So over the weekend I bought a Umax S900 with a sonnet G4 upgrade in it. The guy said it worked. I tried to boot it up and I got no chime on the S900 but I did get video out of the ATI card.

I then put a Sonnet G3 300 out of my 8500 in the S900 and it booted just fine. I put the G4 into the 8500 - same result - no chime.

I figure i need to check and see if either motherboard has any L2 cache installed on them and remove that as a troubleshooting measure, and maybe reset the CUDA switch. Anyone else have any ideas on how to get this G4 upgrade running again?

Is the Sonnet card one with a soldered-in CPU or with a ZIF CPU? Probably the former, from my experience, but Sonnet did produce ZIF cards with either IBM or Motorola 7400s, and probably other G4s. It was Sonnet's boast that no jumpering, and no CP, was required, which seems largely to have been true, but part of that convenience may stem from Sonnet's extension. Do you have the latest, pre-installed (before installation of the G4)? There is a sonnet_firmware_updater_v31.pkg.zip, and a ce_install_v31.sit, available from Sonnet's site.

There are other desirable wrinkles, such as use of the CUDA switch to cue the system to the presence of a radically different CPU. Did you? It is my understanding that the clones were mostly based on the Tsunami architecture, which, as in the Nitro in your 8500, have no removable cache. The NewerTech G3 upgrades have, in their CP, the facility to ignore the existing cache, but I suspect that the Sonnet extension simply disables it, because the supplied L2 with Sonnet cards is usually much more generous (0.5 or 1.0MB).

de
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(60x) 13DT + 3PB + PTPro; (G3) 7DT/MT; (G4) 3T + PB. System 8.1 to OS 10.5.8

a bit late maybe but its some ROM issue that prevents the mac from chiming on poweron with a sonnet G4 card installed. so it should be normal that it wont chime.