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jessenator

68882 FPU p/n & mask

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Ok, Since I kinda answered most of my questions with chipping, I figured I'd ask a specific question and actually put it in the correct forum :) 

I'm planning on getting a PDS riser for my IIsi with an empty FPU socket. Which specific P/N do I need?

According to this database, there are several revisions and masks— now, I'm a noob and I haven't look up what a processor's "mask" would be, I just have enough presence of mind to ask those who do know. :) 

The Apple NuBus riser card has a MC68882FN20A FPU with a mask of 1C12R. So does the Daystar PDS riser. Can't find a googlesearch image of the Supermac one with an FPU housed. These packages with numbers matching are presumably still available from Herb's Mac Stuff site. (I haven't asked him about those, specifically)

On ebay are several MC68882FN20A FPUs but the mask differs: 2C12R but are half the price of what Herb is asking.


Will this newer (presumably) FPU not work with the setup I'm looking for? (IIsi riser) Do I need to pony up for the original product.?

Thanks

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I've never heard of issues with different masks of m68881 or m68882. From where did you get the impression that it might be an issue?

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2 minutes ago, johnklos said:

I've never heard of issues with different masks of m68881 or m68882. From where did you get the impression that it might be an issue?

From my own ignorance, to be honest. I'm a curious person with a lot of interests, but by no means formally trained in electrical engineering or computer science. I think understand the concepts of masks—it's similar to a photographic print/copper plate meant to selectively preserve the die's resist to etching, yes?

I wondered if there would be any incompatibility between the two masks, not knowing completely what those differences are.

Thank you though for confirming that there shouldn't be any issues on that front.

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Masks refers to the photo mask set used to "print" the parts on the silicon wafers.

Mask changes are done for a variety of reasons. To fix bugs, or process changes, or shrinks.

The most common reason for different rev numbers are for shrinks or different packages. (Plastic vs. ceramic.)

 

I would expect for use in a Mac that all the 68882's would be functionally identical, the only difference would be packaging. (Plastic vs ceramic.)

Exact differences will documented in the Motorola spec sheets.

Imo, any 68882 that will physically fit in your socket should work.

 

I worked at Motorola for many years.

C74N ('030) and C12R are two numbers I remember very well as I ran thousands of wafers of these back in the "old days".

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