Old PSU

[Jeff Gaines]

As art of my clean up I have found a Corsair case with a PSU that has just
two cables coming out, one with the big (?24 pin) connector and the other
with two of the small square connectors.

Memory is struggling but is that from the days when we fed power just to
the motherboard and then plugged peripherals into the board? If so it's
probably for the bin?

[Andy Burns]

Post by Jeff Gaines
As art of my clean up I have found a Corsair case with a PSU that has
just two cables coming out, one with the big (?24 pin) connector and the
other with two of the small square connectors.

sounds like ATX12V P4 connector to the CPU(s)

Post by Jeff Gaines
Memory is struggling but is that from the days when we fed power just to
the motherboard and then plugged peripherals into the board? If so it's
probably for the bin?

Sure you've not "harvested" the cables with 3.3/5/12 volts to drives? Or
it's a modular PSU with cables removed?

There is a new(ish) standard called 12VO, where the PSU feeds 12 to the
motherboard, which then feeds lower voltage(s) to the peripherals.

[Daniel James]

Post by Andy Burns
There is a new(ish) standard called 12VO, where the PSU feeds 12 to the
motherboard, which then feeds lower voltage(s) to the peripherals.

Am I alone in thinking that's a pretty stupid "standard"?

Firstly, the motherboard has to provide the conversion to 5V and 3.3V
that would previously have been done by the PSU, so the cost of a board
will go up -- and you can bet that a 12VO PSU won't be significantly
cheaper than an ATX one so there'll be no saving thare. This means that
if the voltage-shifting functionality fails it will mean a new
motherboard (which will probably mean changing CPU, RAM, etc. unless the
board fails when it's new enough for a like-for-like replacement) not
just a new PSU.

Secondly, the motherboard will have to handle the current needed for
drives, etc., that are now fed directly from the PSU, which means
heavier tracks and possibly more heat generated on the board.

It also means that one has to worry about the current that a motherboard
is able to handle -- and the number of power output connections provided
-- if designing a system that is to have, say, an unusually large number
of drives.

I can't see any upside, for the user. I hope 12VO vanishes without trace!

[Theo]

Post by Daniel James

Post by Andy Burns
There is a new(ish) standard called 12VO, where the PSU feeds 12 to the
motherboard, which then feeds lower voltage(s) to the peripherals.

Dell, Lenovo and friends have long done that for their desktops.

Post by Daniel James
Am I alone in thinking that's a pretty stupid "standard"?
Firstly, the motherboard has to provide the conversion to 5V and 3.3V
that would previously have been done by the PSU, so the cost of a board
will go up -- and you can bet that a 12VO PSU won't be significantly
cheaper than an ATX one so there'll be no saving thare. This means that
if the voltage-shifting functionality fails it will mean a new
motherboard (which will probably mean changing CPU, RAM, etc. unless the
board fails when it's new enough for a like-for-like replacement) not
just a new PSU.
Secondly, the motherboard will have to handle the current needed for
drives, etc., that are now fed directly from the PSU, which means
heavier tracks and possibly more heat generated on the board.
It also means that one has to worry about the current that a motherboard
is able to handle -- and the number of power output connections provided
-- if designing a system that is to have, say, an unusually large number
of drives.
I can't see any upside, for the user. I hope 12VO vanishes without trace!

It's about having a lower cost system. Peripherals are increasingly onboard
these days - think M.2 SSDs where we once had SATA. As well as reducing in
number, the current demand of off-board loads is much lower (SSD v HDD).
The days when normal users would stuff half a dozen HDD, a DVD and a tape
drive in their office desktop are gone - that's what they use NASes, servers
and the cloud for these days.

Basically having a PSU pump out 5V at 20A and then use it for a single 2W
SSD is wasteful, so move that conversion to the mobo where you can size the
converters for the loads your system actually expects to have. That also
makes the conversion more efficient. Maybe you only need 10W so you have a
much smaller converter.

The remaining use case for high power systems is 'enthusiasts', who won't
buy an office PC from Dell anyway, or people with big GPUs. In which case
they need to swap out the in-box 200W PSU for a 600W monster anyway.

Servers have done this for decades: big iron might have a 2.4kW PSU that
only outputs 12V, and the rest is either on the mobo, backplanes or in a
separate converter board. That's enough to power their 4 CPU sockets and 24
drive bays or whatever they have.

