Re: A marginal problem

Norm Why wrote:
> Hi,
> 
> 1) My PSU is 400 Watts.
> 
> 2) The latest hardware additions have marginal problems. I.e. SEDNA - PCI 
> Express mSATA III (6G) SSD Adapter with 1 SATA III Port. A) The mSATA III 
> (6G) SSD is 100% reliable. B) SATA III Port connected to a new SSD is 100% 
> unreliable.
> 
> Questions:   1) Could the unreliability be connected to something other than 
> PSU?
>                     2) Would a 500W PSU solve the problem, or
>                     3) Would 600W be a better idea? 

A hard drive draws 5W to 12W or so, just a ballpark figure.

A SATA SSD draws 3.5W from the 5V rail.

The SATA controller card, you would allocate 1W for the main chip.

When a controller card has no heatsink on the main chip, the
main chip is then power constrained and no more than 1 watt or
2 watts could be dissipated at a decent range of room temps.

*******

There's nothing wrong with suspecting the 400W supply has a
defect and must be replaced with another 400W supply. But
not a lot is to be gained from bumping the power, since
that just gives more 12V current capability.

Let's draw some pretend Seasonic-brand PSUs...

   3.3V @ 20A  \____ no more than 100W combined \
    5V  @ 20A  /                                 \___ 460W total max
   12V  @ 30A        360W                        /

   3.3V @ 20A  \____ no more than 100W combined \
    5V  @ 20A  /                                 \___ 580W total max
   12V  @ 40A        480W                        /

   3.3V @ 20A  \____ no more than 100W combined \
    5V  @ 20A  /                                 \___ 700W total max
   12V  @ 50A        600W                        /

Every Newegg advert for a PSU, shows a picture of the
supply label on the side, so you can plot these trends
for your own self.

The 12V powers a hard drive motor, at maybe 12V @ 0.8A idle spin current.

But we're not particularly gaining on the lower rails,
because the Seasonics are pretty well all double-conversion
and use a separate power board for the 3.3V/5V combined supply.
Any supply with "80+ efficiency" labeling, is double forward
conversion.

Even if I bought a 1200W modern supply, it would not
offer enough low-rails power to run my old AthlonXP processor
and NForce2 chipset. If you need to buy a PSU for an
antique computer, it's harder to get what you need to
finish the project.

    Paul