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Cosam

@cosam-the-great.bsky.social
640 followers 9 following 77 posts

Messing with retro stuff, with varying levels of success. ko-fi.com/cosam www.youtube.com/@cosam2

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Cosam @cosam-the-great.bsky.social · 14/11/2025
Debugging the SFC to CD mechacon interface. Timing to work out on the PLD side to get reliable reads/writes each way. The scope shows the individual nibbles of an ACCESS command being transferred to an ATMega microcontroller that's standing in for the real mechacon chip.
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Cosam @cosam-the-great.bsky.social · 12/11/2025
Some progress on the Nintendo PlayStation: some programmable logic acts as a bridge between SFC and CD hardware. Set up in a loopback configuration, the BIOS now thinks it's talking to the mechacon MCU. Mock firmware is ready to go once this part is debugged.
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Cosam @cosam-the-great.bsky.social · 29/09/2025
Can't imagine anyone following me isn't following Bob already, but here's us chatting about hardware preservation, the Neptune and other such topics.
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Reposted by Cosam
Rumbleminze @rumbleminze.bsky.social · 07/08/2025
My @cosam-the-great.bsky.social Neptune board up and running! Shoutouts to the @retrorgb.bsky.social and @dubesinhower.bsky.social Discords for some troubleshooting at the end. By far the hardest project I've taken on. It's a shame tariffs have put a Neptune shell out of the budget :(
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Chrissy The Retro Scamp @chris-jh.bsky.social · 05/07/2025
To help with fixing the region flicker, i made a flex pcb. github.com/Board-Folk/N...
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Cosam @cosam-the-great.bsky.social · 23/06/2025
Minor update to the Neptune PCB, mostly to better support more donor revisions. Focus of the next release will be attempting to simplify and improve composite video. github.com/Board-Folk/N...
github.com
Release r1.5 · Board-Folk/Neptune
Swap order of R544 and CE512 to prevent ringing in composite video (credit: zaxour). Allow for smaller DIP-8 oscillator package (issue #6). Move PAL/NTSC pad for DFO installation nearer to oscillat...
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Cosam @cosam-the-great.bsky.social · 05/06/2025
Neptune revision 1.4 has just been released, including the "region flicker" fix and some BOM updates/corrections. This one was a real team effort, so thanks to all who contributed! github.com/Board-Folk/N...
github.com
Release r1.4 · Board-Folk/Neptune
Fix for the "region flicker" issue due to region/version register instability (issue #3, dr-goobur) BOM correction: C12 and C14 were listed as 1uF, should be 1nF. This avoids some edge case issues ...
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Cosam @cosam-the-great.bsky.social · 04/06/2025
Thanks to the tireless efforts of the community, the Neptune "region flicker" issue has been diagnosed and fixed! To commemorate in true #Sega style, here's a service bulletin, complete with traditional inconsistent fonts and dodgy layout.
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Cosam @cosam-the-great.bsky.social · 23/05/2025
Neptune builders/users should be aware of this very weird issue. TLDR: a few games that actively access the region/version settings of the console display artifacts in certain mode combinations. If anyone has more ideas regarding the cause we're all ears! github.com/Board-Folk/N...
github.com
Region of system flickers in 240P Test Suite, Gentest Test Rom, and Version Register flickers between A1 (81 if Sega CD is attached), D5, and FF · Issue #3 · Board-Folk/Neptune
When using 240P Test Suite on the Neptune, in the bottom right corner you will notice the region of the system flicker between North America and Europe. Further investigating this, on the Gentest T...
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Reposted by Cosam
retrorgb.com @retrorgb.com · 14/05/2025
If you planned on building a #Neptune #SegaNeptune via @cosam-the-great.bsky.social’s board, you should seriously consider this pre-populated version, as it’ll make a really hard project a bit easier. Plus, Jan used great quality caps. Links and more info: www.retrorgb.com/neptune-pcb-...
retrorgb.com
Neptune PCB Kit For Sale
Consoles4U is now selling Cosam's "Neptune" Genesis + 32x PCB, with all non-proprietary parts pre-populated.  While this is still an expert-only kit, advanced users now just have to transplant the Seg...
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Cosam @cosam-the-great.bsky.social · 05/05/2025
PC Engine GT/TurboExpress main PCB repro is now public. If you have the skills and knowledge, there is still a lot to be identified on the schematic! Thanks again to @pointerfunction.bsky.social for the donor hardware, testing and troubleshooting. github.com/Board-Folk/P...
github.com
GitHub - Board-Folk/PC-Engine-GT: Reproduction PCB for PC Engine GT/TurboExpress
Reproduction PCB for PC Engine GT/TurboExpress. Contribute to Board-Folk/PC-Engine-GT development by creating an account on GitHub.
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Cosam @cosam-the-great.bsky.social · 03/05/2025
Woohoo! Nice work Dennis, now it's verified I'll be publishing the project any time now, including preliminary schematics.
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Cosam @cosam-the-great.bsky.social · 14/04/2025
