I acquired a Williams "Earthshaker!" pinball machine several years ago. It came with the version L-1 ROM installed. I noticed that sometimes balls would get stuck in the shelter kick-back-up mechanism for a bit (it seemed it didn't kick a first ball up fast enough if a second ball entered the shelter). This was fixed when I upgraded to ROM L-3.

I'm now interested in changing to to ROM F-1 which removes a less-than-completely-family-friendly word so I can feel more comfortable tinkering with the machine with my kids. But I can't tell if F-1 is the same as L-3 with just a word removed, or if it is based on a prior version and has some of the older bugs. Is there a changelog available anywhere, or anybody with experience, who can let me know what the differences are between the L-3 version and the F-1 version? Or will I just need to buy the chip with the F-1 version and try it out?

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    See discussion on if pinball is on topic – user616 Jun 9 '16 at 10:36
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    What's interesting is that this really doesn't have much to do with pinball. You want to binary compare two ROMs, really. If you can get your hands on to images you should be able to use a hex editor to see the differences. (Barring finding a reliable changelog.) – user12 Jun 9 '16 at 14:48
  • You might check this website - The Internet Pinball Database Presents - Earthshaker. Copyright notice and license agreements are included, so make sure your usage is allowed. – user3169 Jun 9 '16 at 19:18
  • @user3169 You could just about post that as an answer - its a bit weak, but its a route to at least making further investigations (and gives a low-cost checck if the op has a programmer) – Sean Houlihane Jun 9 '16 at 20:11
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    @SeanHoulihane SE generally discourages link only answers, as links change over time, and in this case the content is too broad to provide a specific summary. It would be better if the OP checks the information and then adds pertinent details to the question (as it is unclear what the OP can or is willing to do). – user3169 Jun 9 '16 at 20:35

Only the U26 and U27 ROMs provided by The Internet Pinball Database differed between versions. Here is an image representing some results of that analysis:

Two largely red rectangles, both dotted with white and some grey. The lower image has some intersecting white rectangles just right of the centre. Directly below these white rectangles is a block of grey, scattered with red, green and blue dots. Below and left of this is a partial red and white chessboard pattern.

Red, green or blue means that the byte was different only in version L-1, L-3 or F-1 respectively. White means that the byte was the same in all, and grey none. The upper half is U26 and the lower half is U27.

Disassembling is forbidden by the license, so it is difficult to be certain what specific bytes represent, but the presence of so much red shows that the L-1 version is very different to both the L-3 and F-1 versions and that the L-3 and F-1 versions are similar.

I conclude that F-1 is based on L-3, not L-1, and therefore contains the bug fixes from L-3.
For more information, please see this Retrocomputing blog post.

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    This was a really interesting project. I hope to have a blog post about it soon. – wizzwizz4 Apr 2 '17 at 8:13
  • Amazing work! I'd meant to get back to this and diff the ROMs, but never found the time. Thank you so much! – user616 Apr 3 '17 at 1:48
  • @PeterCooperJr. The blog post is now live. – wizzwizz4 Apr 15 '17 at 8:20

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