My modded Genesis (dialup warning) - Page 1
Forum section: electronics / projects

author: lnx64
author_rank: Regular Contributor
timestamp: October 26, 2013, 05:41:18 pm
content: Well, I figured I'd make a whole thread for this. I wanted to first let you know that, yes, I could have wired this better, but for now it works well (minus some slight freezing in overclock mode, as my oscillator isn't outputting a square wave per my other thread..).Room for improvement, especially my dual sound chip mod with it's point to point wiring, that is only temporary right now as it's still being worked on. I use thin wires for the higher frequency stuff, and slightly thicker wires for anything carrying VCC or GND, as I was once told to do.http://img.photobucket.com/albums/v395/Evilweredragon/Sega%20Genesis%20Mods/back_zps546ea8c8.jpg~originalYou can see the 10MHz oscillator in back right next to the CPU it's overclocking. I did this to keep it as close as possible so the wire wasn't long at all.https://fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-prn2/1397154_10200851797921318_1175325986_o.jpgThe wire is soldered much cleaner than it appears in this picture.. Not sure why my camera made it looked like it was so badly soldered when it's actually very clean.https://fbcdn-sphotos-f-a.akamaihd.net/hphotos-ak-prn2/1052835_10200851874683237_69930399_o.jpgI chose that spot for the 10MHz oscillators clock as it was the closest 5v location for the oscillator.. Didn't want a long run.http://img.photobucket.com/albums/v395/Evilweredragon/Sega%20Genesis%20Mods/IMG_1971_zps20d617c6.jpg~originalNow, explanations.Region mod - Because sometimes I like my imports, and some games really need the system in 50Hz (as it's a 60Hz console).CPU's replaced with more robust versions - The Z80 was replaced with a part that is able to withstand more heat. I don't plan to overclock the Z80 so I don't know exactly why I did this. The 68000 was replaced with a ceramic version designed for medical/military use. It's 12Mhz as far as I know, and actually runs cooler at stock speed than the original signetics part. Maybe it's CMOS? Not sure. But I got it because it seemed better for an overclock to 10mhz, since it's rated for 12MHz.. To me this keeps it well within it's reliable limits, and any crashes shouldn't be because of the CPU.Real SRAM - The Genesis by default, uses PSRAM for it's 68K RAM.. It has a slower speed than true SRAM, and is really just DRAM in disguise without needing external refreshing circuitry. I did this just because I thought it would improve the overclocking. It didn't change it one bit, but hey, socketed RAM, cool!Gold plated stereo RCA jacks - Kinda a simple mod really, and done just simply because I don't like running a cable from the front of the system for stereo sound. I chose gold plated RCA jacks not because they look cool, but because I had regular radioshack connectors there and they kept corroding, so I needed something corrosion resistant.YM3438 / Dual sound chip mod - This is one that I had been pondering around for a bit. The later model 2's used a YM3438 in their ASIC instead of the YM2612. While by default they sound terrible, with mods they can actually sound really nice because they actually have a better DAC built in than the YM2612, allowing for a cleaner sound. So I figured the discrete YM3438 would be the same. Not quite, in the end the DAC was 9-bit rather than the YM2612's essentially 8-bit DAC (whereas the ASIC version in the model 2, was I believe 14-bit or something like that). It does sound a little nicer, and louder, but very close to the original. Some problems though I ran into, is the YM3438 is not directly compatible with the YM2612 software. Sonic spinballs sound driver crashes when leaving options, super fantasy zone plays music far too fast, etc. So I had to come up with the dual sound chip mod, which disabled the YM2612's sound output, but used it for responding to the console for it's other parts. The YM3438 was put in a mode that it only reads the bus, but never responds.. So basically YM2612 conducts, but the YM3438 sings.. It worked quite well, and sounds decent:http://www.mediafire.com/listen/yi83xhaxha0jx2i/11_Level_3_-_Tea_Time!.mp3And lastly, the removal of the LM7805's for DC buck converters. This not only lets me use a power supply with a lower voltage, but they run cold and I can remove the heatsinks from the system. This makes the Genesis use less power (I went from about 15 watts to 5 watts), and runs cold now.If anyone has an ideas for improvement, advice is welcome.. This system used to have an RF shield, but it had to be removed because the oscillator wouldn't fit. I may try and work a way to fix that, because I do want the RF shield back in it.

