Another semi-crazed thought

[LinkoVitch]

Since GazTee poluted my mind and I now HAVE to have a Co-Jag to go with my JAMMA collection.. I am looking at them on ebay...

 

A few thoughts tho... it looked like the Co-jag runs the Tom & Jerry chips at around 52MHz (speed of crystal on the board), so with some cleaver careful fiddling, perhaps we could clock a stock Jags Tom & Jerry to that speed, and somehow keep the 68K at it's 12.5 ish MHz ? Imagine Supercross 3D with a better framerate :) (more likley imagine 99% of jag games crashing.. but.. )

 

and then also.. as the Co-Jag is a touch faster... and better general CPU.. and an already present IDE interface.. how about whipping out the ROMs and using it as a jag based computer system? Theres a novel idea for you smile.gif

 

complete pie in the sky.. but it gets you thinking ... well it does me at 8am in the morning in a cold office

[Zerosquare]

A few thoughts tho... it looked like the Co-jag runs the Tom & Jerry chips at around 52MHz (speed of crystal on the board), so with some cleaver careful fiddling, perhaps we could clock a stock Jags Tom & Jerry to that speed, and somehow keep the 68K at it's 12.5 ish MHz ?

Don't you think Tom & Jerry are already buggy enough at their normal clock rate ?

 

Overclocking the Jag has already been evoked before, but one problem is that everything (video, audio, timers, RAM access times...) is tied to the same clock, so you'd have to patch existing software. Also, even if the Co-Jag uses the "same" chips, they're not necessarily manufactured using the same process, which has a major influence on the chip's maximum clock rate. If the stock Tom & Jerry could run at 52 MHz, I don't see why Atari wouldn't have done it (a 52 Mhz oscillator is not much more expensive than a 26 MHz one )

Edited November 1, 2006 by Zerosquare

[LinkoVitch]

Maybe if we get more bugs per second they will start canceling out ?

 

If I were to try this I would try and maintain as many of the low level clocks as possible (for screen sync and 68K etc), using dividers on the main clock, IE divide the 52 in half to get a 26 and then feed this into the original system after it has been disconnected from the parts that were trying to be run faster.. so Tom and Jerry.

 

Then sell the slightly charred remains on ebay

[justclaws]

Hi Linko,

Since GazTee poluted my mind and I now HAVE to have a Co-Jag to go with my JAMMA collection.. I am looking at them on ebay...

CoJags on Ebay? Wow. You sure they're no Kojaks? :-)

 

A few thoughts tho... it looked like the Co-jag runs the Tom & Jerry chips at around 52MHz (speed of crystal on the board), so with some cleaver careful fiddling, perhaps we could clock a stock Jags Tom & Jerry to that speed, and somehow keep the 68K at it's 12.5 ish MHz ? Imagine Supercross 3D with a better framerate :) (more likley imagine 99% of jag games crashing.. but.. )

That's an interesting thought, yes, as I believe 40Mhz was the original target clock speed.

The 52Mhz, that's astounding. Is it the same silicon as used on the Jag, or are they different versions?

 

I think a very interesting question is what is the RAM used on CoJag? Is it SRAM or DRAM, what speed?

I imagine SRAM with the Jag would eliminate the wait-states which make the GPU buggy would it not?

 

and then also.. as the Co-Jag is a touch faster... and better general CPU.. and an already present IDE interface.. how about whipping out the ROMs and using it as a jag based computer system? Theres a novel idea for you

Novel idea? Sacrilige! Rare kit must remain in it's original condition, sorry!

 

complete pie in the sky.. but it gets you thinking ... well it does me at 8am in the morning in a cold office

The thing to see done with some spare Tom/Jerry parts would be to put one (well a Tom) in a cartridge,

as a co-processor. The cart would have it's own RAM or Flash ROM (oh, yes, hello Compact Flash card!)

and the GPU would run code from it's own RAM uploaded via the Jag to render images for the main system

which would see it as ROM. That would be super-neat. No fancy co-processing connection required there!

