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Old 26 September 2016, 15:48   #1
Marchie
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ROM chip sizes, burning ROMs.

I recently put a 3.1 ROM from AmgaiKit in my A2000 and noticed it was quite a bit taller/higher than my old 2.04 ROM, this is only an issue since I have an accelerator board that piggy-backs onto the 68k socket and over-hangs the ROM chip which now contacts it and causes issues.

Are all 3.x ROM chips bigger than 2.x ROMs? Or is this just an after-market AmigaKit thing?

Is it possible to transfer the 3.1 image onto my old chip? Or do they have different capacities?
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Old 26 September 2016, 16:16   #2
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The 3.1 ROM you have is most likely an EPROM, which uses a ceramic package which is a little taller than the plastic package of the original 2.04 ROM. An EPROM has a window under the sticker which allows it to be erased by exposure to UV light. It can then be reprogrammed and used again. Your 2.04 ROM is an OTP (one time programmable) ROM, and cannot be erased and reprogrammed. You can get blank OTP programmable ROMs, which have a low profile package which should fit in your A2000.
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Old 26 September 2016, 16:17   #3
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It's probably two different types of ROM chip involved. The original ROMs are permanent and have the black ceramic with etched print on top, just like most other chips. These are called "mask ROMs". The AmigaKit ones aren't permanent, but start of blank and are "burned", something similar to making a CD-R (different process of course but same general idea). These tend to be a little taller and have a glass window in the top of the chip for erasing it, and so normally it's covered with a label of some sort so they're not accidentally erased. These ones are called "EPROMs", and are often used for lower volume production.

So, to answer your other questions, the original ROMs cannot be erased so you can never transfer something else onto them, although they are the same capacity. The size is to do with the ROM type and not its capacity, so original 3.0 mask ROMs would be the same physical size as an original 2.0 mask ROM, and an EPROM 2.0 chip would be the same physical size as an EPROM 3.0 chip.

Hope that makes sense
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Old 26 September 2016, 16:19   #4
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Unfortunately no. The original 2.04 rom is a mask rom (read only). The 3.x rom is an eprom (writable). If you were to peel back the sticker you will find a little window.

I can only suggest that you purchase a kickstart switcher with a ribbon cable which will allow you to move the kickstart out of the way of your accelerator.

There is a guy over at Amibay who sells them (I can't remember his name at the moment).
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Old 27 September 2016, 02:06   #5
Marchie
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Thanks everyone!

I'm guessing that since the A2000 never shipped with kickstart 3.1 (as far as I know) that there's no such thing as a 3.1 mask ROM that will fit an A2000?

Found the Amibay guy selling kickstart switchers. Does anyone here have one? (Specifically the ribbon version). And can they confirm what the profile is? (unfortunately the photographs are all top-down).

Last edited by Marchie; 27 September 2016 at 02:14.
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Old 27 September 2016, 12:02   #6
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There probably were suitable mask ROMs available once upon a time - Kickstart 3.1 was a popular upgrade back in the day. But with only a finite number manufactured, they're probably all sold out everywhere, leaving just the EPROM versions unless you get lucky and find one second hand.
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Old 27 September 2016, 14:03   #7
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I think the only mask ROMs were made for Escom A1200 and A4000 models.
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Old 27 September 2016, 20:03   #8
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Perhaps the issue could be solved by putting an extra socket between the CPU board and the 68k socket which should lift it a bit?
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Old 28 September 2016, 01:58   #9
Marchie
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Had a closer look and the Kickstart switcher looks like the perfect solution (albeit as-yet untried).

Quote:
Originally Posted by demolition View Post
Perhaps the issue could be solved by putting an extra socket between the CPU board and the 68k socket which should lift it a bit?
Is there such a thing as a 68k socket spacer? That could work in theory although I suspect I'd start bumping up against the PSU/floppy drive chasis (I hate that thing btw...).
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Old 28 September 2016, 08:16   #10
demolition
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Quote:
Originally Posted by Marchie View Post
Is there such a thing as a 68k socket spacer? That could work in theory although I suspect I'd start bumping up against the PSU/floppy drive chasis (I hate that thing btw...).
Sure, you can just use a socket. It should preferably be the same type as you have on your accelerator to ensure a good connection between the two.
Something like these:
http://www.ebay.com/itm/6pcs-IC-Sock...kAAOSwrXdXK2PU
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