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I got it: XC is not a guaranteed fail - that was mere speculation. Still don't know the difference between XC and MC, or why they changed over, but I'm no longer concerned with that at this point. I'm concerned about fixing the issue of the bus walk and the strange results. I found something...

Am I still overthinking this, or is there another answer as to why my particular CPU is not 'walking the bus'?

CayMac Vintage on Youtube has experienced a bad XC CPU, in a video of his about 7 months ago. Every board in this unit has been recapped. I included a link to a thread showing everything that's been done to it, above. The CPU is not walking the bus, I have a scope and am looking at every...

I should have the new MC68030RC33B CPU shortly, I'll follow up when it arrives. If in fact my XC is bad, what would have killed it? Why would Apple switch to the MC68030RC16B, if the XC was good enough? What's the actual difference? Summary of troubleshooting and current issues with my SE/30...

Thanks for the reply. On ebay there are a few loose SE/30 boards for sale, from 1987-1988, early SE/30's like mine, where the boards look new still but they all have the simasima pattern and they all have the XC68030RC16B CPU's. I am wondering if the XC, like you said, was an early chip that...

Thank you so much!

Can I use a Motorola MC68030RC33B in an SE/30? https://www.ebay.com/itm/371776928912. The CPU my SE/30 came with was a XC68030RC16B, which seems to be very rare and I can't find an exact replacement.

Going to have to try ordering another CPU, want to replace it with the same I already have.

Tried the CPU walk the bus test and I can't get a square wave from any of the ROM slots, the wave form is a mess, with varying speeds, nothing is consistent. Is there any way to tell if a CPU is bad without another one to test with?

I was measuring RP7 pin7, not Pin2, Pin2 goes to 0V with Reset, RP7 is working correctly, my mistake. Added sockets for UB10 and 11, the Sony Sound chips, cleaned the board underneath thoroughly. I can get Pin5 on both UB10 and 11 to go to 0V with the Reset button, but Pin6 only drops to...

I did setup my scope better, I guess I won't worry about the slightly slower speeds 3.67MHz vs. 3.9 Mhz, all the clocks are where they're supposed to be. I moved on to the Reset portion of the guide and I definitely have a problem here: UB11 pin6 only drops to about 4V with the Reset. RP7...

Went through the clock signals and not sure what to make of this. The C16G clock running the same speeds as C16M seems odd since all of the C16M clocks were exact. The E clock is off too. But the strangest is the C3M clock wave form, when compared to the others, this is C3M running slightly...

UE10 was confirmed to have 5V at pin 35 and the Reset is working also, UE10 appears to be in good order. Will check the clocks tomorrow.

Got confused by the pin count, all the UE10 pins are now connected correctly and not missing anywhere. Still Simasima and no sound. Will keep going tomorrow.

After going through the Simasima Repair Guide from TD.com, it is recommended to start with UE10 ASC sound chip, as everything crucial to boot passes through there. Printed out the Address and Data line matrix and went through all of the UE10 pins, back to the ROM slot. On the very last pin to...

Thanks for the encouragement! I'm determined to get this going one way or the other :)

Should've looked before asking, that video must be referencing the 128-512K models. Thanks!

Alright back at this. I have a Reloaded V5 Purple board that is due to arrive tomorrow, thanks to @schrockwell, but I'm going to give my stock board every last chance to work before scrapping it. Still no chime, just an audio pop on boot and static through the speaker or external audio jack...

Thanks for clarification. I ordered (2) sets of the PLCC20 sockets just in case something goes wrong. Also appreciate the BOM from Digi and Mouser.

@schrockwell, regarding the PLCC20 sockets: ebay shows these as $1.80 for (3). How did you end up spending $13 on these - according to your inventory list above - if the shipping is $5.25 and the (3) sockets for UD12, UE12, UH7, are only $1.80? How many of these PLCC20 sockets did you end up...