what voltage and ampage is the AT board?
what are you trying to do?
make it simple for us and we can help more
Basically I am trying to upgrade a certain system. The system has an old motherboard which doesn't need the 3.3 V rail or simply it has regulators to generate it. I need to replace this motherboard with an advanced one (which I already bought "http://www.ibase.com.tw/2009/MB970.html". The thing is that the old AT-power source now can't be used to run this motherboard, at the same time I need the AT-power board as it has other functions (so I can't get rid of it).
I need a way to connect this AT power board with this motherboard in a way that I take the lowest possible power of it (the AT-power board). So how can I combine the AT power supply board with the ATX PSU on the same motherboard??.
The following pictures of the power plug you see connected on the motherboard is for the old motherboard which I believe is customized (the motherboard) to work on AT-power (has inside regulators), so I can't use it with my new motherboard.
http://cdn.instructables.com/F2H/37I7/I1MQ5YDL/F2H37I7I1MQ5YDL.LARGE.jpg
http://www.instructables.com/files/orig/F6P/UV9E/I1MQ5YES/F6PUV9EI1MQ5YES.jpg
Some guys suggesting me only to wire the grounds of both PSU's?- okay.
Which PSU should I connect to the 20-pin ATX power connector??, also
which PSU is going to supply the harddisk, and DVD?.
Can I connect +12 V, and +5 V rails form the AT power supply to the ATX connector (as the power good signal is fed from them to the relays), while sharing its 4-COM's with the other ATX PSU on the same 20-pin connector. And filling all the other pins on the 20-pin connector from the ATX PSU??.
http://www.instructables.com/files/orig/F3G/7V66/I1MQ5YCE/F3G7V66I1MQ5YCE.jpg
For operating the motherboard with the AT-power board at the same time I only need to make a jumper to connect the PS_ON, along with one of the COM's on the ATX connector to the ON/OFF switch that starts the AT-power supply itself. Is that correct??.