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5V line is most critical supply. Could a simpler mod be done that just provides clean 5V line from linear PSU

219.73.73.54

In Reply to: RE: gdrv off but no change in current consumption, 1394..... posted by cics on June 13, 2010 at 12:32:26

As far as possible linear supply in place of PWM PS is concerned, the 5V line is no longer critical. The concerns are large current supplies for the QPI (@1.1V) and possibly the CPU(@0.7V). At such low voltage, normal 3 terminal regulator circuit cannot work. A work around is to use a negative voltage to generate low voltage.

Heat disspation is also a concern which is assocaited with the raw DC voltage. A 6V battery supply or 5V power source would be to high as the regulator would dissipate 13W and 12W of heat respectively - a waste of energy and case temp wiould rise. A Low dropout regulator such as LT108X together with a low raw DC voltage, say 3V(or 3.3V Lithium Battery packs), would appear optimial.

I will build two low voltage regulators to test the QPI and CPU.

Follow Ups:

RE: 5V line is most critical supply. Could a simpler mod be done that just provides clean 5V line from linear PSU - cics 10:44:52 06/14/10 (2)
Your current approach is superior. I'm looking for an easier way to get say 80% of benefits. Critical chain is:

RAM > QPI link > H55 chipset > PCI or USB

These components all share 5V line. What I'm thinking of is a 5V replacement supply at P24 connector. Possible?
- RE: 5V line is most critical supply. Could a simpler mod be done that just provides clean 5V line from linear PSU - jackwong96 10:54:44 06/14/10 (1)
  Please elaborate more on your idea of a 5V replacement supply at P24 connector. Do you mean replacing the ATX 5V with a linear regulated 5V supply?
  
  I'm think of an idea to use the P24 3.3V to feed a QPI linear regulator, presuming that an ATX PS is to be used. The 3.3V line has very light current loading. By doing so, the P24 5V will be greatly relieved and the interference between the QPI load and Ram etc would be greatly reduced.
  
  Edits: 06/14/10
  - RE: 5V line is most critical supply. Could a simpler mod be done that just provides clean 5V line from linear PSU - cics 11:22:22 06/14/10 (0)
    Do you mean replacing the ATX 5V with a linear regulated 5V supply?
    
    Yes. This would power the main audio streaming/signaling chain. Other components including CPU have a secondary role.
    
    Using 3.3V line for QPI is very interesting and would reduce 5V load significantly.

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