Re: Coherent OS

From: Marko Mäkelä (
Date: 2007-11-12 21:34:55

On Mon, Nov 12, 2007 at 01:27:33PM -0600, Bo Zimmerman wrote:
> What I don't have is any idea of what Coherent looks like, due to
> aofrementioned power supply conversion woes.  Does anyone sell a
> high-wattage 110->220 step-up transformer that also remodulates to 50hz yet?
> Perhaps it's time to do another search of the internets...

Does the C900 really need the 50 Hz frequency for something, or would it
start up at 60 Hz, like all Commodore equipment I know?  If a
modification is truly needed, do you rule out an internal modification?

If the frequency change is truly needed and you do not want to solder
inside the C900, you might want to have a look at some second-hand
uninterruptible power supply (UPS) or variable-frequency drive (VFD).
They usually consist of an AC/DC transformer, a battery or capacitor,
and a DC/AC inverter.  Perhaps you could convince a 110V UPS to output 220V?
However, the output of most DC/AC inverters is far from a sine wave.
Some produce square wave (positive, negative, ...) or modified square wave
(positive, zero, negative, zero, ...), and some output triangle wave.
I would guess that the output of better VFDs and high-end UPSs is close
to sine wave.

Does your house have a 220V power outlet for a water boiler or something?
I've understood that in at least some parts of the USA, you can get
2-phase electricity.  Between the two phases, you would get around 220V.
In most parts of Europe, we have 3-phase electricity (about 400V between
phases, 230V between any given phase and the ground).

Finally, I would look for a 1:2 transformer that can handle several
hundred watts (yes, just plain old coils around a common core).
I believe that such transformers can be run in either direction
(to convert from 110 to 220 volts or vice versa).  I once tried to
start up the SuperPET that you sent me, with a 70-watt or so
transformer, but I did not use it for more than a few seconds, because
the transformer quickly got warm and started to smell.  Such
transformers are very heavy.

Around 1991, I installed a copy of some version of Coherent for x86,
from 5.25" floppy disks.  It was the first time I used an Unix-like
system, if a BBS run on OS/9 on a Motorola Exorset is not counted.


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