Re: Computer turns on and then just dies

On Thu, 11/28/2024 8:34 PM, VanguardLH wrote:

> 
> Some PSUs still have cabling for floppy drives.  There are adapters to
> change to sata power.  Are those safe to use for sata power?
> 

There might be one of those floppy connectors on the supply.
Maybe a supply older than my collection, had one of those on the end of both looms.

http://www.playtool.com/pages/psuconnectors/connectors.html

  "The four pin floppy drive cable showed up
   when PCs started including 3.5 inch floppy drives."

   Socket housing   Socket          Maximum current per circuit
   AMP 171822-4     AMP 170262-1    3 amps

That means you could draw 3 amps from +12V and 3 amps from +5V.
At a stretch, that's two hard drives off one "adapter",
assuming you can find a "floppy connector to two SATA 15p"
adapter. It is basically the same situation, as a SATA to two SATA
adapter.

At one time, the power footprint of a hard drive was close to 40W.
(That's also why the sleds had three fans blowing across the surface.)
Drawing 3 amps from +12V was a real possibility. Today, the small capacity
boot drives, the manufacturer wants those to spin up in five seconds,
so the current will be closer to 2 amps on +12V. For the
higher capacity drives, with more platters, more mass, they
turn the max current down, and make use of a 20-25 second
startup before those are ready. Some of the BIOS are set
to time out after 35 seconds, which gives some idea how
much faster than necessary the boot drive is at 5 seconds.

I haven't timed my single sample 18TB drive, but after it spins up,
it still does not ID itself, and it insists on rattling the
heads and doing self test, before it'll talk to anyone.

*******

They spin up forty five identical 4TB Seagate drives at once and it draws 50 amps
on the +12V rail. That works out to a bit more than 1 amp of spinup current.
That's not considered a boot drive, which is why the current is that low
at start. This measurement is not being done with staggered spin enabled
in the pod.

https://www.45drives.com/blog/storage/the-power-behind-large-data-storage/

I measured two small boot drives:

WD5003AZEX  1.64A startup current on +12V (yellow)
WD1003FZEX  1.65A startup current on +12V (yellow)

The interval at full current was so short, I missed detecting
the peak on the second drive. And needed a second power up sequence
to catch it. The time spent at 1.65A might be a second or so.
with some preamble/postamble on either side of that.

Both of those drives are 1 platter. In fact, at the end of life
of the WD5003, they were making then with 1TB platters and
throwing away half the capacity, in order to make drives. Of
three of that model I bought, one was short stroked. The heads only
go from the outer diameter of the 1TB single platter, to the middle of the
single platter. Which is cool and all.

It's possible an older drive, has a bit higher current.

Even if two drives off one source exceeds the current by a bit,
the duration of a second or so at that level, isn't going to hurt anything.
It's not a thermally significant interval.

   Paul