Subject: Re:[netatalk-admins] Personal LaserWriter II at Linux Box

From: David Kelly <[email-masked]>
Date: Fri, 1 Aug 1997 12:34:01 -0500 (CDT)

Michael Stone <[email-masked]> writes:
> 
> Quoting Patrik Schindler ([email-masked]):
> > >NO! The DB25 connector is SCSI, it is NOT serial.
> > 
> > Not at the original LaserWriter II. The Only II-Series LaserWriter with SCSI was the IINTX and the IIg, AFAIK.

The original poster has to check his printer closely. You know what a
Mac disk icon looks like? There is one over the DB25 on the back of
every Mac since the MacPlus. The original LaserWriter had a DB25 for
serial. But every LaserWriter II I can remember has SCSI. No Personal
LaserWriter has SCSI except for those which had *only* SCSI for
connecting to the Mac. Those didn't have Postscript.

I just found a plain non-NT non-NTX LaserWriter II and looked. Didn't
see an icon for the DB25. Its suspiciously close to the LocalTalk
connector to suspect serial. There are 2 DIP switches beside it.
They could be used to select which port and what speed. Or they
could be used for SCSI ID.

> Two questions: First, why does a printer need a scsi interface? Also, 
> why did apple have to use DB25 for scsi? :-)

A Postscript printer really is a computer and OS. It has a filesystem
and a network stack. If a HD is attacted to a Postscript printer then
fonts and documents and other useful Postscript code can be cached
there were it wouldn't have to be uploaded again over a slow serial
or LocalTalk connection.

Apple used a DB25 on the original MacPlus because there wasn't room
for anything bigger and the current SCSI-II connector didn't exist.
Also, for original SCSI speeds the DB25 was Good Enough.

To this day Macintoshs still come with an external DB25 but that SCSI
bus is always limited to 5MB/sec speeds. My 8100/80 had (2) SCSI buses,
one internal only at 10 MB/sec, another hosted the internal CDROM and
connected externally thru a DB25. My new PowerComputing PowerCenter
Pro 210 still has a slow SCSI bus on the MB with a DB25 but has an
Adaptec PCI SCSI with internal and external connectors (SCSI-II) for
UltraSCSI speeds.

--
David Kelly N4HHE [email-masked] (hm)
======================================================================
The human mind ordinarily operates at only ten percent of its
capacity -- the rest is overhead for the operating system.

---

From: Sak Wathanasin <[email-masked]>
Date: Fri, 1 Aug 1997 23:31:38 +0100

In reply to David Kelly's message of the 01/08/97 at 12:34 -0500,

> They could be used to select which port and what speed.

I would guess that they correspond to the 4-position rotary switch on the
original LW and LW+. The 4 settings are: localtalk, serial 9600, serial 1200
and "special" (Diablo emulation). The "9600" is notional; as I mentioned in an
earlier msg, you can change the port speed via PS and store it in non-volatile
EPROM.

Sak Wathanasin
Network Analysis Limited
178 Wainbody Ave South, Coventry CV3 6BX, UK

Internet: [email-masked]
Phone: (+44) 1203 419996                    Fax: (+44) 1203 690690