Overclocked Jaguar

[Gunstar]

Why overclock the 68k? Why not just drop it completely and use the faster GPU?

The overclocking is to make games the games already made run faster. You can't drop the 68K when a game already requires it, only with new games that can be designed without it. I've sure you already understood this, but you obviously didn't understand WHY it's being overclocked. For CURRENT games. It's especially a cool idea for games like I-war, Hover Strike, Supercross 3D, and others which have notoriously low frame-rates. This overclocking will allow them to play a much better speeds, if you don't mind the changes it makes to music and sound. Why Zero5 was used as a benchmark when it's one of the Jaguar's faster games I don't know. They should have used a slower game.

[Gorf]

Why overclock the 68k? Why not just drop it completely and use the faster GPU?

The overclocking is to make games the games already made run faster. You can't drop the 68K when a game already requires it, only with new games that can be designed without it. I've sure you already understood this, but you obviously didn't understand WHY it's being overclocked. For CURRENT games. It's especially a cool idea for games like I-war, Hover Strike, Supercross 3D, and others which have notoriously low frame-rates. This overclocking will allow them to play a much better speeds, if you don't mind the changes it makes to music and sound. Why Zero5 was used as a benchmark when it's one of the Jaguar's faster games I don't know. They should have used a slower game.

 

Show me HoverStrike...Then I'll tell you if it is worht the effort or not...Neat hack but useless

to most Jag fans as most are not hackers to be able to do it.

[SCPCD]

Why Zero5 was used as a benchmark when it's one of the Jaguar's faster games I don't know. They should have used a slower game.

I use Zero5 as benchmark because on all my jaguar cartridge games, it's the only one game where there is a real improvement.

For 1 VBL games there is no improvement and it's normal, it's not possible to have higher frame rate than 1 VBL (but there is always the accelerate sounds)

For near 1 VBL games (like zero5) the improvement are important. For exemple : to have a frame rate refresh from 2 to 1 VBL give the game 2x faster.

For slower games the overclock gives the game smoother but it's not so important. It's like go from 12fps to 15fps.

 

So an overclock can help the jaggy where the game frame rate slow down during the game for a normal jaguar, and it's more interesting for near 1 VBL games. For other games it's almost useless.

 

To be more interesting, the overclock should be reach the 2x original jaguar clock but it's not commonplace.

[Gunstar]

Why Zero5 was used as a benchmark when it's one of the Jaguar's faster games I don't know. They should have used a slower game.

I use Zero5 as benchmark because on all my jaguar cartridge games, it's the only one game where there is a real improvement.

For 1 VBL games there is no improvement and it's normal, it's not possible to have higher frame rate than 1 VBL (but there is always the accelerate sounds)

For near 1 VBL games (like zero5) the improvement are important. For exemple : to have a frame rate refresh from 2 to 1 VBL give the game 2x faster.

For slower games the overclock gives the game smoother but it's not so important. It's like go from 12fps to 15fps.

 

So an overclock can help the jaggy where the game frame rate slow down during the game for a normal jaguar, and it's more interesting for near 1 VBL games. For other games it's almost useless.

 

To be more interesting, the overclock should be reach the 2x original jaguar clock but it's not commonplace.

I appreciate your attempting to explain this to me, but I have no idea what 1 VBL is, so I have no reference point. And, once that is explained, what games do you have that are NEAR 1 VBL, and do you know of others that you don't have that are NEAR 1VBL. Basically, Zero5 is plenty fast for me as stands, one of the Jag's higher frame-rate games. I'm interested in improveing the speed of HoverStrike, possibly I-war, Supercross 3D, Fight for Life, Checkered Flag, Club Drive, etc.

But if it can improve a game by just 2-3fps, like you said, 12-15fps, that's plenty for me, smoother is better, even if only a few frames. For example, World Tour Racing is improved probably by about 2-3fps when the textures on the track are left off as opposed to turning them on, but I can tell a WORLD of difference in the lag time of the controls, and see a slight difference in how smooth the game moves, so even if you don't think 2-3fps is significant, I do; with a game like Supercross 3D, that would be nearly DOUBLING the frame-rate!

Edited July 21, 2007 by Gunstar

[Zerosquare]

I appreciate your attempting to explain this to me, but I have no idea what 1 VBL is, so I have no reference point.

"1 VBL" means that a new frame is rendered every time the screen refreshes, i.e. the games runs at 60 fps (NTSC) or 50 fps (PAL). 2 VBL would be 30 (resp. 25) fps, etc.

 

even if you don't think 2-3fps is significant, I do; with a game like Supercross 3D, that would be nearly DOUBLING the frame-rate!

Unfortunately, the gain with overclocking is a percentage of the original framerate. So if the original game runs at 2 or 3 fps, maybe you'd get 3.5 fps on an overcloked Jag... Edited July 21, 2007 by Zerosquare

[Gorf]

Why Zero5 was used as a benchmark when it's one of the Jaguar's faster games I don't know. They should have used a slower game.

I use Zero5 as benchmark because on all my jaguar cartridge games, it's the only one game where there is a real improvement.

For 1 VBL games there is no improvement and it's normal, it's not possible to have higher frame rate than 1 VBL (but there is always the accelerate sounds)

For near 1 VBL games (like zero5) the improvement are important. For exemple : to have a frame rate refresh from 2 to 1 VBL give the game 2x faster.

For slower games the overclock gives the game smoother but it's not so important. It's like go from 12fps to 15fps.

 

So an overclock can help the jaggy where the game frame rate slow down during the game for a normal jaguar, and it's more interesting for near 1 VBL games. For other games it's almost useless.

