Re: Zip on a IIgs

[Rubywand <rubywand@swbell.net>]

Sheane and Bonnie Meikle writes ...
> 
> --
> 
> Rubywand <rubywand@swbell.net> wrote in message
> 38B24CB9.BF7F4EE9@swbell.net">news:38B24CB9.BF7F4EE9@swbell.net...
> > Supertimer writes ...
> > >
> > > "Sheane and Bonnie Meikle" <action1@telusplanet.net> wrote:
> > >
> > > >Ok after buying Macs so I could transfer data
> > > >easily from my PC to my II's I
> > > >finally won a scsi card on ebay today.
> >  ....
> > >
> > > On the hardware side, which Rev C card is it?  Apple or RamFAST?
> > > The Apple card does not supply termination power and neither does
> > > the Zip drive, so you need to attach another hard drive or a CD-ROM
> > > to the same SCSI chain to supply the power.  The RamFAST card
> > > supplies termination power so you do not have to worry about it.
> >
> >  ....
> >
> > There is an easy mod to add term power to the Apple Rev C SCSI card.
> > A pic showing the modification is available on Ground at ...
> >
> > ftp://ground.ecn.uiowa.edu/apple2/Docs/revc.gif
 ....
> 
> Does the terminator switch on a zip 250 not provide 
> enough termination? I do
> intend to add a CD player to the GS as I have a burner on my PC and would
> like to make some CD's for the GS, but that's down the road.
 ....

     I do not know about a "zip 250". If it is a modern Zip Drive, it
probably does not supply termination power. The switch you are talking about
is, most likely, the usual Termination ON/OFF switch.

    "Termination" is not the same as "Termination Power". Termination is a
resistive load normally placed at the end of a chain of SCSI devices. Its
purpose is to stabilize the SCSI lines (e.g. reduce 'ringing', reflections,
etc.).  Every SCSI device should have a Termination switch to turn ON (or
Termination 'pack' to plug in) in case it happens to be connected at the end
of the chain.

     Termination Power is a kind of bias placed on SCSI lines to, in
combination with the Termination load, stabilize the lines. In olden times,
it was normal to have SCSI hard drives which supplied Termination Power as
well as Termination.

     Since the early 1990's, it has become standard practice to expect the
SCSI interface to supply Termination Power. Few modern SCSI drives are likely
to supply it.

     You _may_ be able to use a Zip Drive without having Termination Power;
but, it does not seem like a good idea.




Rubywand