Well, no, the only difference between a 20 pin and a 24 pin plug is an extra 4 pins for +12V, +5V, +3.3V and ground. Since the pins on an ATX molex are rated for about 6-10Amps, a motherboard that draws >18A will melt the plug. So they give a second set of pins to split the current across.
Thus a small power supply has no need for 24 pins, because there will never be more than a max of 10A drawn.
A machine not booting is due to not enough power provided, not due to a discrepancy between a 20- and 24-pin molex.
See for yourself:
http://www.formfactors.org/developer/sp ... ic_br2.pdf
This section briefly summarizes the major changes made to this document that now defines ATX12V power supply. With the move to 12V voltage regulators for the processor, ATX guidelines for 5V as main power are no longer provided.
1.2.1. Increased +12 VDC output capability
System components that use 12V are continuing to increase in power. In cases where expected current requirements is greater than 18A a second 12 V rail should be made available. ATX12V power supplies should be designed to accommodate these increased +12 VDC currents.
1.2.2. Minimum Efficiency
Minimum measured efficiency is required to be 70% at full and 72% at typical (~50%) load and 65% at light (~20%) load. The recommended guidance is 77% at full load, 80% at typical (50%) load and 75% at light (20%) load to provide direction for future requirements.
1.2.2. Main Power Connector:
The 2 x 10 main power connector has been replaced by a 2 x 12 connector. This was made to support 75 watt PCI Express*requirements. Pinout assignments are based on the SSI recommendation.
With the added 12V, 5V, and 3.3V pins the need for an Aux Power connector is no longer needed and the guidance for this connector has been removed.
1.2.3. Separate current limit for 12V2 on the 2x2 connector:
The 12V rail on the 2 x 2 power connector should be a separate current limited output to meet the requirements of UL and EN 60950.
at this point the only reason to go with a PW and not a pico module is if you're not confident in the regulation of your outboard voltage supply. the y2515 has solid regulation on the 12v, and the pico has higher compatibility
I'm not sure if I understand. The PicoPSU provides 90 or 120 Watts maximum. The PW200 provides 200W maximum. Is that not a big difference?