[coreboot] Will a KCMA-D8 boot without the 8pin EPSV12 cable if you are using a 35W CPU?

Taiidan at gmx.com Taiidan at gmx.com
Sat Nov 17 03:14:46 CET 2018

On 10/19/2018 05:15 AM, Nico Huber wrote:
> On 10/18/18 3:16 PM, Angel Pons wrote:

Thanks for replying all!

>> I believe the power traces are different, so the CPU VRM feeds only through
>> the EPS12V connector. However, if your PicoPSU is large enough, I guess a
>> EPS12V cable can be attached to it.
> Probably not for a 35W CPU

In comparison I have various other boards with higher wattage CPU's that
lack EPS connectors such as an AM1 for a 40W CPU...what is different? I
mean the 8pin one not the 4pin cpu cable.

> but generally: Using adapters for the
> EPS12V connector is dangerous. 

I know - I am the one who added that on the wiki :D but it is always
good to repeat it :D

> They have more than two pins for a
> simple reason: The electrical current through each pin/connection must
> not get too high. There are adapters that route the whole current
> through a single pin on the other end (e.g. a single old-school PATA
> drive connector).

Oh man that is bad

I wanted to either not connect a 8pin cable at all since a very similar
platform on the AM1 series doesn't need or come with one or use one of
my adapters that combines a 4PIN CPU cable and a molex cable which has
worked fine on my H8SCM with the same CPU before I got a new PSU for it
(H8SCM only $40 - I don't want to risk this $300 brand new KCMA-D8
although they are going for only $90 china used on fleabay atm)

> Never use these unless you know they can take the
> current you expect! (e.g. not much more than 3A for a 35W TDP, that
> might be ok for a single pin, but you should read each connectors
> specs)
> Same applies to the tiny connectors for (hard)-drives on the PicoPSU,
> if the current goes through less pins on the PicoPSU side, don't do it
> (unless you know what you are doing).

I always check the ratings.

> There are PicoPSUs that have a 4-pin EPS12V connector btw. 

I know I have one :D

But dont I still need 8 pins total?

> So I'm not
> sure what the original question was; would it work w/o full 8 pins? 

I just want to make it work with a normal CPU 4pin cable

> or
> would it work w/o any? The former likely yes, the latter likely no.
> Nico

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