I need to power more hard drives, I have a free PCI-E cable

[usseN]

I need more power to run hard drives. I have a free PCI-E cable I think I can use to achieve this.

 

My first thought was PCI-E to Sata power convertion, but couldn't find any adapters.

 

I then started wondering if I can convert PCI-E to Molex and then Molex to Sata power. This is possible, but some PCI-E to Molex, and Molex to Sata power, have splits and multiple endings. This makes me worried about correct power consumption.

 

I want to run as many drives as possible. Anyone that can help me here?

[emosun]

pci-e is only 12v , you need a 5v line for a hdd as well

[Jurrunio]

if you have some molex cable around, that's better. Molex gives a 5V and a 12V wire while PCIe only gives 12V, while drives want both of these. 3.3V was used on old drives but new ones mostly don't.

[Cyracus]

The smart way to do it is get a power supply with more sata connectors

[usseN]

30 minutes ago, Jurrunio said:

if you have some molex cable around, that's better. Molex gives a 5V and a 12V wire while PCIe only gives 12V, while drives want both of these. 3.3V was used on old drives but new ones mostly don't.

So I can split the PCI-E into two Molex and then two Molex into two Sata, where both drives should have enough power.

[usseN]

30 minutes ago, Cyracus said:

The smart way to do it is get a power supply with more sata connectors

Haha, I agree, but that investment is a bit too much at this time.

[Jurrunio]

Just now, usseN said:

So I can split the PCI-E into two Molex and then two Molex into two Sata, where both drives should have enough power.

no you can't, unless you add a buck converter to convert 12V from the PCIe cable to 5V.

[Spotty]

What model PSU do you have?

How many SATA power connectors do you need?

[PianoPlayer88Key]

I'm in the same boat on my desktop.  I have the Corsair AX760 with 12 SATA power connectors, 4 per chain, 3 chains.  There's 5 SATA/PATA plugs on the PSU, so theoretically I could have 20 drives.

Even with that, it still wouldn't be enough to power

 

I would like to be able to run right up to the PSU's wattage limit with mostly hard drives.

If I had to, I'd downgrade from an 88W i7-4790K to a 13W Xeon E3-1220L v3 and 19W GT 710 (1220L lacks iGPU), and from 4x8GB G.Skill Ares 1.5V 1600/9 to 2x4GB Sniper Low Voltage 1.25V 1600/9 & run only 1 stick.

On top of that, I'd set my CPU to 1 core, no HT, BCLK 80 or 90 (whatever is the lowest allowed), multiplier 8, RAM to DDR3-800, CL 19, and undervolt everything to within an inch of stability (it wouldn't pass Prime95 but would still work for other things.  Cinebench might struggle a bit.)

I'd guess power consumption might be maybe 15-20W or so for board, CPU, RAM, but idk for sure.  But if I could run like 700 to 740 watts of HDDs with a 760W PSU...

 

Or, would just underclocking & undervolting my existing parts get the power consumption down to just as low a level?

 

One PSU I was considering more recently for maybe a NAS build was the HX750, with 16 SATA connectors.  Even so, I'd still run out.

[OrionFOTL]

28 minutes ago, PianoPlayer88Key said:

But if I could run like 700 to 740 watts of HDDs with a 760W PSU...

Look at the +5V rail capabilities of your PSU.

[PianoPlayer88Key]

1 hour ago, OrionFOTL said:

Look at the +5V rail capabilities of your PSU.

Top one is the current one, bottom one was pulled from my build that I did 11 years ago.

Was looking on newegg & pcpartpicker a bit, and most of what I saw maxed out at 30A on the 5V rail (or 150 watts).  I did see a couple 1500W units from Silverstone and one other I forgot that had a 40A 5V rating, as well as a VERY sketchy at best refurbished 520-watt  Vantec VAN-520A that has a 52A 5V rating (and a 28A / 336W 12V rail).  Even the 2000W Superflower or 1600W Corsair/EVGA units max out at 30 or 25 amps on 5V (125W or 150W).

 

As much of a percentage of PSU capability pro OCers use with their GPUs and CPUs, I'd like to be able to do the same with HDDs, so long as I limit the CPU & GPU power (like my proposed aggressive underclock & undervolt earlier).  Why can't we just mix and match whatever parts we want, so long as the total power doesn't exceed the "XYZ Watts" prominently advertised?  One person might want a lot of GPU, someone else might need a bunch of hard drives, maybe you could also charge laptops & tablets from a PSU, heck could there even be a niche situation of someone wanting to power a bunch of floppy drives, or charge their car battery, or run other household appliances?  (okay, powering the non-computer devices might be a wee bit of a stretch. )

[OrionFOTL]

29 minutes ago, PianoPlayer88Key said:

As much of a percentage of PSU capability pro OCers use with their GPUs and CPUs, I'd like to be able to do the same with HDDs, so long as I limit the CPU & GPU power (like my proposed aggressive underclock & undervolt earlier).  Why can't we just mix and match whatever parts we want, so long as the total power doesn't exceed the "XYZ Watts" prominently advertised?

Because the components inside the PSU that output 5V voltage are only capable of so much watts on that rail.

[PianoPlayer88Key]

25 minutes ago, OrionFOTL said:

Because the components inside the PSU that output 5V voltage are only capable of so much watts on that rail.

PepeHands.

 

I thought on many modern PSUs, the 5V rail was derived from the 12V rail?  Why couldn't a DC-DC unit be able to output whatever wattage it wanted on any rail derived from 12V (like 5V and 3.3V) so long as it didn't exceed the 12V rail's max rating?  FeelsBadMan (come on, where are those emotes when we need them, too lazy to look their images up and embed them Kappa)

[OrionFOTL]

1 minute ago, PianoPlayer88Key said:

I thought on many modern PSUs, the 5V rail was derived from the 12V rail?  Why couldn't a DC-DC unit be able to output whatever wattage it wanted on any rail derived from 12V (like 5V and 3.3V) so long as it didn't exceed the 12V rail's max rating?

Because the transistors on step-down DC-DC converters have their own current limits, just like the transistors that output 12V. Those 3.3V and 5V output transistors aren't as big as the 12V ones.

[PianoPlayer88Key]

10 minutes ago, OrionFOTL said:

Because the transistors on step-down DC-DC converters have their own current limits, just like the transistors that output 12V. Those 3.3V and 5V output transistors aren't as big as the 12V ones.

So how do servers, etc. get power for their hard drives when some of them have several dozen, or maybe a hundred drives?  I guess server PSUs are more geared for that sort of thing, or what?  (Also I'm wanting to figure out what type of chassis to house a bunch of drives in WITHOUT going rackmount, or getting a bunch of Drobos (which would by themselves exceed my entire non-storage portion of the budget for a project like that) or things like that.)

[OrionFOTL]

14 minutes ago, PianoPlayer88Key said:

So how do servers, etc. get power for their hard drives when some of them have several dozen, or maybe a hundred drives?  I guess server PSUs are more geared for that sort of thing, or what?

Hmm, I don't know. They need to have sufficient 5V capacity for sure, or perhaps the 5V is generated elsewhere (after all some server PSUs are 12V-only, 24V-only, or other voltage). HDDs use some 12V too of course.