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From: neff@hp-vcd.HP.COM (Dave Neff)
Newsgroups: comp.sys.mac.hardware
Subject: Re: Deskwriter: serial vs PhoneNet
Message-ID: <1170011@hp-vcd.HP.COM>
Date: 30 Jan 91 18:26:57 GMT
References: <1991Jan25.102811.4724@usenet@scion.CS.ORST.EDU>
Organization: Hewlett Packard, Vancouver, WA
Lines: 31

> Dave's authoritative summary omits one important fact: you don't need to
> shell out for those ridiculously expensive LocalTalk connectors if you are
> just going to connect one Mac to one printer.  A plain "null modem" RS232
> cable will do just fine.  (Your Apple dealer will sell you one if you ask
> for an ImageWriter II cable; they're about $10.)

True with ImageWriters and LaserWriters but not true with DeskWriters.
DeskWriter only goes into LocalTalk mode when the isolation transformer
is installed.  This "auto lan detect" feature was added as an intended
ease of use issue and we knowingly eliminated the ability to use 
"direct connect LocalTalk" with the DeskWriter.  The fact that serial
and LocalTalk gives comparable performance was one reason we saw no
real need to support direct connect LocalTalk.  That is, if you have
a serial cable, just use serial mode, if you have LocalTalk connectors,
then and only then you can use LocalTalk mode.  In fact, the DeskWriter
will automatically sense the cable and go into the proper mode.
O.K., and I confess, the hardware to do the automatic lan detect
was cheaper than adding a DIP switch :-).  We also didn't have any
cutout to mount a DIP switch and didn't have any general front pannel
to allow manual selecting of the IO.  Hence the automatic lan detect
seemed like a good feature -- despite the inability to do direct connect
LocalTalk.

As for CPU speed being an issue, the CPU speed is not an issue with
the IO, it is an issue with the DeskWriter driver.  On slow Macs the
driver cannot keep up with either IO.  That was my point.  If you
have a slow Mac (Classic, Plus, SE), the speed of the DeskWriter will
generally be limitted by the driver, not the IO or printer mechanism.

Dave Neff
neff@hpvcfs1.HP.COM