ever react in time and do not expect that potential abstraction 
layers from the CD drives would be compatible amongst different UNIX versions.

Have a look at a similar problem from 1969:

	There was only one IMP and a set of IMP<->computer adaptors for every
	possible "computer" system.

The IMP<->computer adaptor is similar to the lowest layer of my libscg.

Above that layer in libscg, everything is portable and unified.

Jörg

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