The most important difference with that module is that it's Registered, not that it's ECC.
Registered memory and unbuffered memory modules can't be mixed. Did you remove this module when you tested the others?

shamino wrote:

The most important difference with that module is that it's Registered, not that it's ECC.
Registered memory and unbuffered memory modules can't be mixed. Did you remove this module when you tested the others?

Yes. Thanks for identifyng the memory as registered, I'll see if I can find registered SDRAM somewhere.

have you tried a bios update?

candle_86 wrote:

have you tried a bios update?

Yes, that was the first thing I do after looking at the manual & the motherboard.

After you flashed the BIOS, did you completely clear the CMOS and load defaults? Occasionally there can be broken data in the CMOS RAM that makes the BIOS behave strangely. Sometimes that can happen as a result of changes in BIOS releases, but other times it's just some unexplained glitch that takes place and the broken values are "stuck" until it gets reset. There are settings that don't get shown to the user in the setup menu, but if they get messed up somehow they can break things.
Flashing the BIOS doesn't clear that stuff (it's not stored in the same place, I believe the CMOS RAM is in the southbridge).

What exactly are the symptoms when you try to use only unbuffered memory - is it powering on but no POST? Does it give a beep code?
The VIA 694T chipset is definitely compatible with unbuffered RAM so it ought to work. That's what the vast majority of people used on them.

If it won't run with only unbuffered memory installed, then perhaps the board could be marginally unstable. The use of registered memory might be stabilizing the memory bus just enough that it's able to run.
Are there any settings to force a slower FSB clock? If you force it to say 66MHz FSB and lazy RAM timings, and maybe even raise voltages slightly, does it start working with unbuffered memory?
Do the capacitors look good? I'm not real familiar with Chaintech but most manufacturers were using cheap caps back then.

If you have a multimeter, have you tried checking any voltages? Voltages shown in the BIOS are sometimes completely wrong so measuring with a meter is best. The PSU's 5v and 12v outputs can be easily checked at a molex connector, but other voltages are more difficult. The voltage at the RAM would be interesting but not as easy to measure. I can suggest a method if you want to try it.