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#117588 07/24/20 07:52 PM
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robcfg Offline OP
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Hello, fine people!

I was trying to run the Acorn Electron driver, and I realized something odd with the roms for it.

I checked the service manual and it turns out that the Electron has one 32KB rom chip (27256 compatible) but when I do a listroms for the Electron driver, all roms are 16KB, which is not correct.

So, as I have my Electron at hand, I dumped the rom chip, and as I suspected, MAME didn't recognize it. If I separate the file into two 16KB files, MAME recognizes the first part as the basic rom, but cannot recognize the second half, which should be the OS rom.

MAME doesn't recognize the OS rom that works with elkulator or electrem either.

The SHA1 sum for my file is 4a66c83aba07d0a8e76ed8a5545af04e11c19fdc.

Should I upload it somewhere?

Cheers,
Rob

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There's a pretty good chance there were multiple revs of the board with different sized ROMs, that happens a lot because the next size up gets cheaper after you've been in production a year or two.

I'll let Pernod decide how to handle this, because he's touched that driver earlier today.

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robcfg Offline OP
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Ok, thanks!

I'll put the dump his way laugh

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RB is correct in that there were multiple issues of the board where earlier examples came with the OS and BASIC on separate 16K ROMs.

Every Electron emulator comes with a slightly different OS ROM, all differing by a few bytes in the region mapped between &FC00-&FEFF. This region is reserved for IO and so contains no code, and actually contains credits to Acorn staff. All other Acorn MOS also contain a variation of credits in this region. The bytes that differ suggest they were saved from a running machine and so have bytes of IO mapped over the ROM. I actually thought we already had a clean dump, seems not.

I've checked your dump and am happy with it so will get it submitted tomorrow. I'll also have to make a minor change as currently the OS and BASIC ROMs are loaded into separate regions, so will have to adjust to access both ROMs from a single region. Thanks smile


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robcfg Offline OP
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Thanks a lot!

I still find it funny that the service manual only mentions the 32KB rom, and the empty socket with A14 (I think) tied to +5V.

Also, I’ve seen some pictures around where the empty socket is not present, but none with two rom chips.

I guess that’s life... laugh

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Originally Posted by robcfg

Also, I’ve seen some pictures around where the empty socket is not present, but none with two rom chips.


Here's an early version with two ROMs:
[Linked Image from computinghistory.org.uk]


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robcfg Offline OP
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Nice!

The mask rom in your picture is a 613128 instead of the 613256 on my board, which makes sense.

Can the driver be made to accept both configurations?

Thanks a lot!


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