Theo

[Daniel James]

Post by Theo

Post by Daniel James

Post by Andy Burns
There is a new(ish) standard called 12VO, where the PSU feeds 12
to the motherboard, which then feeds lower voltage(s) to the
peripherals.

Dell, Lenovo and friends have long done that for their desktops.

Really? It's been a while since I had occasion to poke around inside a
recent one of those.

Post by Theo

Post by Daniel James
I can't see any upside, for the user. I hope 12VO vanishes without trace!

It's about having a lower cost system.

Yes, lower cost to manufacture at the cost of versatility for the user.

I suppose I should applaud the potential saving in materials as these
designs don't have to cater for situations that usually won't arise, but
I hate this "vanilla-ization" of commodity systems.

Post by Theo
Peripherals are increasingly onboard these days - think M.2 SSDs
where we once had SATA.

I hate M.2. I like my drives in caddies so they can be swapped around
without opening the case, and M.2 doesn't allow for that. Well, you can
use M.2 disks in USB caddies, but that's a compromise. Might as well use
SATA.

Post by Theo
The days when normal users would stuff half a dozen HDD, a DVD and a
tape drive in their office desktop are gone - that's what they use
NASes, servers and the cloud for these days.

I don't think "normal" users ever stuffed half a dozen HDDs into a
desktop PC. The most I've ever had was two, and that was when disks were
a bit smaller than they are today and you needed more than one. As you
say that's a job for a NAS/Server.

Post by Theo
Basically having a PSU pump out 5V at 20A and then use it for a
single 2W SSD is wasteful, so move that conversion to the mobo where
you can size the converters for the loads your system actually
expects to have. That also makes the conversion more efficient.
Maybe you only need 10W so you have a much smaller converter.

Yes, I see that point ... but surely that's an argument for encouraging
people to pick a PSU that has the right power available at each voltage
-- and, indeed, an argument for not fitting a ridiculously
over-specified PSU, as so many people seem to do.

Putting the PSU functions on the mobo limits the usefulness of the whole
system, so the mobo (and probably everything else) needs to be replaced
just to increase the power availability.

I can see that for an off-the-shelf corporate PC that will be sold in a
particular configuration and only ever used in that configuration there
is no need for flexibility and the 12VO scheme may reduce manufacturing
costs ... but as soon as you start to talk about a system that may need
to be upgraded or used in different ways you're either looking at
replacing the mobo to get more power-handling or you're looking at
starting with an over-spec'd mobo that will be able to handle the
upgrades -- either of which will wipe out that initial costs saving.
Much cheaper to replace a PSU!

Post by Theo
The remaining use case for high power systems is 'enthusiasts', who
won't buy an office PC from Dell anyway, or people with big GPUs. In
which case they need to swap out the in-box 200W PSU for a 600W
monster anyway.

In this newsgroup its the enthusiasts I have in mind, of course.

I suppose what I'm really saying is that I hope the advent of 12VO and
the likes doesn't spell the end of normal ATX-type PSUs for those of us
that want them.

Post by Theo
Servers have done this for decades: big iron might have a 2.4kW PSU
that only outputs 12V, and the rest is either on the mobo, backplanes
or in a separate converter board.

I've no issue with server systems using the backplane or specialist
converter boards to manage the power -- that's sensible -- but also very
different from making the mobo do it!

[Andy Burns]

Post by Daniel James
I hate M.2. I like my drives in caddies so they can be swapped around
without opening the case

More what U.2 was designed for, than M.2 ...

[Jeff Gaines]

Post by Andy Burns

Post by Jeff Gaines
As art of my clean up I have found a Corsair case with a PSU that has
just two cables coming out, one with the big (?24 pin) connector and the
other with two of the small square connectors.

sounds like ATX12V P4 connector to the CPU(s)

Post by Jeff Gaines
Memory is struggling but is that from the days when we fed power just to
the motherboard and then plugged peripherals into the board? If so it's
probably for the bin?

Sure you've not "harvested" the cables with 3.3/5/12 volts to drives? Or
it's a modular PSU with cables removed?
There is a new(ish) standard called 12VO, where the PSU feeds 12 to the
motherboard, which then feeds lower voltage(s) to the peripherals.

Thanks for making me look again, you are right, I couldn't see the sockets
in the gloomy spare room without a torch!

Thanks again :-)