Any info about Platinum //e mobo revisions? And sockets too.

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Joined: May 27 2009
Posts: 922

I was looking around the net for info that explains the differences in the revisions of the Platinum //e motherboards.

I have 4 of them right now, revisions, D,E, and F. And I'm wondering what the differences are. Visually, some of the minor parts like resistors and capacitors are different colors or slightly different shapes. But that could be simply because of suppliers and what was available for production.

The rev letter is stamped right above slot 5.

Granted, the //e Platinum is the most cheapest of the 2 series. It may also be the most reliable and durable due to lower parts count and even lesser socket count.

Also, does anyone know why they soldered in the IOU and not the MMU? Why not both? Why not leave them socketed. Same goes for the other chips. Some are socketed and some not. I can understand sockets for the CPU and Keyboard controller and its Rom and the VCG.

There are also some basic gates of the LS series that are socketed. And some not.

Basically, what determined whether a chip got a socket or not?


On a clear disk you can seek forever..

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speedyG's picture
Joined: Nov 16 2011
Posts: 2376
Re: Any info about Platinum //e mobo revisions? And sockets too.

Hallo Keatah,
to be honest I didn´t understand that logic at anytime because some of the changes haven´t been very logic. As i explained in the other thread the IOU for example had been dependent to the timing of the Videosignal and there had been versions for the NTSC ( i.e. for U.S. ) and PAL ( i.e. Europe ) and therefor up to my guess its not very intelligent to solder that chip because it´s thereafter not very easy to change from NTSC to PAL as is was with socketed models where just the chip could be swapped. Of course this is just a private mind....

by technical view the only possible explanation could be the fact that the timing in the //e always had been quite critical in different parts of the board....

this might be related to the fact that apple decided to shrink the amount of chips by integrating them in the Programmen Logic Arrays and therefor there was not much experience in those days with that chips ( fast change of chip-models ) and therefor the revisions were some kind of "learning by doing" and the fact that timing differences within that "Large Array Chips" issued problems to the busses outside....

it might have turned out that the timing issues could have only been solved with several chips soldered for better connection and timing at the "border values" meaning not the cycle of the pulse but more the precise few nanoseconds of the fall or the rise of the ends of the pulses....

with higher frequencies this issues start to raise ( thats ths reason that in modern boards nearly nothimg is socketed ! ). So the problem might have exceeded and the numbers of repairs started rising up with sockets remaining in the board and dropped again when the chips were soldered... normally in those days techniciens prefered for service reasons to keep the chips socketed - but in the special challenge to beat issues with the timing probably this favored policy was dropped to reduce service events.
And of course sockets raise the price.... with few boards this might not be important - but with large amounts the pennies add up to dollars...

another point that often is forgotten : the changing power of the both Steves in the company in that days... while the days Wozniak had more power the balance went for technical points and the days when Jobs got the points and executed his power the "merchant" carried out the fight for cutting cost... you must remember that in that years of the mid 80´s the fight between Wozniak and Jobs was just swapping up higher and higher - while both wanted to kick each other out of the company.....
this had also results in the assembly of the computers...
regards speedyG


In early days I had a lot of money but no time - now I have no money but a lot of time....
the second part includes less friends but a lot more joy on life....

gsmcten's picture
Joined: Oct 4 2005
Posts: 2609
Re: Any info about Platinum //e mobo revisions? And sockets too.


Go Here:

Read Chapter 7, or if you want you can read the entire History. It explains a lot. Smile


Steven (gsmcten)

"Apple ][.....It's ALIVE!!!!!"

Joined: Jan 24 2005
Posts: 356
Re: Any info about Platinum //e mobo revisions? And sockets too.

There are a few mainboards out there with soldered MMUs, but the main reason it's (preferably) not soldered was because of the rarely seen 8/16 option boards available from Applied Engineering, Checkmate (and a few others).

Also, the MMU and several other IC's were considered service parts.