#UK Amiga in the U.S.
15 messages in this thread
I have been offered a to year contract in the U.S. , can any one tell me
whether my sons UK Amiga A600 will work in the U.S. if I purchase a U.S. power
supply ?
Many thanks
Iain Wilson
Not that I am an expert in the Amiga field, but I know you have to deal with
the fact that, in the UK, you are running on 220v, while we run on 110. Also
be aware that your power comes in at 50hertz, while we have a 60hertz line-
such is the case that you may have to deal with resetting your clock every once
in a while, but other than that, I have heard of no other "spikes" or pitfalls
going across the ocean with a computer…although I have not done so myself.
Does anyone else have first-hand knowledge?
Steve,
Many thanks for the message, do you know whether I would have to take a UK
(PAL) T.V. rather than NTSC (No Two Colors The Same !).
Many thanks
Iain ~~~~
NTSC – My version is "Never Twice the Same Colour (or Color)"
If it's a ECS machine (rather than OCS) it should work on both PAL and NTSC
systems. Which is it (OCS or ECS)?
Mat (in the U.K. too (don't seem to be many of us about on here…))
Mat ! There are a few of us in the UK !!!! Steve Gardiner – Sipping afternoon
tea in London
"Sipping afternoon tea in London" –
Well, I've kissed goodbye to London for the moment (but definitely not the
tea…)
Next rendevous – Manchester!
Why should changing to 60Hz mean you have to "reset the clock once in a while"?
Yours puzzled,
Mat.
Michael,
the internal clock updates itself using the same signal that times the
horizontal sweep of the display. Since this is a different rate, on each
side of the pond, there are two different versions of the chip. Normally,
this wouldn't be a problem.
However, if you take an Amiga designed to run off of 50 Hz to a country
where the incoming power is running at 60 Hz, your internal clock will be
running 20% faster than normal. Short of changing the chip, there is no
real reason to swap out the chip (and it would be difficult to obtain with
the way things are now, anyway). Just live with it until you get home.
"You do trust me, don't you? Of course you do."
— "To Play the King" (BBC)
The signal which times the horizontal sweep of the display is
unrelated to the power supply frequency, though if you are running on
an NTSC system in the U.S., by coincidence (or more probably design)
NTSC signals and U.S. 120V mains power both run synced to 60Hz (but
NOT synced to each other). Similarly, PAL signals and British 240V
mains power coincidentally both run at 50Hz.
Power supply frequency _cannot_ have any influence on Amiga timing as by the
time the power has passed through the power supply it is running at DC anyway!
Amiga displays can run at any frequency between (please correct me) 15Hz (for
A2024) up to 72Hz (or perhaps more). Hence, it would be madness for the Amiga
operating system to set its timers relative to these frequencies!
Disclaimer – I am probably wrong.
Yours,
Mat.
Michael,
if you look at the schematics, one of the signals generated by the
power supply is TICK, which is exactly at the same frequency as that of
the input power signal. TICK is normally used as the TBASE signal for
marking the passage of time. BTW, it is possible to use the _VSYNCH
signal in place of TICK, if your power supply drops TICK, but it is not
quite as accurate, and it happens to come from the video section.
In any case, if you run 60 Hz power into an Amiga set up for 50 Hz
TICK, you will get a fast clock. Hmmm, it might be possible, if it's on
that motherboard, to switch to using _VSYNCH. That's a thought, since it
will be 50 Hz no matter what.
What you might want to do is see if you have a jumper on the
motherboard near one of the 8520's, or find someone that knows the exact
jumper for your machine. I don't have a schematic for yours. In either
case, you may want to switch it to use _VSYNCH for the duration of your
stay here. It's not exactly accurate, but much more accurate than that of
a TICK derived from 60 Hz.
BTW, mostly wrong <g>. I've only chased this signal around the
schematics a half dozen times, or so. It was a common problem, at one
time, for a whole series of A2000's; TICK would die in the power supply.
"You do trust me, don't you? Of course you do."
— "To Play the King" (BBC)
Brian,
Looking at _my_ schematics (for A500+) the power supply produces no such signal
(only giving +/- 12V, 5V and ground outputs). Absolute calendar time is stored
by the battery backed clock (bolted on as standard in the '+, optional in the
earlier models (pre-revision 8)), which has its own 32768Hz oscillator. This
real time clock is read at each boot up (SetClock LOAD) into a software clock
operated by AmigaOS, and synced to the system timer chips.
I'll have to take your word for info on the '2000 TICK signal, but on the A500,
due to the power supply spec, this must be created internally (as far as I can
tell).
The original creator of this thread was enquiring about an A500 (if I remember
correctly), so if you are reading this, listen to _me_, not Brian 🙂
Yours A500'ly,
Mat.
"New Disclaimer: I'm mad, stupid and know nothing. Hurrah!"
Mat,
I finally found my schematics for the A500. Yep, sure enough, you are
correct. Unless something funky is going on is the 500, the clock is
locked to _VSYNCH which is generated by Agnus, so changing the input
frequency shouldn't make one wit of difference. For an A2000, yes. For
an A500, nope. BTW, changing to _VSYNCH should fix the same problem for
an A2000.
"You do trust me, don't you? Of course you do."
— "To Play the King" (BBC)
I don't know about current models, but I know the clock on an A1000 was
affected by input power freq. I know this because, when I bought it I was
stationed in Japan with the Navy. On the base we had 120 volt, 50 Hz
power. I kept noticing that, under early versions of the system software
(either WB1.1 or 1.2 or both, I don't remember), my clock ran exactly 10
seconds slow per minute. When I received an upgrade (either 1.2 or 1.3),
the problem went away. I read somewhere that the upgraded system software
could detect input power frequency and adjust the clock accordingly.
This seems a rather reasonable thing to do to me. Why build an
oscillator for your clock circuit when you have a steady oscillating
signal available for free.
._ _ _ INTERNET: mshea@math.arizona.edu
| | |ichael _>hea COMPUSERVE: 76665,3360
It sounds like in earlier versions of AmigaOS the real time clock was sync'ed
to the VBlank Interrupt (which is 50Hz on PAL Systems and 60Hz on NTSC
Systems).
On later versions, I suspect, the clock is sync'ed to one of the CIA timers,
which are independent of VBlank frequency.
As far as actual power supply frequencies go, this is irrelevant from a timing
point of view, as by the time power reaches the Amiga's PCBs it has been
converted to DC (5 and/or 12 volts) by the power supply.
Also, I would doubt that the power supply frequency you get is _exactly_ 60Hz
anyway. Certainly in the U.K., power supply frequency (and voltage for that
matter), may vary by up to +/- 10% around the quoted 50Hz / 240V (or even more
if you get a power cut 😉
Of course, I could be wrong on all these points!
See ya,
Mat.
Michael,
I believe the 60 Hertz signal is about the ONLY accurate thing in US
power.
DJ