Tyan Tiger MP (2460) won't post with two processors

[Rave]

Right. Got a Tiger MP here that I'm trying to get going with a couple of modded Thoroughbred XPs. It'll post with each chip individually, but both together is a no go. I pinmodded the slower of the two chips to give it the same multi as the faster one, again no go. I've dropped the FSB to 100MHz using the jumpers. I've tried a different power supply. I've redone both L5 mods- although I wouldn't expect a failed mod to cause a non-post in any case, it should just use one processor surely?

Any ideas?

[Agent]

What PSU do you have ?
Generaly accepted figures of PSU requirements for Tyan boards are atleast 30 amps on the +5 line, and preferably above 20 amps on the +12 line, probably worth checking.
Btw, you might want to read this

[Rave]

The two PSUs I used were pretty feeble it is true. However, they're Tbreds (Edit: originally put Tbirds) at 1266MHz, whereas the board is rated for two Pallys at 1.6GHz, so lack of current shouldn't be a problem I would have thought.

However, the two processors have different voltages, one is 1.5V and the other is 1.6V. Would that cause it to fail to post?

Edit: Shoved my multimeter into a molex and it showed the 5V line at 5.05V whereas I would expect it to sag if it was being overloaded. What I didn't realise before is that it'll post with one processor in either socket, so I now also know for a fact my pinmod is correct and the processors are set for the same speed.

Edit: also it's on the V1.03 bios; I'll try updating it to the latest one if I can't get it sorted tomorrow.

[Agent]

However, the two processors have different voltages, one is 1.5V and the other is 1.6V. Would that cause it to fail to post?

Really have no idea, i wouldnt have thought so though.
I had exactly this problem on a Tyan mobo too, although not the same model, and it was the PSU (was being run off a 380 watt Antec but was having non of it, so not a el-cheapo one).
Measure the voltage reading off the ATX header on the mobo (turn it over / angle it if you can), or follow the tracks on the mobo to the first component it hits, and take it off that. You can also try touching the pins from the top of the ATX header if you wiggle the wires around a bit, just be carefull not to short anything (unlikely, but just take your time )
Other than that, i dont know what to suggest other than the BIOS you already mentioned. I only have limited experience with dualies.

[Rave]

Other than that, i dont know what to suggest other than the BIOS you already mentioned. I only have limited experience with dualies.

Yeah me too, this is my first (I once bought a knackered BP6 as a project but couldn't get it going at all ).

I might have to join the 2CPU forums to see if they know what's going on.