*UPDATE*
I got the v1.6(b?) working. It looks as though it was a bios problem. The M8plus_16 bios would give the no audio/video on bootup, but then I tried the 'Yoshihiro-m8-1.6B-Memory-Fixe-Beta4' bios and it worked like a charm! So I dunno if there are still issues with some xboxes and the M8plus_16 bios - but it worked for me.
I ended up testing this pretty thoroughly - just to make sure. Here's what I did:
1) Started booting the xbox with the problem bios (which was a M8plus_16 bios that I had modified with EVTool 1.0.9). On the 8th boot I had no video. Pretty much every attempt after this resulted in the same thing (it would boot properly about 1 out of 5 tries).
2) Swapped AladdinXTs with one that had the 'Yoshihiro-m8-1.6B-Memory-Fixe-Beta4' bios on it. The xbox booted up 30 times without any problems.
3) To make sure that it wasn't a problem with the modchip that I had originally used, I swapped the SST chip from the working one (the chip with the Yoshihiro bios) and put it into the none-working XT. Booted the xbox another 30 times without any problems.
4) Just to confirm, I put the XT with the original, modified M8plus_16 bios back into the xbox and the problem showed up after only two boots.
5) Thinking that maybe it was a problem with the modified M8plus_16 bios, I decided to try a virgin M8plus_16 bios. I booted the xbox 27 times (which all booted fine), but then on the 28th boot, I started getting the no audio/video problem again (which would happen about 4 out of 5 tries after this). So even though the xbox booted fine 27 times with this bios, it still leads me to believe that the M8plus_16 bios isn't fully 'compatible' with this xbox.
6) Now, just to make sure (and be objective about this), I put the XT with the Yoshihiro bios back into the xbox and booted it another 40 times without any problems.
So after booting the xbox a total of 100 times with the Yoshihiro bios and not any problems, I think it's safe to say that this bios will work fine with this xbox.
I should also note a few specifics about the xbox and the install:
- v1.6 xbox (not sure if it's a 'b' version - I'll have to look into that to confirm it) with the brown power/eject leads
- 2004-09-09
- Dash: 1.00.5838.01
- Kernal: 1.00.5960.01
- AladdinXT installed alĂ 'always on' - LPC rebuilt, BT grounded & LFrame trace cut
I'm going to post this info in the 'Bios' forums as well - hopefully it may draw attention to this problem - as I don't think I'm the only person to come across this.