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Re: 35DP35 needs stiff +12 to avoid stuttering startups

Bob Bailin
Posts: n/a
      07-21-2008, 04:12 PM

"Chuck Olson" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed). ..
> I've been having a bit of trouble with recurring re-starts on boot-up. It appears as if
> hard drive spin-up might be pulling down the +12 enough to affect Quad CPU operation.
> With two 160 GB drives in a mirror raid array, start-up from Stand-by was undependable,
> with maybe 20 percent of the times interrupted , causing a full re-boot. Then I added a
> 500 GB third drive and that completely ruined any chance of start-up from Stand-by. Even
> full boot-up was interrupted with many automatic re-tries as each time the CPU shut down
> from glitches coming through on the +12.
> My PSU is a 500 watt Ultra, but the combination of its transient response, the wire
> resistance in the long run to the 2x2 power connector , and the sensitivity of the CPU
> regulator to variations on the +12, is just enough to cause serious problems.
> I decided to modify the wiring that's supplied on this Ultra PSU. There are two
> connectors furnished for CPU +12 - - a 4x2 with 4 yellow and 4 black wires, and a 2x2
> with 2 of each color crimped in and extended another 4 inches. The 35DP35 requires the
> 2x2 connector, so I decided to cut off the 4x2 connector and for each color take all 4
> wires of one color and solder splice them together with the 2 of that color to the small
> connector. This reduced the lead resistance to about 1/2 of what the 35DP35 saw before
> the modification. The result of this change turned out to be improved reliability of
> boot-up with all three drives running. It didn't get to the point where I can start up
> from Stand-by with regularity, but a full boot-up is no longer a problem.
> Maybe in some future version of this board, some provision for delay in spin-up of a
> third or higher drives can be elected in the BIOS in order to spread out the timing of
> disturbances in the +12, and of course, more pins in the CPU power connector and heavier
> wires from the PSU would probably help, too.

Or, you can buy a known quality PSU that maintains a stable voltage across
the full range of loads. PC Power & Cooling is one such manufacturer of
reliable PSU's.


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