With all the video MODs about, has anyone ever tried a Overclock MOD?

I just wonder if anyone has attempted a overclock MOD on either a AES or MVS. Ie, swapping the 68k for a 16mhz version and changing the crystal?. I expect other changes would be needed also but what I cant think off the top of my head.

I would be really intrested if its been done?

Raz

I have a spare MVS that I would gladly use for this project but I'm not sure about the other changes that would be needed...wouldn't the higher clock frequency also affect the Z80?

MVS boards have a single 24MHz crystal setting the clock for both CPUs, so there must be frequency dividers that divide 24MHz by two for the 68000 and by 4 for the Z80. If you install a 16MHz main CPU then you'd need a 32MHz crystal but that would give 8MHz for the Z80. Not sure if there is an easy workaround for this.

Razoola said:

I just wonder if anyone has attempted a overclock MOD on either a AES or MVS. Ie, swapping the 68k for a 16mhz version and changing the crystal?. I expect other changes would be needed also but what I cant think off the top of my head.

I would be really intrested if its been done?

Raz

Click to expand...

What good would it do? I know in 3D games it can make the game run smoother and have better fame rates.

neo_X7 said:

What good would it do? I know in 3D games it can make the game run smoother and have better fame rates.

Click to expand...

There's slowdown in 2D games, too. I'm no tech genius, but as far as I know, slowdown is caused when too much information is sent to the CPU at once and it doesn't have the power to slug through it all without some sort of visible "hiccup" (ie. the slowdown). There is a MegaDrive/Genesis overclock mod, and from what I have read it significantly improves the performance of games that had a tendency to bog the unit down. The N64 overclock mod makes games that used to have framerate issues (ie. Perfect Dark, Zelda: Majora's Mask, Conker's Bad Fur Day, etc.) move along at the optimal framerate. Playing PD with four players and rockets no longer results in game-crippling slowdown.

That being said, I don't really know what good an overclock mod for the Neo would do; the only game I can think of off the top of my head with any slowdown is Metal Slug 2 (or was it X?). Regardless, it would be cool if someone could do it.

squareh4t3r said:

There's slowdown in 2D games, too. I'm no tech genius, but as far as I know, slowdown is caused when too much information is sent to the CPU at once and it doesn't have the power to slug through it all without some sort of visible "hiccup" (ie. the slowdown). There is a MegaDrive/Genesis overclock mod, and from what I have read it significantly improves the performance of games that had a tendency to bog the unit down. The N64 overclock mod makes games that used to have framerate issues (ie. Perfect Dark, Zelda: Majora's Mask, Conker's Bad Fur Day, etc.) move along at the optimal framerate. Playing PD with four players and rockets no longer results in game-crippling slowdown.

That being said, I don't really know what good an overclock mod for the Neo would do; the only game I can think of off the top of my head with any slowdown is Metal Slug 2 (or was it X?). Regardless, it would be cool if someone could do it.

Click to expand...

It was Metal Slug 2, X was made because to many fans complained about the slowdown in 2.

MKL said:

MVS boards have a single 24MHz crystal setting the clock for both CPUs, so there must be frequency dividers that divide 24MHz by two for the 68000 and by 4 for the Z80. If you install a 16MHz main CPU then you'd need a 32MHz crystal but that would give 8MHz for the Z80. Not sure if there is an easy workaround for this.

Click to expand...

Well, the easiest way I can think of is to cut the CLK trace to the 68K, then get a 16MHz crystal and connect it diretly to the CPU. It wouldn't effect the rest of the board, and you could even setup a switch to change between 12 and 16MHz.

A good demonstration is to run Last Resort, second level, a tunnel of turrets

Less slowdown on the MVS motherboards that have been built in later years than say the first edition MV1.

Reznor007 said:

Well, the easiest way I can think of is to cut the CLK trace to the 68K, then get a 16MHz crystal and connect it diretly to the CPU.

Click to expand...

Or an oscillator to make it easier.

