Overclocking & 68010: Annotated Compatibility List

[MegaDriver]

The Schmitt Trigger Inverter I used was a HD74LS14P. Its datasheet is here:
http://documentation.renesas.com/doc...9_hd74ls14.pdf

Barone, I could only find SN74LS14N chips. Do you know if these are the same or equivalent?

[MegaDriver]

six (awesome) pages and still no mention of Gens 15 Mhz emulator. Race Drivin becomes a SVPesque quality game framerate wise. Road Rash II becomes an awesome looking game and very playable. Can't wait to test it on FPS, rail shooters & polygon games.

Sorry if this is off-topic, but how can one make Gens run at 15Mhz?

[MegaDriver]

Well, I decided to try iy anyway.

And it works!

I socketed the oscillator so I could experiment different clock speeds.

I then added the small IC SN74LS14N on another piece of board.

8 MHz is barely noticeable, but 9.21 MHz and 10 Mhz do give a perceptible boost in performance.

I have not built the halt switch and the console boots from cold start with overclock!

Surprise, surprise, my Mega games 1 cartridge with Super hang on plays almost flawlessly at 10Mhz while my other Super hang on japanese cartridge crashes all the time.

Turbo Outrun also plays fine.

I spent a nice gaming moment this afternoon.


Here is how I did it:

[Barone]

Super Hang On still haunts me a great deal.

I noticed that there is comment on the list: "sheath reported sound issues depending on the original cartridge used. Some copies work perfect, others have issues".

I have a japanese cart and the sound issues do happen when I overclock the megadrive.
But are there japanese carts that work flawlessly?
How can anyone tell the difference between the two types?
Isn't the ROM used the same? So, how can some cause sound issues and others do not?

I had a japanese Super Hang-On which had the Rev00 version on it and I could push 12 MHz on it without any issues.
I GUESS that it might have been a later batch of the Rev00 with faster ROM chip on it. I GUESS. This is the only explanation which seems reasonable to me.

Barone, I could only find SN74LS14N chips. Do you know if these are the same or equivalent?

Well, as long as it's a Schmitt trigger it should perform the same.

Well, I decided to try iy anyway.

And it works!

Awesome! And thanks for sharing the info. Rep given.

8 MHz is barely noticeable, but 9.21 MHz and 10 Mhz do give a perceptible boost in performance.
I have not built the halt switch and the console boots from cold start with overclock!

I'm very happy for you. Good job!
Yeah, like I said, the Schmitt trigger is good to make the circuit reaches stability quicker too.

Surprise, surprise, my Mega games 1 cartridge with Super hang on plays almost flawlessly at 10Mhz while my other Super hang on japanese cartridge crashes all the time.

That's some NICE piece of info there.
I didn't know until now that the Mega Game Vol.1 contained the unsensored-harder-good-for-overclock Rev00 version of Super Hang-On (yes, I double checked it on an emulator after reading your post). It's nice because we can now recommend that version (which is cheap in Europe AFAIK) to the ones which want to play it overclocked with an official cartridge.

Again, I believe the older Japanese cartridge might be using a slower ROM chip which can't handle the faster accesses required by the overclocked system. That's my guess.

Turbo Outrun also plays fine.

I spent a nice gaming moment this afternoon.

Awesome. And thanks for the pictures too.

Aliás, sempre bom ver um patrício por aqui. Grande abraço!

[MegaDriver]

Aliás, sempre bom ver um patrício por aqui. Grande abraço!

Barone, tive muito gosto. Valeu!

[MegaDriver]

I had a japanese Super Hang-On which had the Rev00 version on it and I could push 12 MHz on it without any issues.
I GUESS that it might have been a later batch of the Rev00 with faster ROM chip on it. I GUESS. This is the only explanation which seems reasonable to me.

I decided to go for overclock just because of SHO. Probably one of the first games I played on the arcades and which I keep fond memories of.

