re: Twilight Zone type of problem with games, IDE HD and mouse wheel! :)
Monday, April 18, 2005 at 7:29 pm
Windows XP Annoyances Discussion Forum
Posted by Jack Gulley
(5917 messages posted)
Gee. You listed the specifications and talked about every thing but the most logical
thing that is causing the problem!
The problem is your POWER SUPPLY and its +12v power distribution!
I bet you have a CD-RW and/or DVD/RW in there that forgot to mention. Plus a few
FANS and maybe some neon lights running off of +12v. But with two disk drives (and
maybe some CD/DVD drives) and all that hardware on a P4 processor, plus that Video
card, your system is going to draw a LOT of current at +12v. The "weak" point of
most cheap power supplies.
Here is what happens. When you roll the scroll wheel, the processor loads down
sending commands to the video graphics adapter to start scrolling the screen up/down.
This processor activity starts loading down the power supply some. The Graphics Processor
then goes into overdrive moving all that data around, and it in turn starts drawing
a large amount of current. That is why they get hot and have to have a fan. This
huge increase in load on the power supply forces it to redirect more of its power
to the critical +5v and the voltages to the processor, system board and video adapter.
Because the +12v is less critical and less regulated, input power is taken away
from it and shifted to the other voltages, causing the +12v to drop slightly. With
a slight lag, this voltage drop causes the fans and motors running off of it change
speed and in so doing, draw even more current on the +12v. On some machines you can
actually hear the power supply fan change speed when scrolling the screen up and
down this way. Actually what you are hearing is the change in beat frequency between
different speed fans. All this current draw takes the +12v down just a little more
and induces a little ripple on the +12v as the power supply struggles to recover
from the change in loads. After some delay, it recovers and is able to bring the
+12v back into regulation.
But guess what the most sensitive device in the system to +12v ripple is? You
guessed it, the disk drives. When they see the +12v drop to far and then ripple on
the voltage, they start cutting back their power draw on +12v, and the only way
they have to do this is cut back power to the motor control logic, which causes their
motors to spin down. It is normally the last drive (least used) drive that will start
to spin down first.
Now complicate this with the fact that most of the wires going to the disk drives
are too small of a gage and too long to carry current when there is ripple on it,
and most power supplies have several connections drawing current on each leg out
of it, no wonder the disk drives are spinning down.
If you look at the top of the line power supplies sold, they have a higher rated
maximum current on the +12v than do most other power supplies. In addition they usually
have only one connector that can plug in to a disk or CD-Rom drive per leg and have
more legs out for this, plus a heavier gage wires, so that current draw and ripple
are not such a problem.
OK, so what can you do? Well you could get a much better power supply, one rated
at a higher output with a lot more current (amps) on the +12v. And that has more
legs out of if for powering drives, fans, etc. The quality of power supplies is judged
more by their total weight than by their price. OR, you can try to make sure nothing
else (fans) is plugged into the legs going to the disk drive. You can turn off some
of the load on the +12v if you have neon lights in the box and extra fans. Maybe
even unplug a DVD or extra CD-RW drive. You can even help the power supply by using
a good quality power cable to it (instead of the cheap small gage wire ones that
come with some systems). And make sure it is plugged directly into a wall outlet
or heavy gage distribution box, and not hooked up through some cheap long extension
cord and switch box. A good quality UPS box sometimes helps as they usually have
heavy gage short cables.
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 |  | re: Twilight Zone type of problem with games, IDE HD and mouse wheel! :) (Jack Gulley: Mon, Apr 18, 2005, 7:29 pm) |
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