BTW anyone know where to get a 16Mhz 68000? So far I've only seen 8 or 10Mhz ones...

Shock Troopers 2 has a damn lot of slowdown in 2 player mode as well.

And of course, Twinkle Star Sprites is famous for its slowdown, which is commonly looked at as a gameplay element (and emulated in the DC version).

There are a few possible issues I can think of though as my hardware knowledge isnt as good as your a expect I could be wrong.

Possible problems I can see are;

- VRAM reading and writing being to fast. The normal work ram reading and writing shouldent be a problem because of the waitstates but VRAM is only a port and things could get read/written to fast for it to translate.

- Possible problems in games which use rasters.

- Possible heat problem.

Being able to hit a switch so one could swap between both speeds would surely be the way to go until its confirmmed that no problem exist.

Raz

Hello,

I have an extra MVS unit and decided to overclock it out of curiosity. I looked at the Motorola Datasheet for the 68000 and found the Clock signal is on chip leg #15. It is the same chip leg for both the DIP and PLCC version. The modification was performed on a MV-1B.

For my modification, I used a pair of wire cutters and carefully cut part of the leg near the bottom of the motherboard. I then used a small screwdriver to gently lift the leg up. I then soldered a 14 pin dip socket to 5v, GND, and leg #15. This way I can change oscillators quickly. To make sure I had a clean clock signal I also used solid copper wire. The Oscillators I used were 14.32mhz, 16mhz, and 18 mhz.

Here are my results on only a few games:

14.32 Mhz: Only a few games run problem free.

16 Mhz: Major Graphics corruption. Crosshatch screen garbled. Newer games with the special encryption chip won't boot (KOF 99 and Metal Slug 3). I would like to mention the corruption did not flicker for games that did boot.

18 Mhz: (Stopped Testing due to many errors at 16 mhz). The Neo Geo will still boot but the cross hatch corruption is even more severe.

Here is a subjective detailed report of what I noticed for the 14.32 mhz testing.

Metal Slug 1 (runs perfect)
Metal Slug X (runs perfect)
Metal Slug 3 (runs perfect)
KOF 94 (runs 99% perfect, sometimes the Neo Geo boot up logo has a small glitch)
KOF 98 (runs 99% perfect, sometimes the Neo Geo boot up logo has a small glitch)
KOF 99 (runs perfect)

Puzzle Bobble: Has a large section of graphics missing in bottom right hand corner. It is a rectangular black bar.
Last Blade 1: Occasionally characters will flicker and dissapear quickly
Last Blade 2: Occasionally characters will flicker and dissapear quickly. After the round is finished with the character victory screen, a part
of the background is missing (large black square)
Blazing Star: Major graphics corruption. Black squares and flickering squares of garbled data.
Kabuki Klash: Flickering squares of garbled data.
League Bowling: Flickering squares of garbled data.

The good news is that Metal Slug will run problem free ( I beat the games all the way to the end since I couldn't stop lol). And yes, slowdown is reduced or even eliminated in some areas. But the fact is that most games have many problems.

I have emailed Razoola and here is what he had to say in an email:

"Yes this to me sounds like what I expect, the cpu is simply writing through the gfx port to fast for the gfx chip to get the data correctly.

There is probably a way to correct allot of this but I'm not sure how difficult it will be to do. One way would be to overclock the gfx hardware if possible. The other option is to have the cpu alter its speed. It could slow to 12mhz while inside the vblank and back up to 14mhz once the vblank is over. I'm not sure if that is possible though, the best option is to oclock the gfx hardware for sure if possible.

Basically all writes to the gfx RAM go through one port so this is what you would need to speed up for the gfx to correct itsself.

From what you are saying I think its not a CPU related problem, its more the CPU writing to the gfx hardware port to fast for the other side to pick up the data correctly. "

Any Neo Geo technical experts have any ideas? I was thinking the next thing I could try was changing the 24 mhz motherboard crystal to a 32mhz one and also using a 6mhz Oscillator to run back to the Z80.

