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Sega Mark III dev/test board?
Post Posted: Mon Oct 25, 2021 7:48 am
This was auctioned last week
https://page.auctions.yahoo.co.jp/jp/auction/k1013158463

With no description other than
"マークIII/マスターシステム 開発基板 Game development セガ SEGA 315-5235 BANK 4 MARK III/MASTER SYSTEM SMS ジャンク【GM;V5824"
("Sega Mark III / Master System Development Board Sega Junk" + copied marking from some chips)

With three unlabelled (and unprotected) EPROM chips.

I won it for 52150 JPY should take a bit to arrive but normally my friend in Japan should be able to dump the EPROM earlier.

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Post Posted: Mon Oct 25, 2021 11:45 am
Wow! This has both 44-pin and 50-pin edges?
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Post Posted: Mon Oct 25, 2021 12:59 pm
We've seen double-ended dev carts before. The big cap looks like one used to retain RAM contents for a minute or two, rather than using a coin cell, which is unusual.

My understanding is that Japanese auctions often use the word for "junk" to mean "old stuff that is untested".
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Post Posted: Mon Oct 25, 2021 5:19 pm
Bock wrote
This was auctioned last week
https://page.auctions.yahoo.co.jp/jp/auction/k1013158463

With no description other than
"マークIII/マスターシステム 開発基板 Game development セガ SEGA 315-5235 BANK 4 MARK III/MASTER SYSTEM SMS ジャンク【GM;V5824"
("Sega Mark III / Master System Development Board Sega Junk" + copied marking from some chips)

With three unlabelled (and unprotected) EPROM chips.

I won it for 52150 JPY should take a bit to arrive but normally my friend in Japan should be able to dump the EPROM earlier.


Well done !
Can't wait to see what'inside ;)
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Post Posted: Thu Oct 28, 2021 8:02 am
Nice find! The capacitor you can see in picture 5 will likely need replacing. You can see that its been bent over and one of the legs has pulled out as a result.
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Post Posted: Thu Oct 28, 2021 12:09 pm
The three MBM27C512 EPROMs were dumped and match the three last 64 KB chunks of Basketball Nightmare.

[BANK4-C17-MBM27C512.bin.sms]
Size: 65536 bytes (4 pages), CRC:A1C9DC20
 0 ; 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; Sum:142726, CRC:4EF858E7
 1 ; 00 00 00 00 00 00 00 00 00 00 00 00 20 00 00 00 ; Sum:10F684, CRC:164E9267
 2 ; 40 00 80 80 40 00 80 80 40 00 80 80 40 00 80 80 ; Sum:17BAB2, CRC:9A7C4E00
 3 ; 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; Sum:18CC46, CRC:E1DE258B

[BANK4-C18-MBM27C512.bin.sms]
Size: 65536 bytes (4 pages), CRC:8CC86366
 0 ; ff 00 fd 00 7d 82 87 00 de a1 f3 00 fd 03 27 00 ; Sum:129334, CRC:713FF6AC
 1 ; 18 1e 47 a0 18 1b 47 a0 0c 0e 03 f0 0c 0c 03 f0 ; Sum:180083, CRC:104D03F6
 2 ; 00 ff 00 00 00 ff 00 00 00 ff 00 00 00 ff 00 00 ; Sum:1421B7, CRC:EE5D8C1B
 3 ; 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; Sum:10DACD, CRC:02A49217

[BANK4-C19-MBM27C512.bin.sms]
Size: 65536 bytes (4 pages), CRC:0E1B0887
 0 ; 7f 00 00 3f 2d 12 00 1e 3f 00 00 00 56 29 00 38 ; Sum:1230CB, CRC:4087B376
 1 ; 4b 01 3d 01 4b 01 4a 01 6a 01 6a 01 60 01 38 01 ; Sum:12B212, CRC:DD430837
 2 ; 76 01 48 01 75 01 76 01 47 01 48 01 48 01 84 01 ; Sum:188144, CRC:6E17E9F7
 3 ; 0d 01 0d 01 0d 01 0d 01 0d 01 0d 01 0d 01 0d 01 ; Sum:0C17CB, CRC:1B324B83


The first chunk is on a SRAM chip. I guess the dev system allowed to write code to that location, and the 3 EPROM chips were used for data which required less iterations during development.

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Post Posted: Thu Oct 28, 2021 2:56 pm
Awesome find indeed! It seems to be built in house, isn't it? There are no SEGA markings, and there're several bodge wires. Interestingly though, they have a mapper, which does not seem to be desoldered from somewhere and resoldered there (at least for what is visible on the pics)
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