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Can anyone tell me ?Why p1,p2...is written to the different cable.kindly let me know the idea.any help would be highly appreciated.

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A short, practical explanation tied to the replies above:

The P1/P2/etc labels are simply pin numbers on the drive power plug (the SATA 15-pin power) — they are not separate “cables.” The pins are grouped so a drive can get multiple voltage rails (and multiple conductors of the same rail) and so the connector can implement safe power sequencing. That sequencing (sometimes called precharge or staggered mate) ensures ground and logic rails make contact before high-current motor rails, reducing inrush and avoiding damage.

Why a 3.3V rail exists: it is provided because some modern device electronics and optional features use a low-voltage rail. Many consumer drives do not actually use 3.3V, so they work fine when an adapter does not provide it. However some drives implement a “power disable”/control function tied to that rail; if the 3.3V line is asserted by a backplane the drive can stay powered down until that signal is removed. That is why a drive that otherwise looks fine might not spin up on certain backplanes or adapters.

Why different wire colors: color coding is a standard to avoid wiring mistakes. Typical ATX color conventions are orange = +3.3V, red = +5V, yellow = +12V and black = ground; older 4-pin Molex peripheral plugs use yellow = +12V, red = +5V and two blacks for ground. Colors make assembly, troubleshooting and safety checks faster.

Practical tips: verify whether the drive expects the 3.3V rail before trying adapters; use an adapter that matches the rails your drive needs; if a drive won’t spin, check the power connector type, try a known-good SATA power cable from the PSU, and measure rails with a multimeter only if comfortable and careful. Refer to the drive/backplane documentation for any PWDIS or power-sequencing details.

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Member Avatar for finito

P1 3.3 V
P2 3.3 V
P3 3.3 V (precharge, 2nd mate)
P4 gnd (1st mate)
P5 gnd (2nd mate)
P6 gnd (2nd mate)
P7 5 V (precharge, 2nd mate)
P8 5 V
P9 5 V
P10 gnd (2nd mate)
P11 reserved
P12 gnd (1st mate)
P13 12 V (precharge, 2nd mate)
P14 12 V
P15 12 V

Member Avatar for firoz.raj

I Did not understand 3.3 V volt.why 3.3 V Volt is needed in the following case.Kindly
let me know the idea.Any help would be highly appreciated.

P2 3.3 V
Member Avatar for finito

From what I understand that Hard Drive and CD-ROM (DVD BD or w/e) require 3.3V. But Molex connectors provide 12v and 5v the two in between are grounds. I am not very sure how they work.

Edited by finito because: n/a
Member Avatar for firoz.raj

But Molex connectors provide 12v and 5v the two in between are grounds. I am not very sure how they work.

i did not understand molex connectors.the white which written p2 is a molex connector.kindly let me know some idea.additional why p2 is written there.

Member Avatar for finito

yes the white connector is called a Molex

Member Avatar for firoz.raj

Additional for DC Corrent distribution.why electric wire is in different color.red,yellow,black.why electric wire is in color ???Kindly let me know the
Idea.Any help would be highly appreciated.why it is different in color instead of same color.sorry for very small question .but i will ask.Kindly let me know the idea.

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