I hope my experiment was an interesting read for everyone,

-Efini

EDIT: I never used a heatsink for the overclocking. The 68000 and the motherboard for the most part was still very cool to the touch after playing metal slug for an hour. I don't think heat is an issue.

Personally, I think placing the Z80 on a seperate clock signal from the M68k is a non-starter. They share the same clock signal, by design; games are (most likely) written to expect that syncronization and thus have no interal sync routines. I have no clue what the specific ramifications of that would be, it would depend on what each individual game pushed onto the Z80 to process. It wouldn't be good though...

There is another thing to consider too...

I know a lot about computer architecture, but not much yet about Neo-Geo, so if I'm wrong my apologies in advance.

(I believe) the Neo is an XIP-based system. Basically, because it has so little system RAM, the instructions in the game cartridge must be executed directly from the cartridge, not copied into RAM like a 'normal' computer system.

Where am I going with this? Access times. A 33% overclock could be playing havoc with those ROM chips, expecially when you're dealing with slow (1990s tech) access periods and a software that was optimized to maximize performance (CAS, RAS, tRAS, etc.). That would also explain why certain games run OK while others don't, since I think the individual games set the memory access specifications.

TerryMathews said:

Personally, I think placing the Z80 on a seperate clock signal from the M68k is a non-starter. They share the same clock signal, by design; games are (most likely) written to expect that syncronization and thus have no interal sync routines. I have no clue what the specific ramifications of that would be, it would depend on what each individual game pushed onto the Z80 to process. It wouldn't be good though...

There is another thing to consider too...

I know a lot about computer architecture, but not much yet about Neo-Geo, so if I'm wrong my apologies in advance.

(I believe) the Neo is an XIP-based system. Basically, because it has so little system RAM, the instructions in the game cartridge must be executed directly from the cartridge, not copied into RAM like a 'normal' computer system.

Where am I going with this? Access times. A 33% overclock could be playing havoc with those ROM chips, expecially when you're dealing with slow (1990s tech) access periods and a software that was optimized to maximize performance (CAS, RAS, tRAS, etc.). That would also explain why certain games run OK while others don't, since I think the individual games set the memory access specifications.

Click to expand...

In a way you are both right and wrong. Certinally while accessing data from the ROM cart it will not really gain from the overclock due to the access times, however the actual calculations the CPU does will. This is things like sprite collision, updating the screen etc.

Basically the NeoGeo cannot access the gfx RAM space directly to update the screen. Instead there are some ports that are used instead. Its the writing to these ports that I feel is causing the problem gfx problems at least. Ports are as follows;

0x3c0000 vidram offset to read from or write to.
0x3c0002 used to peek or poke (pointed to by 0x3c0000).
0x3c0004 modulo to increment vidram pointer once poked.

This is where the problem is I feel, depending on how the game writes and reads these address causes the gfx glitches when overclocking. Whats needed is to somehow speedup the gfx hardware in this area.

Raz

This is fascinating... I hope we see some more experimentation

If I understood right, the problem comes from the gfx hardware, not able to follow the speed of the CPU if you overclock it.
In the same time, Efini tells us that MS2 (he said MS but I think he referred to this game) was running smoothly with a 14,32 Mhz clock.
In this case it means that the gfx chip can cope with the amount of operations, even with a higher speed of CPU.

Does it mean that MS2 is not well programmed (optimized??) for the AES hardware?

Since a few people are interested in this mod, here are a few pictures I took using a 16 mhz Oscillator.

