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I do know, but it is a 1:1 replica of the original module using the same hard to source components and precision resistors... not to undermine the immense effort of the task, it seems the hybrid just generate +5V and -5V, as well as a couple control signal for the PMU.

The hybrid module pretty much deal will all the voltage rail generation on the motherboard, with power sources coming from both the power adapter, and the battery. It uses some external components, a couple MOSFETs that are around it, and a LT1070 to generate the +12V rail. 1989 vintage DC/DC...

I have to look at the schematics in more details but I don't think it does.

Big question, as I currently have a Macintosh Portable from a friend that is suffering from a bad hybrid (it has taken a toll of some chips in the audio section, and the 5V rail is looking absolutely horrible with spikes up to VBAT). It seems the hybrid does not do much, other than generating...

Well it was a good plan to add the DIP switches then! Did not thought of the impossibility to use software PLL settings in specific cases.

Oh no way! I'll check that! All the vias are tented under the BGA and under the PGA, otherwise. Edit: I checked that little solder blob and it did not make connection to anything, took it off.

It does, I did put 256MB in mine. It's absolutely useless and makes it very slow to boot, but it works! :D

I honestly though no one would try because the board is exceedingly rare, and also it's a very difficult project. It took me two full month to sand down the PCB and retrace it all, and make verifications. Getting the 8 layer PCB manufactured also took a long time. Ultimately there was the...

I'm afraid I have missed the thread, but I have already made a replica of the PowerLogix 750GL accelerator... It however does not work as I did blow the VRM, so there's possibly a short somewhere in my design that I need to trace. I had a PowerLogix board that I recovered from a scrap lot, that...

I'll probably make a bunch of 16MB SIMMs as well, which would be more economical if you want 64MB.

I have ordered the chips, but shipping is usually super slow. Hopefully within 6 weeks I will have them to make 4MB sticks!

Unfortunately I do not know further easy ways to debug. Having a logic analyser to look at the bus activity during boot would greatly help I'd guess, to see if the CPU does something, and where it would hang. But I have no idea about the boot sequence, this would have to be reverse engineered...

VRAM will not prevent the board from not chiming/booting if corrupted or absent.

It's not because they have been sanded and laser remarked that they will not work, it's just that you don't know what you get at all and the markings are not original. They are remarked from whatever stock, speed grade and mask they have, to make a product that looks new and a new stock that is...

The 1993 date code on the 33MHz one matches, but who knows what you'll get... The 2012 date code on the 40MHz was when Motorola long became Freescale, 100% fake. Photos can be for indication purpose only, very common on ebay.

Pretty much all 40MHz 68882 will be fake. I don't think Motorola made them in PLCC package (33MHz was the highest). If it's laser engraved it is very likely fake as most of the production was made with silkscreen printing.

Look at the mask revision, the smaller the lithography the less heat/faster you can get. D66C is 1.0µm so they should fare well with overclocking.

I have two 840av motherboard that do not chime, and it is something that seems common. There's likely a common point of failure for these and hopefully someone can figure it out, but it will probably require some significant time and test equipment (maybe a logic analyser) to see what the CPU is...

It's a matter of bandwidth more than capacity. If you have 512kB but only have the bandwidth to read 256k in the period you refresh the screen, your extra 256k is useless. Recent Quadra are using many 256k SIMMs in parallel to increase the bandwidth and access the higher resolution/color modes...