Reasonably convincing except for the lack of volume knob and ISA bracket. No actual audio coming out of it yet, I suspect my AliExpress special AY chips may not be 100% genuine...
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Tubo @xtubo.bsky.social · 05/04/2025
It’s alive!! Thanks @cosam-the-great.bsky.social for the awesome project. Definitely the hardest project I’ve ever attempted.
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Cosam @cosam-the-great.bsky.social · 28/03/2025
Pretty niche this one, even for me. My non-running A530 started losing pads during troubleshooting, which was going slowly without schematics. Hopefully this will kill two birds with one stone.
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Cosam @cosam-the-great.bsky.social · 25/03/2025
YouTuber: "You will never own this." PCB reproducer/reverse engineer/general weirdo: "Hold my beer."
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Cosam @cosam-the-great.bsky.social · 14/03/2025
Another top notch video from @machonachomedia.bsky.social showing far better than I could what it takes to build your own Sega Neptune youtu.be/PcP60-0NIEw?...
youtu.be
Someone Did What SEGA Didn't, Build A REAL Neptune | COSAM
YouTube video by Macho Nacho Productions
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Cosam @cosam-the-great.bsky.social · 13/03/2025
Fun little challenge for SMW veterans: complete the game as small Mario, no power ups or mid-level checkpoints. It's tricky but not as bad as you might expect.
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zaxour 阿宅 @zaxour.bsky.social · 13/02/2025
SMTendo + POW Block + @blueshell3d.com NintenDrawer = the ultimate NES of Theseus! Minimal work required: slot the CPU/PPU, solder on power/reset header and install your Power/AV module of choice and you’re good to go! SMTendo and POW Block Coming soon!
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Cosam @cosam-the-great.bsky.social · 27/01/2025
Junk DD-10, busted screen, jammed drive mech, horrible gummy coating peeling off... but goodies lurk inside...
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Cosam @cosam-the-great.bsky.social · 25/01/2025
Very early steps towards getting the CD hardware working. This is the BIOS diagnostic for the CXD1800 CD decoder chip. The SFC is reading values I have hard-wired onto the CD side of the data bus for testing purposes.
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Reposted by Cosam
4GamerNews @4gamer.net · 17/01/2025
4Gamer 🔗https://www.4gamer.net/games/999/G999905/20250117059/ 海外の技術者がセガの未発売ハード「Sega Neptune」を再現。実際にGenesis/スーパー32X/マスターシステムのカートリッジも動作 基板を作成し,当時の資料をもとに作った筐体に収めた動画も公開され,話題を呼んでいる
4gamer.net
海外の技術者がセガの未発売ハード「Sega Neptune」を再現。実際にGenesis/スーパー32X/マスターシステムのカートリッジも動作
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Cosam @cosam-the-great.bsky.social · 16/01/2025
So, now that I'm a big-shot YouTuber with over 100 subscribers... I'm thinking about making more videos when I have the time. If there's something you'd particularly like to see, head over to my poll there and let me know (or reply here if you'd prefer). www.youtube.com/@cosam2/comm...
youtube.com
cosam2
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Cosam @cosam-the-great.bsky.social · 15/01/2025
Board now runs under its own power (OK, wrong jack...). RGB video is sorted (no more external RGB amp hack) and audio is there but not 100% yet. No mean feat as A/V is all different to normal SFC or SNES.
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Cosam @cosam-the-great.bsky.social · 13/01/2025
Epic warts-n-all write-up on the build process by Neptune pioneer and board tester extraordinaire, Aergan.
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Cosam @cosam-the-great.bsky.social · 10/01/2025
youtu.be/aF1uoOP9WqM
youtu.be
Neptune Promo
YouTube video by cosam2
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Cosam @cosam-the-great.bsky.social · 01/01/2025
Don't get too excited. At the moment this is just the world's most overcomplicated yet incomplete Super Famicom.
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Cosam @cosam-the-great.bsky.social · 20/12/2024
Just a little side project: simple tester for Mega Drive/Genesis controllers. github.com/Board-Folk/M...
PCB render
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Reposted by Cosam
Chrissy The Retro Scamp @chris-jh.bsky.social · 13/11/2024
My Neptune board by @cosam-the-great.bsky.social, Fully working even SMS. I still need to buy the Neptune case for it by dvizix Originally had issues due to me adding 2 wrong resistor values on the pcba, which was messing up the video signal and allowing the 32x side to work 😂
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Cosam @cosam-the-great.bsky.social · 10/11/2024
People have been asking how they can support my various projects. I'm not in this for the money but obviously there are costs involved, so I have set up a ko-fi (see bio). Voluntary donations are much appreciated, but please don't expect special treatment in return :)
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Cosam @cosam-the-great.bsky.social · 08/11/2024
I really should stop trying to recreate PCBs whenever someone models a case for an unreleased console... @weskmods.bsky.social's fault this time.
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Time Extension @timeextension.com · 07/11/2024
Want Your Very Own Sega Neptune? You'll Need A Spare $2,600.
timeextension.com
Want Your Very Own Sega Neptune? You'll Need A Spare $2,600
"Final cost in terms of labour/time and parts was ridiculous"
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