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Are you able to export PRAM config on your 475 with memory test disabled and memory test enabled? Those might be different.

A button to disable memory test does not appear when opening Memory control panel with Option and Control key pressed under System 7.5.5. Are you running 8.1? Is change persistent, when starting with another OS version?

First have two capacitors in a row. Lets say 1µF each. So you can measure 0.5µF for both. Next detach C Meter as it will disturb charging. Then charge 1 capacitor to 5V. Second capacitor uncharged. When removing battery, capacitor stay charged. Then charge the other capacitor with reversed...

If using MLCC that are 5x - 10x in voltage, DC derating should not be an issue. 1uF 50V in 5V environment should be fine (if not faked).

You do not hijack, as it seems this more about capacitors in general than Ceramics only now. I do not have any clue about Polymer Tantalum but I noticed both of them are 7,3mm in lenght instead of 6,3mm the original capacitors were. Might work but is a little tight.

I did some tests: - My meter is not able to measure a charged capacitor. Always discharge while measuring. - If I put 2 capacitors in a row, I can charge them with opposite voltages so the overall voltage is 0V and the capacitance is halved. - Starting with the 22µF 50V ceramic I ordered from...

At least they do not blow up or short circuit or change capacitance at 46V within half an hour (That is was what I tested with my lab power supply). I assume they are not 50V but I would be fine with half of that as well. I know about DC de-rating but this is depending on the max Voltage...

Using - 68040RC40 - MC88916DW80 and moved SCSI resistor - 1MB 60ns VRAM - 128MB 60ns RAM - Heatsink I am able to run stable at 50MHz. At 53MHz I get video glitches and at 54MHz the system crashes. Are there 64pin 50ns VRAM for LC475 existing? I know for Powermacs with 112pin they are. Also I...

In between 2 boards are recaped with ceramics. Those capacitors are not as important as expected. My LC475 board run at 40MHz even without ALL 47µF and 100µF (except those at the audio chip) stable. The board run with 70µF Ceramics instead of 47µF fine as well. I ordered 100µF 50V ceramics...

As there is already a fan nearby, I solved it like this: Most of the airflow is forced to go thru the CPU heat sink. This keeps CPU quite cool, even at 40Mhz.

Some pictures about changing MC89920. Yes there is to much flux under the chip. I forgot to thake a photo with battery and speaker connector back in place.

You are right, "...It will always try to output the input frequency times 2...". I did some measurements: Yellow line is input of MC88920 pin 8, blue line is one of the outputs pin 10. MC88920 TRY to output double of input. This work well for Input 12,2MHz -> Output 25MHz (25MHz.png) Input...

Replacing the part is advanced soldering, as is is SMD and some temprature sensitive parts near by: SCSI plug, PRAM battery, processor socket, speaker connector. What I did was: - De-solder PRAM battery holder and speaker connector - Build a heat shield for SCSI and processor from old PCBs -...

I found two kind of sources for MC88916DW16: - E-Bay (there are many similar offers like the one Joopmac linked. - Aliexpress Both are from China and both are questionable. I ordered one part from one of the E-Bay suppliers and one from Aliexpress. Part from Aliexpress look new and work fine...

I propose to split the MC88916 topic to this thread https://68kmla.org/bb/index.php?threads/upgrade-mc88920-to-mc88916-for-lc475-p475-q605-advanced-soldering.48616/

In the Overclock LC475/P475/Q605 without soldering or spicy-o-clock thread I learned that LC475 can be pushed to the limit of the MC88920 by software, but to exceed this limit MC88920 need to be replaced by MC88916. There were some questions about availability and sources that can be discussed here.

A bug was found in Phiplis extension 0.1.1 that change every frequency setting except of 20,25,33, and 40MHz to maximum frequency of MC88920. (first digits of M parameter were set to 0) Bug was identified and Phipli build an update of the extension version 0.5.1 that fix the bug. Source code is...