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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...

It really does not matter ultimately. Ceramic is usually the preferred choice for high performance applications because they are solid state, long life, and have a very low ESR and ESL. Tantalum and electrolytics are polarised because of their construction, it is a limitation more than it is a...

Go for it!

Ceramic capacitor have a lot of advantage since they are entirely solid, they tend to cost quite a bit more than tantalum and electrolytics, especially when you start to go above 10µF. One trick that I use often is to parallel them (10+10 = 20, close enough to 22µF), which helps you buying less...

Markings are genuine, they look good

On my HP DDS DAT the plastic of the spindles has split and they pop out since there's a spring under them.

A celebration of the 68040 with one of my favourite chip from my collection

Actually it's the opposite of oddball because it's a JEDEC standard. 5V DIMM were relatively short lived, not widespread in PCs, and quickly eclipsed by SDRAM, so today they are not common, especially the server variety with parity.

Here's a quick note with the module bus width. Provision for double parity exist in the JEDEC standard and is mostly used by IBM, they are rare but they do exist. Any modules that will have a different number than 2, 4, 8 16, 32 memory chips on them will have a good chance to have parity...

The 85C30 is a dual interface chip. The best way to do it is to grab some samples from different sources and see what you get before ordering a larger quantity (should you need more). I can't think of any use of the 85C80 outside of macs, but it should still be a standard part from the AMD catalog.

I have decaped the 85C80 and you can clearly see some small logic of the 53C80 and the two SCC 85C30 on the die :)