ACPI S3 not working. Could PSU be to blame?

[joefriday]

Hello. I've got a problem with my current rig. Here are the specs:


Dell Dimension 4500 case
Dell 250 watt PSU
Asrock 775i65G mobo
2x256MB pc2100 DDR ram
Pentium D 805 undervolted @ 1.15vcore
GeForce3 Ti200
Winfast TV2000 XP Expert
Aureal Vortex 2
Seagate Barracuda IV 80GB PATA
Seagate Barracuda 7200.7 200GB PATA
Windows MCE 2005


No matter what I do, I cannot get it to go into S3 standby. The motherboard's bios has the option for Suspend to Ram, as either being OFF or AUTO. I set that to auto, and used Dumppo.exe to check my min sleep state, which was set to S1, I modified it to set min sleep to S3, rebooted, and the setting held. However, even with those changes, the computer still will not go into S3. I thought perhaps the pci capture card or audio card were preventing S3 from working, so I uninstalled their drivers and removed all the PCI cards. Still no S3. I then uninstalled the AGP card and driver and switched to IGP. Nope, didn't help. So at this point all I had in the system was 1 stick of ram and the CPU. I couldn't get anymore basic than that. I then thought that perhaps my problem had something to do with the OS being MCE 2005, or my installed programs, or that the OS was originally installed with the Suspend to Ram bios option set to OFF, so I did a reinstall of Windows XP pre-SP1 and installed only the necessary drivers to set up the system and no other software (still using only IGP, 1 stick ram, no pci cards). I made sure the bios had Suspend to Ram option set to AUTO before the installation of the OS. Even after all this, it still could not enter S3 sleep state. I used dumppo.exe to check the min sleep state, and (I believe, not sure anymore) it was indeed set to S3, but it still wouldn't actually enter S3 when going to standby. This leads me to believe that it's either the motherboard, or the PSU that is the problem. The motherboard, as shown in the bios, obviously is SUPPOSED to support S3, but unless I hear form other owners of the same board, I don't know how well it actually works. The power supply itself is an older unit from 2002 which is the original Dell OEM power supply for the Dimension 4500. From what I can remember, even in the original OEM configuration, the Dimension 4500 never did enter S3 standby, always only S1, but I cannot guarantee the original Dell mobo wasn't to blame for that. So, is the PSU needed to be ACPI compliant to enter S3 standby? If so, how can I tell before buying if a new PSU will work for S3 mode? Also, does anyone here own the Asrock 775i65G motherboard that has functional S3 support?

Thanks

Joe