 

To be more interesting, the overclock should be reach the 2x original jaguar clock but it's not commonplace.

 

You'd probably need hydrogen at that point. But This is what I suspected that the speed increase would really

only mean less slow down. To make TOm and Jerry rock and roll...it needs a new system design with a REAL host

processor, like anothe GPU with 16k internal cache and its own meg mem bus. The Tom and Jerry get 8 megs

and 4 megs respectively on thier own busses and a nice mutli port ram between them so they can communicate

semiphores. It would be killer even at the 26.59 mhz clock.

[doctorclu]

Starting to look this over... a Bubsy speedrun at 36 mhz. Maybe that will help me in beating my 47-49 minute time.

 

Was this switchable in game? At least acceleration might help get past the sequences between levels a bit faster.

[doctorclu]

Are there any instructions anywhere on overclocking Jaguars?

[kskunk]

Are there any instructions anywhere on overclocking Jaguars?

 

It's not like overclocking a PC. To do it, you have to be either very good or very brave with a soldering iron. I don't know the details, but the freely available Jaguar Technical Reference Manual PDF lists the pins on Tom and Jerry that control the various clocks. You would need to add a new, faster, oscillator for the main clock while preserving the 26.6MHz video clock.

 

If you have no idea what I just said, maybe SCPCD will sell you one.

 

- KS

[doctorclu]

Are there any instructions anywhere on overclocking Jaguars?

 

It's not like overclocking a PC. To do it, you have to be either very good or very brave with a soldering iron. I don't know the details, but the freely available Jaguar Technical Reference Manual PDF lists the pins on Tom and Jerry that control the various clocks. You would need to add a new, faster, oscillator for the main clock while preserving the 26.6MHz video clock.

 

If you have no idea what I just said, maybe SCPCD will sell you one.

 

- KS

 

Makes sense from what I read in the Jaguar technical manual, and if I don't hear from SCPCD I might have to get a junker Jaguar from ebay and try it.

 

Otherwise, sure, I'd be willing to buy such an upgrade from SCPCD or whoever. Sure the sound may go out, but then when I'm playing Bubsy I generally have some other CD playing at the time, so no big deal.

 

Just want to see if I can beat the game in under 30 minutes.

[Zerosquare]

SCPCD doesn't sell mods

 

kskunk's right, the trick is to separate the system clock from the video clock (they're tied together in the Jaguar), then connect the system clock input to a faster external oscillator. It's not recommended unless you're pretty comfortable with a soldering iron.

 

Anyways, for 2D games such as Bubsy, overclocking is not really interesting. Most 2D games already run at 50 (or 60) fps, so they won't get any smoother. And most of them also use the video clock for their timing, which means they won't get faster either. The only effect you'd notice in the end is faster/broken sound.

 

I have a copy of Bubsy, I'll lend it to SCPCD someday to see if it plays differently on his overclocked Jaguar.

Edited November 21, 2008 by Zerosquare

[doctorclu]

I have a copy of Bubsy, I'll lend it to SCPCD someday to see if it plays differently on his overclocked Jaguar.

 

Please do!!

 

You know, he should make a whole series of videos showing as many games as possible accelerated. Just to see if it would be worth making an accelerated Jaguar.

 

They have that video on YouTube with 50 games on the Jaguar. Make one that has 50 games accelerated. Show Bubsy of course, iWar, Hyperforce, Hoverstrike, Iron Soldier... as many games as you can pull out and try. Would be fascinating.

 

Zero5 was EXCELLENT to demo, but would like to see others.

[kevincal]

Yeah I seriously want to see some Jag games accelerrated. But I think maybe not so much as that Zero 5 video LOL.

[Gorf]

To properly overclock, you'd need to re-write the Jag boot code so that the video registers

are written new values to handle the new clock.

 

Yes you can do it like SCPCD did and seperate the clocks but to do it system wide you would

need to re-write the boot.

[Zerosquare]

Actually, that wouldn't be enough. You'd have to make the horizontal period last more cycles to due the faster video clock. Which means the timings registers would have to be set differently (not a problem, since they're set by the boot ROM), but HDB1/HDB2/HDE also, and those are set by the game ; so, the picture would be offset horizontally.

 

Additionally, since the video clock frequency is fixed and can only be divided by an integer number of cycles, and you can't change the number of pixels per line without breaking existing games, the pixels' aspect ratio would change : you'd get a narrower picture as well.

 

Or you could do nothing at all and find a VGA monitor able to cope with a faster horizontal frequency. But besides old Necs, they're hard to find.

Edited November 24, 2008 by Zerosquare

[Atari_Owl]

Was this ever tested with the JagCD? We never did hear

[Gorf]

Actually, that wouldn't be enough. You'd have to make the horizontal period last more cycles to due the faster video clock. Which means the timings registers would have to be set differently (not a problem, since they're set by the boot ROM), but HDB1/HDB2/HDE also, and those are set by the game ; so, the picture would be offset horizontally.

 

Additionally, since the video clock frequency is fixed and can only be divided by an integer number of cycles, and you can't change the number of pixels per line without breaking existing games, the pixels' aspect ratio would change : you'd get a narrower picture as well.

 

Or you could do nothing at all and find a VGA monitor able to cope with a faster horizontal frequency. But besides old Necs, they're hard to find.

 

 

Yes, that is what I meant by re-writting the BIOS as that is where all the video/timming regs are loaded.

I figured by saying BIOS that would be covered.

 

Most of todays TV and monitors can handle all sorts of frequencies. You would have trouble finding one that went that low.

I do have on of those old NEC's...awsome monitor for gamers.