Cosam
@cosam-the-great.bsky.social
Messing with retro stuff, with varying levels of success.
https://ko-fi.com/cosam
https://www.youtube.com/@cosam2
https://ko-fi.com/cosam
https://www.youtube.com/@cosam2
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.
November 14, 2025 at 5:12 PM
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.
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.
November 12, 2025 at 4:58 PM
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.
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.
Here's an interview with @cosam-the-great.bsky.social, the dev who created the Neptune and other awesome retro motherboards. As always, these long-form chats are available everywhere - Just search your favorite app for "RetroRGB Cosam", or go to the main link here: www.retrorgb.com/interview-wi...
September 29, 2025 at 6:51 PM
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.
Reposted by Cosam
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 :(
August 7, 2025 at 2:27 AM
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 :(
Reposted by Cosam
July 5, 2025 at 3:01 PM
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...
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...
github.com
June 23, 2025 at 11:51 AM
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...
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...
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 ...
github.com
June 5, 2025 at 1:09 PM
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...
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.
June 4, 2025 at 9:35 AM
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.
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...
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...
github.com
May 23, 2025 at 12:12 PM
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...
Reposted by Cosam
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-...
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...
www.retrorgb.com
May 14, 2025 at 12:39 PM
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-...
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 - 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.
github.com
May 5, 2025 at 10:12 AM
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...
Woohoo! Nice work Dennis, now it's verified I'll be publishing the project any time now, including preliminary schematics.
This took forever, and have gone through a great deal of my spares trying to find a working screen, but it’s finally verified..
@cosam-the-great.bsky.social’s PC Engine GT repro board works! ❤️
@cosam-the-great.bsky.social’s PC Engine GT repro board works! ❤️
May 3, 2025 at 6:21 PM
Woohoo! Nice work Dennis, now it's verified I'll be publishing the project any time now, including preliminary schematics.
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...
April 14, 2025 at 1:33 PM
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...
Reposted by Cosam
It’s alive!!
Thanks @cosam-the-great.bsky.social for the awesome project. Definitely the hardest project I’ve ever attempted.
Thanks @cosam-the-great.bsky.social for the awesome project. Definitely the hardest project I’ve ever attempted.
April 4, 2025 at 11:37 PM
It’s alive!!
Thanks @cosam-the-great.bsky.social for the awesome project. Definitely the hardest project I’ve ever attempted.
Thanks @cosam-the-great.bsky.social for the awesome project. Definitely the hardest project I’ve ever attempted.
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.
March 28, 2025 at 11:43 AM
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.
YouTuber: "You will never own this."
PCB reproducer/reverse engineer/general weirdo: "Hold my beer."
PCB reproducer/reverse engineer/general weirdo: "Hold my beer."
March 25, 2025 at 9:33 AM
YouTuber: "You will never own this."
PCB reproducer/reverse engineer/general weirdo: "Hold my beer."
PCB reproducer/reverse engineer/general weirdo: "Hold my beer."
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?...
Someone Did What SEGA Didn't, Build A REAL Neptune | COSAM
YouTube video by Macho Nacho Productions
youtu.be
March 14, 2025 at 9:09 PM
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?...
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.
March 13, 2025 at 12:12 AM
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.
Reposted by Cosam
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!
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!
February 13, 2025 at 4:26 AM
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!
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!
Junk DD-10, busted screen, jammed drive mech, horrible gummy coating peeling off... but goodies lurk inside...
January 27, 2025 at 5:48 PM
Junk DD-10, busted screen, jammed drive mech, horrible gummy coating peeling off... but goodies lurk inside...
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.
January 25, 2025 at 11:14 PM
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.
Reposted by Cosam
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
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
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
www.4gamer.net
January 17, 2025 at 10:38 AM
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
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
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...
cosam2
www.youtube.com
January 16, 2025 at 12:35 PM
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...
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.
January 15, 2025 at 8:57 PM
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.
Epic warts-n-all write-up on the build process by Neptune pioneer and board tester extraordinaire, Aergan.
Cosam's #SEGA #Neptune (commissioned by @jake74.bsky.social )
@cosam-the-great.bsky.social : Want to build a snowma-I mean Neptune?
Me: Sure, but I have no spares.
Jake: I has spares.
Me: Ok, guess we're building a Neptune then.
First we are testing our donor HW; MD PAL VA1 and 32X PAL VA1.
@cosam-the-great.bsky.social : Want to build a snowma-I mean Neptune?
Me: Sure, but I have no spares.
Jake: I has spares.
Me: Ok, guess we're building a Neptune then.
First we are testing our donor HW; MD PAL VA1 and 32X PAL VA1.
January 13, 2025 at 9:18 AM
Epic warts-n-all write-up on the build process by Neptune pioneer and board tester extraordinaire, Aergan.