[weblacky]

Well, that’s why I asked about the CPUs’ operation otherwise. If you remember my PIMM repair thread from oh so many years ago, with a 600Mhz Fuel PIMM from user “noguri” I found that both the VRM was genuinely damaged and it had taken the PIMM’s ENV chip with it.

https://forums.irixnet.org/thread-3238.html

I ended up repairing both, and as you yourself suggested on that thread because the VRM had some out of small damage, causing it to operate improperly, and it was experiencing higher voltage on the 5V line, which is what actually damaged the sensor to begin with, in my case the reading was actually higher than the actual voltage and the ENV chip was no longer able to actually report the correct voltage but was still alive. It was both a matter of VRM damage and incorrect reporting but present CPU. So that’s why I asked if his other values are still there. It’s possible he could have some voltage values appear OK or at least within known range but his temperature has gone bad.

I’ve not heard of the CPU not being detected at all. However, I guess it depends if the i2c is used for that and as you yourself know if the ENV chip collapses in a certain way, it can definitely hold down that bus so that no one else can communicate, but normally you get a bunch of “node not acknowledged” errors in your L1 as an obvious sign of this collapse.

I’ve only done this once so I have no other situations to draw from. But I know for this user the system was booting normally and he already had a third-party ATX power supply using Kuba’s power adapter so I really doubt his power system went weird and took out some thing. Although given the age certainly anything is possible.

It’s the same exact chip that’s on the fuel main board for sensing, DS1780. However, I am not 100% if the i2c bus is the sole domain of the environmental monitoring system or if it is also used for other purposes.

In the case of you saying your CPU isn’t even detected the only thing that I understand that could come to mean is either the identification information is not available, and this could be due to either the eprom chip being damaged or much more likely having some sort of voltage failure on the board itself that might cause very wrong PIMM voltages or something of that nature. Either too high or too low is going to affect the CPU or components. So I would assume a problem with that voltage would yield us the mysteriously empty information. Either permanent damage or a protection circuit or not enough voltage to run the components. Remember that voltage right outside the highest value on the DS1780 legs does damage to the chip. But to do damage to the entire PIMM chip is a slightly different matter that I would need more samples to research further.

I guess to put it another way does it say you have no CPU because there’s not the correct voltage, or there’s not the correct identification, or is it because the CPU hardware is damaged and basically not there anymore.

Thanks.