Solved Some Haswell info

[Britton30]

I sent an inquiry to Jeffery of ASUS support about some comments he made in Newegg's review section. I expressed concern about why so many ASUS Z87 boards were being returned as DOA. Here is his interesting explanation.
Please add your thoughts or knowledge.

Hello Gary,

Looks like when the new Haswell board released their are some PSU that are not compatible with the board that won't allow the board to turn on. Haswell has a low voltage to turn on and these PSU are assuming the board isn't getting enough power which customers assume its DOA.

When you purchase the Z87 board, you have the best contact to get things done in a timely manner and worry free as much as possible.

Regards,
Jeffrey

 

[Layback Bear]

I have no idea what that means.
Gary can you put that in Ohio English?

 

[Brink]

That sounds correct. Intel's Haswell processors feature a new sleep state that isn't compatible with all power supplies (PSU).

Here's an interesting article about this.

The big Haswell PSU compatibility list - The Tech Report - Page 1

 

[Britton30]

I have no idea what that means.
Gary can you put that in Ohio English?

I'm writing from memory, but I think it means this: Even when a PC if "off" the PSU still is supplying a stand by voltage if it is plugged into the wall. When you hit the PC power switch the PSU responds with a quick voltage check of the board, maybe 200-300ms in lenth. IF the PSU detects a lower voltage than expected it won't "turn on" and there is no start up.
As example only, say an older board draws 5V at start up and the Haswell board only draw, say, 0.8V the PSU will take that as a failure to start. Those figures are just guesses for illustration.

I'm not sure if failing to wake from sleep is the same as failure to post, but sure seems related to Haswell's lower power needs.

 

[kbrady1979]

This was a known issue before Z87 boards and Haswell CPU's were even launched. There was a list of known good PSU's out as well. There will probably be a fix for this soon if it is a big problem. Intel isn't too big to make mistakes, but they usually clear them up in short order. Thanks for sharing this Gary.

 

[Layback Bear]

Thank you all. Now I understand,

 

[Britton30]

You're welcome Jack. Don't feel bad, I don't understand half of what I know, hence my avatar.