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View topic - Mark III + SK-1100 (Faulty?) + Basic

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  • Joined: 01 May 2022
  • Posts: 1
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Mark III + SK-1100 (Faulty?) + Basic
Post Posted: Sun May 01, 2022 3:39 am
Hi, happy to find this forum.

I've got a question or two.

I have a beautiful Mark III and SK-1100 keyboard but I could not find a BASIC SK-III cartridge or ROM anywhere, so I settled for version "II B", but I cannot get the keyboard to type. If I wiggle the ribbon cable, random characters will spam the screen.

I would really like to program on the Mark III itself for that authentic 1984 experience.

Any help?
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  • Joined: 25 Feb 2013
  • Posts: 384
  • Location: Osaka
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Post Posted: Mon May 02, 2022 8:52 am
I would try to clean the contacts both on the mark 3 and on the keyboard connector. For the latter you may consider something like this
https://aliexpress.com/item/4000468868208.html
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  • Joined: 05 Nov 2014
  • Posts: 435
  • Location: Auckland - NZ
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Post Posted: Wed May 04, 2022 12:15 am
What is the difference between the basic carts for the sc3000 the ones for othe MkIII? Is it just to do with the internernal memory? If i remember rightly the MkIII doesnt have all the memory control lines for dram on the cart connector, so they likely changed to sram?
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  • Joined: 19 Apr 2019
  • Posts: 19
  • Location: Canada
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Post Posted: Sun Aug 14, 2022 8:21 pm
wasup wrote
What is the difference between the basic carts for the sc3000 the ones for othe MkIII? Is it just to do with the internernal memory? If i remember rightly the MkIII doesnt have all the memory control lines for dram on the cart connector, so they likely changed to sram?


That would be my guess. Working on this theory, I made a homebrew "SG-1000 BASIC IIIB" cartridge using a "Sega SC-3000 BASIC Level 3 v1.0 (1983)(Mitec)" ROM (CRC32 5d9f11ca) and a 32K SRAM chip, although I am running into the same problem with the keyboard seemingly doing nothing on an SG-1000 II.

For what it's worth, the same ROM has the same problem in MAME 0.243, where the SC-3000 is configured as an SG-1000 with an SK-1100. That is likely a different issue, though, as I'm seeing some similar weirdness in general with that emulator when running some other keyboard carts like Music Editor.

I do have a real IIIA cartridge, but I'm guessing since it uses DRAM and the SG-1000 doesn't expose those DRAM refresh lines either, it won't work properly. My SG's expansion connector looks a little rough, so if cleaning it doesn't work, I might take the top off the keyboard/SG and see if I can see /KBSEL cycling...?

The INS/DEL key on the keyboard and the arrow keys don't seem to be able to control games like they can on the SC-3000.

edit: I suspect I may have some other issues with this BASIC, as pushing the joypad buttons seems to get picked up as "row 0" of the keyboard matrix (1, Q, Z, etc.) Will try it with the Mark III and my SG clone tomorrow.
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  • Joined: 19 Apr 2019
  • Posts: 19
  • Location: Canada
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Post Posted: Tue Aug 16, 2022 2:44 am
leadedsolder wrote
wasup wrote
What is the difference between the basic carts for the sc3000 the ones for othe MkIII? Is it just to do with the internernal memory? If i remember rightly the MkIII doesnt have all the memory control lines for dram on the cart connector, so they likely changed to sram?


That would be my guess. Working on this theory, I made a homebrew "SG-1000 BASIC IIIB" cartridge using a "Sega SC-3000 BASIC Level 3 v1.0 (1983)(Mitec)" ROM (CRC32 5d9f11ca) and a 32K SRAM chip, although I am running into the same problem with the keyboard seemingly doing nothing on an SG-1000 II.

For what it's worth, the same ROM has the same problem in MAME 0.243, where the SC-3000 is configured as an SG-1000 with an SK-1100. That is likely a different issue, though, as I'm seeing some similar weirdness in general with that emulator when running some other keyboard carts like Music Editor.

I do have a real IIIA cartridge, but I'm guessing since it uses DRAM and the SG-1000 doesn't expose those DRAM refresh lines either, it won't work properly. My SG's expansion connector looks a little rough, so if cleaning it doesn't work, I might take the top off the keyboard/SG and see if I can see /KBSEL cycling...?

The INS/DEL key on the keyboard and the arrow keys don't seem to be able to control games like they can on the SC-3000.

edit: I suspect I may have some other issues with this BASIC, as pushing the joypad buttons seems to get picked up as "row 0" of the keyboard matrix (1, Q, Z, etc.) Will try it with the Mark III and my SG clone tomorrow.


OK - this does appear to have simply been a dirty/corroded connector on the SG-1000 II. I wrote a quick program to do the keyboard detection, and then kept turning the machine off, pulling the connector out a bit, and starting the machine until it detected the keyboard. After that, BASIC III-B seems to work properly!

I will take it apart and give it a thorough scrub later. At least I know the keyboard is working!
IMG_0711.JPG (2.11 MB)
My RAM test program with a "keyboard detected" thing in the corner
IMG_0711.JPG
IMG_0710.JPG (4.18 MB)
BASIC running with the classic hello world program
IMG_0710.JPG

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