author: lnx64
author_rank: Regular Contributor
timestamp: October 26, 2013, 11:06:28 pm
content: Here's more sound samples of the dual sound chip mod. I changed resistor values to make it not clip so loudly.http://www.mediafire.com/listen/kx9te3t4w3t7yd1/TF4-0.mp3http://www.mediafire.com/listen/ees12ukcdcb880o/TF4-1.mp3http://www.mediafire.com/listen/hs571935i1fzzwq/TF4-2.mp3http://www.mediafire.com/listen/dh4deqi5hymxvx0/TF4-3.mp3http://www.mediafire.com/listen/pcd7stxli8ia9yh/TF4-4.mp3http://www.mediafire.com/listen/qphc35nw8m8o1qs/TF4-5.mp3http://www.mediafire.com/listen/nwx3wsl3l2oi8f9/TF4-6.mp3http://www.mediafire.com/listen/d6k2ejf7pyw8cy7/TF4-7.mp3http://www.mediafire.com/listen/gba2q7ivbxruqgy/TF4-8.mp3

author: jeremy
author_rank: Super Contributor
timestamp: October 27, 2013, 12:06:57 am
content: This is great! It really does sound very good! Love the ceramic CPU as well

author: lnx64
author_rank: Regular Contributor
timestamp: October 27, 2013, 12:37:07 am
content: Thanks, I actually found that CPU in a bin of parts like 10 years ago. I was like, that package looks like a 68000, but, it's not marked as such. I in a blind attempt to try it, found it worked just fine in a 68000 system. So, it worked great, and later I finally found it's it's an HP part number for a military specced 68k.. This was awesome, and I use it in my Genesis now.

author: true
author_rank: Frequent Contributor
timestamp: October 27, 2013, 04:09:37 am
content: Improvement? Record music from games I am familiar with so I can hear the difference

author: lnx64
author_rank: Regular Contributor
timestamp: October 27, 2013, 04:25:44 am
content: What games are you familiar with?Though I gotta admit, the mod was already done, I'd have to un-mod it to get before's. lol

author: krenzo
author_rank: Regular Contributor
timestamp: October 27, 2013, 05:14:41 am
content: Record music from Streets of Rage.BTW, that Titan demo is awesome.

author: lnx64
author_rank: Regular Contributor
timestamp: October 27, 2013, 05:33:33 am
content: Quote from: krenzo on October 27, 2013, 05:14:41 amHere you go.http://www.mediafire.com/download/q1v27fldgw4637r/sor.flachttp://www.mediafire.com/download/c0cpwh30nt4v24p/sor2.flacYou will find in these clips there's some digital noise. This was actually a problem from when I recorded these samples, as if you hear the other samples, there's no digital noise in them. Otherwise, audio dynamics are the same as they were before.PS: What makes that Titan demo, is that, at 4:54 to 5:09, it breaks the graphics chips 64 colors on screen limit, and pushes the entire systems 512 color palette, on the screen at the same time. So it's actually showing more colors than even the SNES could do. This is supposedly due to a new programming technique where each color can be addressed per-pixel vs a color table. A shame no game ever used that, though if I remember Toy Story came very close.

author: marshallh
author_rank: Unknown
timestamp: October 27, 2013, 05:44:27 am
content: WISE FWOM YOHR GWAVE

author: lnx64
author_rank: Regular Contributor
timestamp: October 27, 2013, 05:55:29 am
content: Quote from: marshallh on October 27, 2013, 05:44:27 amI'll get some Altered Beast tomorrow.Sadly I don't think it as a sound test, so I'll need to play the game for a sample.

author: lnx64
author_rank: Regular Contributor
timestamp: October 27, 2013, 05:24:23 pm
content: Here you go, as promised.http://www.mediafire.com/listen/53a58jbr64wov0j/alteredbeast.mp3

author: marshallh
author_rank: Unknown
timestamp: October 27, 2013, 05:43:06 pm
content: Had another laugh, that voice is so badPOWAH UNGH

author: lnx64
author_rank: Regular Contributor
timestamp: October 27, 2013, 06:01:36 pm
content: Quote from: marshallh on October 27, 2013, 05:43:06 pmThis was actually not because the hardware couldn't produce clear PCM sound, it was more simply ROM space. They couldn't fit all those samples on the cartridge. The "ha ha ha ha ha!" at the end of the stages was pretty clean though, though it honestly sounded like the samples weren't all recorded on the same equipment.