The first time I tried to overclock a model 1 MegaDrive things didn't work out very well in spite of all the trouble I had so I stopped trying and stored the MD. It was the overclock method of using the clock signal left in the board of 13 Mhz.

I wanted the maximum with no extra parts! Suffice to say I made a terrible mess.

Geez, I wish I knew that 9 or 10 Mhz were this good!

However, I recall there was one experiment among many that gave some good results with that SHO japanese cartridge (albeit with some sound issues also). Today I know that what I used was a schmitt trigger too but I was advised by a person with much more knowledge in electronics than me to choose a slightly different one after he probed the board. I still don't understand very well his approach but it kind makes some sense now, I suppose.

I will have to retrieve my other MD from storage and open it up just to show you what was done back then.

I remember it was a somewhat crude job but at least it got things going.

Hang-on for the pictures!

[MegaDriver]

So, as promised, here are the pictures I took:
















And the stories behind the pictures are, as far as I can remember, the following:


- CPU was changed to 68000P10 because I mistreated some pins and we didn't know if I had destroyed the P8 or if it was being pushed too far with the ~13 Mhz clock speed. Besides being a spare we had at hand, supposedly P10 should take 13MHz with less chances of being damaged (?). Really unsure if that actually made a difference, but we had to exclude that as a possible cause for malfunction.

- VDP on the left was getting alarmingly hot @13Mhz so one piece of thick aluminium was cut and bonded with thermal tape to improve heat dissipation. There was the suspicion that vdp could be overheating and causing lock-ups or crashes. I think this is something often overlooked and could be a matter of importance.

- Clock signal on the board had to be picked on the right side of the small coil. I can't remember what was the reason for that now.

- Halt switch was built as advised and allows clock speed change with safety.


Upon these changes overclock was possible @13Mhz but it caused a very strange effect on the graphics. I remember the screen was all garbled and full of artifacts but the games kept running and didn't actually crash. It was simply impossible to play something without making out what was going on the screen!

Conclusion was that clock signal was unsuitable for CPU in that state and had to be treated somehow.


- So, clock signal was linked to the IC on the veroboard, which is a Schmitt trigger, but had to be that particular type because it has something to do with TTL levels. It seems not all Schmitt triggers are the same regarding input signal nature and those we tried before prooved unsuitabale. Suprisingly that one did the trick and the graphics returned to normal. I consider this the real breakthrough.


Bear in mind that this was the result of experimentation and is far from perfect. I cannot even guarantee it will not do any damage eleswhere, so should anyone try it will be at his/her own risk. But it made possible to play some games @13Mhz the best way we managed at the time, in spite of sound issues and the occasional freeze.


I hope some of you can make sense out of this and perhaps it provides some clues that can help to improve the quality and stability of the modification.

[MegaDriver]

Just tried this one today and thought I should report here:
Spiderman vs Kingpin works overclocked (Spidey and enemies move faster), but @10 mhz it seems too much, perhaps a lower value will be better.

[ArcadeTV]

May I introduce my very first steps in MD-overclocking.. the Hyperdrive PCB.
It's a CPU-drop-in-replacement for MD/Genesis Model 1. There are 2 xtals on the board, allowing 4 different frequencies to chose from, activated by grounding one of the four activator-pads, so this is also compatible for new switchless mods or uController-projects. There's a pad for cpu-/HALT also. You can easily test any 68K-cpu through the PLCC-socket.
Please note that this is completely untestet, I ordered a bunch of pcbs but they didn't arrive yet. Just wanted to share this with you guys.