 

Sadly although I've build accessory boards for M68K systems in the past, such a GPU board is beyond me!

 

Cheers,

JustClaws.

[LinkoVitch]

Hi Linko,

Since GazTee poluted my mind and I now HAVE to have a Co-Jag to go with my JAMMA collection.. I am looking at them on ebay...

CoJags on Ebay? Wow. You sure they're no Kojaks? :-)

 

Well that would explain why they come with lolly pops

 

A few thoughts tho... it looked like the Co-jag runs the Tom & Jerry chips at around 52MHz (speed of crystal on the board), so with some cleaver careful fiddling, perhaps we could clock a stock Jags Tom & Jerry to that speed, and somehow keep the 68K at it's 12.5 ish MHz ? Imagine Supercross 3D with a better framerate :) (more likley imagine 99% of jag games crashing.. but.. )

That's an interesting thought, yes, as I believe 40Mhz was the original target clock speed.

The 52Mhz, that's astounding. Is it the same silicon as used on the Jag, or are they different versions?

 

I think a very interesting question is what is the RAM used on CoJag? Is it SRAM or DRAM, what speed?

I imagine SRAM with the Jag would eliminate the wait-states which make the GPU buggy would it not?

 

One point that has been raised is that the clock could simply be for the alternate General CPU and simply divided down for the tom & Jerry, more investigation will be needed I think.. Oh dear this means I need to get a Co-jag for the good of science.. forshame!

 

I would imagine the RAM will be DRAM, as I recall the co-jag has a fair bit more than a jag and that much RAM as SRAM would not have been cheap.. Again I will look into this as soon as I can

 

and then also.. as the Co-Jag is a touch faster... and better general CPU.. and an already present IDE interface.. how about whipping out the ROMs and using it as a jag based computer system? Theres a novel idea for you

Novel idea? Sacrilige! Rare kit must remain in it's original condition, sorry!

 

no no no, it requires no modification! the replacement of the ROMs is essentially like changing the cart, they are even socketed! so just swap roms and plug in a different HDD, and we could run something else on it.. probably

 

complete pie in the sky.. but it gets you thinking ... well it does me at 8am in the morning in a cold office

The thing to see done with some spare Tom/Jerry parts would be to put one (well a Tom) in a cartridge,

as a co-processor. The cart would have it's own RAM or Flash ROM (oh, yes, hello Compact Flash card!)

and the GPU would run code from it's own RAM uploaded via the Jag to render images for the main system

which would see it as ROM. That would be super-neat. No fancy co-processing connection required there!

 

Sadly although I've build accessory boards for M68K systems in the past, such a GPU board is beyond me!

 

I have actually already been thinking along these lines in view to something similar to the superFX chip on the SNES. I agree would be a cool addon might make the cart a bit more pricey tho

[justclaws]

Hello,

I would imagine the RAM will be DRAM, as I recall the co-jag has a fair bit more than a jag and that much RAM as SRAM would not have been cheap.. Again I will look into this as soon as I can

I don't think expense is something which is such a big factor for an arcade board, so it could be SRAM.

However, the other possibility is of course that it's just faster DRAM I suppose. Any schematic around?

 

Cheers,

JustClaws.

[LinkoVitch]

Hello,

I would imagine the RAM will be DRAM, as I recall the co-jag has a fair bit more than a jag and that much RAM as SRAM would not have been cheap.. Again I will look into this as soon as I can

I don't think expense is something which is such a big factor for an arcade board, so it could be SRAM.

However, the other possibility is of course that it's just faster DRAM I suppose. Any schematic around?

 

TBH, I wouldn't say that was the case. The arcade boards I have (about 14 My collection on VAPS ) none of which are particularly OTT engeneering wise. Quite often just stock systems with a few tweaks, or masses of 7400 logic. I had a Tekken board and it litterally was just a PSX with no CD ROM, (I recognised it as I used to diddle around inside PSX's a fair bit )

 

Arcade boards are just consoles like everyone else... they just get a bad rap and treated differently Plus you want your hardware to be cheap so you can rake in the money from the game