68kMLA Classic Interface

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Macintosh Plus ROM orientation
Posted by: CharlieFrown on 2016-08-03 11:01:07
Hi, 

forgot to take a picture of Hi and Lo ROMs before taking them out and cleaning them. How can I distinguish them? One of them is marked "C", the other one "B". Simple logics suggest that C is probably Hi and B is low, but wanted to make sure. 

Besides what are the symptoms of boot attempt without ROMs at all? Sounds stupid, but is it normal I get just horizontal bars?
Posted by: Godzil on 2016-08-03 12:36:56
You can find which one is by using the part number written on the chip
Posted by: bigmessowires on 2016-08-04 08:15:31
With the board oriented so that all the ports are at top, the HI ROM is at left and the LO ROM is at right. I think it's also labeled on the logic board.

rominator-installed-372-2.jpg

Horizontal bars or similar weirdness sounds about right if you have them accidentally swapped.

I don't think B / C indicates HI / LO, but rather a version number. The HI / LO is the middle digits of the part number, if I recall, like 342-0341-C / 342-0342-C.
Posted by: CharlieFrown on 2016-08-04 11:25:24
bigmess: thanks, that was helpful
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