LATEST UPDATE 12.1.2016

PCB Version 20160112.2

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SCHEMATICS

hyperdrive_schematic.jpg



Parts-List:
MOUSER Shopping-Cart for v20160112.2 (without pinheaders and socket-headers)
https://www.mouser.com/ProjectManage...sID=1085ab6e9c

• 1x 100nF (0805)
  https://www.reichelt.de/Bauelemente/...X7R-G0805+100N
  http://www.mouser.de/search/ProductD...1BR71H104KA01L
• 2x 100pF-150pF (0805)
  http://www.reichelt.de/Bauelemente/N...NPO-G0805+150P
  http://www.mouser.de/search/ProductD...1A5C2E101JW01D
• 4x 2K2 (0805)
  https://www.reichelt.de/SMD-0805-2-2...EARCH=2k2+0805
  http://www.mouser.de/search/ProductD...yERJ-6GEYJ222V
• 2x Pinheader 1x32pin (2.54mm Raster) precision-type
  http://www.ebay.de/itm/1-SET-10-10-P...-/281798874781
• 2x 32-pin socket-header (2.54mm Raster) precision-type
  http://www.ebay.de/itm/1-SET-10-10-P...-/281798874781
• 1x Oscillator 10MHz
  OSZI 10,000000: Quarzoszillator, 10,0 MHz bei reichelt elektronik
  http://www.mouser.de/search/ProductD...45T-2C-10M0000
• 1x Oscillator 12MHz
  OSZI 12,000000: Quarzoszillator, 12,00 MHz bei reichelt elektronik
  http://www.mouser.de/search/ProductD...O45-3C-12M0000
• 1x PLCC68 Socket
  https://www.reichelt.de/PLCC-Sockel/...&ARTICLE=14703
  http://www.mouser.de/search/ProductD...468-11B1-RK-TP
• 1x SN74CBT3125DR (Texas Instruments)
  http://www.mouser.de/ProductDetail/T...D6MAkDRxlvc%3d
• 1x Motorola 68000 CPU PLCC68
  8-12MHz
  e.g: http://www.ebay.de/itm/201143947985

PCB-Ordering and Specs:

PCB-Specs:
5x10cm max >> https://www.itead.cc/open-pcb/pcb-pr...-10cm-max.html

itead_hyperdrive.png



Installation (Mockup)

hyperdrive_position.jpg


GERBER files download: https://www.dropbox.com/s/hjxu8rfw56...112.2.zip?dl=1

[ArcadeTV]

Received these 5 Minutes ago.
I'd like to give away 3 of these to anybody who wants to try it out for free.

[Barone]

It looks pretty cool. I've always wanted someone to come up with some sort of "accelerator" (alas Amiga stuff) for the Mega Drive.

[ArcadeTV]

I've always wanted someone to come up with some sort of "accelerator" for the Mega Drive.

Let me know if I you want one, I've got ONE left.

Here's my assembly-guide:
https://plus.google.com/u/0/photos/1...97703220866929

[Segaedge]

Received these 5 Minutes ago.
I'd like to give away 3 of these to anybody who wants to try it out for free.

Wow this is my dream come true! Where do I sing up to get one of these boards?

[Helder]

Nice board! I've been working on something for the Model 2 which I think some people might like, it's a nice little mod that you can adjust the speed of the clock with a pot from 7.52MHZ (slightly lower than stock clock at lowest setting) and 12.2MHZ at highest setting. This can be useful to test different games that crash at certain speeds while others are fine, I know that without an Oscilloscope it can be hard to pin point the exact clock but usually in the middle is 10mhz.

I'll be selling these kits in the Marketplace and like to offer 1 to Barone and ComradeOj since they are doing a majority of the testing for us all and this might help further more testing if they want one.

The mod is based off of the LTC1799 Clock generator to achieve the speeds:








Depending on the pot used you can either make it discreet and internal and use a small Philips screw driver to adjust speed or non discreet install with standard pot:

[stika]

this thread is making me want to overclock my Mega Drive model 1, but I dare not touch it. I don't know anything about this sort of stuff.

With that said, I would love to see people post videos of how the following games run on an overclock Mega Drive:

LHX Attack Chopper
Mig-29 Fighter Pilot
F-117 Night Storm
Steel Talons
F-15 Strike Eagle II