MV-1B motherboard with Oscillator:
http://i5.photobucket.com/albums/y184/efinidc/DSCN2954.jpg

Crosshatch screen at 16mhz:
http://i5.photobucket.com/albums/y184/efinidc/DSCN2973.jpg

Blazing Star graphics garbled at 16 mhz:
http://i5.photobucket.com/albums/y184/efinidc/DSCN2975.jpg
http://i5.photobucket.com/albums/y184/efinidc/DSCN2979.jpg
http://i5.photobucket.com/albums/y184/efinidc/DSCN2980.jpg

Metal Slug X error free at 16mhz:
http://i5.photobucket.com/albums/y184/efinidc/DSCN2982.jpg
http://i5.photobucket.com/albums/y184/efinidc/DSCN2984.jpg

Robert, I've tested Metal Slug 1, Metal Slug X and Metal Slug 3 all at 14.32 Mhz and they all run perfect. Metal Slug 1 and Metal Slug X will even run error free all the way up to 18 Mhz. Metal Slug 3 will not boot at 16 Mhz but I think it is possible to switch it up to 18 Mhz with a halt switch and cpu speed selector. (1 pin to the oscillator and 1 pin back to the motherboard's 12 Mhz clock.) I have not had a chance to test Metal Slug 2 since a friend is borrowing it.

I would like to note that the garbled graphics flicker very quickly. When I tried to pause the games with dip switch 8 to take pictures, the garbled graphics would dissapear. All the in-game pictures are taken unpaused.

Please hold the flames on the crappy pics please

That crosshatch screen certinally looks like the problem is related to data going to the gfx hardware to fast. I can change the way that draws in the unibios so it could confirm if it is simply pokeing to those ports to fast. I just had a quick look at the code that does it and I can see that they are already slowing it down even without a overclock so that pretty much confirms it I think. here is the code;


Notice the NOP's between each write to the port. I would thin simply adding abother NOP so there are 2 instead of 1 would fix the problem. This confirms that even at 12mhz the CPU can be to fast for the gfx hardware. Looking at it the problem may be related to the modulo.

Raz

Today I went to my friend's house and grabbed Metal Slug 2 back from him. This game is notorious for a lot of slowdown. I tested Metal Slug 2 at 18mhz. The game will run just fine and the only problem is the neo geo boot up logo.

For the most part, many areas of slow down are gone. One example I can think of off the top of my head is level 1 with the camel slug and shooting the arabians. However, I would like to point out that Metal Slug 2 has so much slowdown that even at 18mhz, it doesn't get rid of them all. There is still a lot of slowdown on the train stage on the box cars if there are too many grunts. There is still some slowdown (although noticably less bad) on the part where there are hovercrafts shooting missles towards you.

Hope this helps the curious people about speeding up Metal Slug 2

-Efini

Can you get a picture of the neogeo bootup logo you mention is currupt. Its also possible that getting faster RAM chips will help speed things up but Im not 100% sure.

Even is this oclock mod isnt 100% good Im sure that it even working with the MetalSlug games is enough for people to want to do it. I can certinally change the unibios to fix peoplems created by the bios (crosshatch for example). All you will need to do is make a switch to control the CPU speed on the side of the Neo. Would also be an idea to have the switch reset the Neo when speed is changed (use the 68k reset line).

Raz

I'm very interested in knowing if anyone has tried to mod a neo system/game with more RAM? I don't think the slower CPU is necissaraly causing the slowdown in MS and the other mentioned titles, it just seems like a makeshift workaround of the real problem at hand. Making the ROMS faster seems like it would require modding the cart pcbs and not the system pcb.

The games were designed for the amount of RAM the hardware has, and wouldn't take advantage of any additional RAM if it was available.

toodles said:

The games were designed for the amount of RAM the hardware has, and wouldn't take advantage of any additional RAM if it was available.

Click to expand...

Not just the games, but the address lines on the board itself are most likely not set up to address any more RAM than is there,

I just like to jump in and say you guys are tickling my fancy. This is far more interesting than video improvement. Keep it up!

I've been trying to get a picture of the garbled neo geo logo upon game boot up. However, it isn't always there. It is very occasional and as I mentioned previously, if I try to pause it with dip switch 8, the graphic error will dissapear. So taking this picture hasn't been easy.

I would like to explain the neo geo logo corruption that I do see. It is a vertical rectangle. It is always the same size and it looks like the static on a TV. This rectangle will appear in different parts of the Neo Geo logo and it is always the same size and color.

Again, hope this helps

-Efini