Replacing Jag Hardware?

[82-T/A]

Hey guys,

 

Couple of things that just occured to me. I am considering buying World Tour Racing as I don't currently have it. Being an IndyCar and Formula-1 fan, I figured it's a game that I HAVE to have for the Jag.

 

I was reading this review about it from Keita on AtariHQ.Com

http://www.atarihq.com/reviews/jaguar/world_tour_racing.html

 

Basically, the game runs extremely slowly and the frame rate is rather poor. Similarly, I know that Fight For Life... although an excellent game, at SOME points does have a slight frame-rate issue.

 

What I was wondering is... does the Jaguar have any onboard memory? I know that the cartridges are 1, 2, 4, etc... meg cartridges, but does the Jag itself have any onboard memory for operating and transferring data across the bus (or whatever??)? And secondly, I know that the Jaguar has a 68000 Motorola chip. I know that this chip is SUPPOSED to just handle I/O stuff, but has anyone thought about maybe replacing this chip with a better one, like the 12Mhz MC68000. I really don't know that much about this stuff, but as I understand it these are backward compatible. Im my mind (without knowing the specifics), I'm under the impression that you could simply unsolder the old one and put this new one on. Is that possible? I know that this seems more realistic with any onboard memory there might be. Perhaps the ram on the Jaguar is 70ns??? We could replace it with nearly identical chips (same parity, etc...) that run at 60ns?

 

My question is... would this at ALL be beneficial to the jaguar, and would it speed things up like video reproduction. And, would replacing the 68000 cause games to run to fast or is the clock speed handled by something completely different?

 

 

Thanks!!!

[JagFan422]

this is a jag cd game, not a cart game, so i'm not sure what makes up the cd unit and what it adds to the base unit, but i didn't know if you factored that into your questions or not.

[doctorclu]

My question is... would this at ALL be beneficial to the jaguar, and would it speed things up like video reproduction. And, would replacing the 68000 cause games to run to fast or is the clock speed handled by something completely different?

 

You know what has always confused me is when you talk about the 68K chip, I have seen many varients of the 68K from a rectangular chip about three inches long (like in the ST and early Macs) to one that looks like a one inch by one inch math co processor (which I think the Jaguar has).

 

That said, I have been tempted at times to look into the AdSpeed ST and other processor accelorators for others machines and see if this couldn't be applied to the 68K on the Jaguar with a speed switch.

 

My favorite Processor doubler was the AdSpeed ST that boosted an ST from 8 mhz to 16 mhz. Nice! Made some games play better and definately made net surfing a bit more tolerable.

[+Stephen Moss]

The Jag as 2 Meg of internal RAM on the main PCB however as both the RAM and processors are surface mount devices replacing them is so not an easy thing to do without the right equipment and experiance if you want to leave the PCB in a useable state, also to make such an upgrade availabe to all owners would probably require new main PCBs to be designed and built. I addition to this although it is difficult to tell due to the poor quality of the online schematics I don't believe that there are any spare addresses for increasing the size of the RAM.

IIRC one or two people have changed the crystals in their Jags to increase the clock speed but it causes timing issues with some software.

 

As for WTR the controls are rather poor, an analogue controller my have provided a better control input, I am not expert at assessing frame rate but I though it was ok although I have not played it as much as I would have liked as the detail in the constantly changing background makes me ill. A more basic background such as that in Microprose F1 would have suited me much better and probably increased the frame rate as less processing would have been required but then people would probably complain that it was to 16 bit and not making good use of the Jags abilities.

[82-T/A]

The Jag as 2 Meg of internal RAM on the main PCB however as both the RAM and processors are surface mount devices replacing them is so not an easy thing to do without the right equipment and experiance if you want to leave the PCB in a useable state, also to make such an upgrade availabe to all owners would probably require new main PCBs to be designed and built. I addition to this although it is difficult to tell due to the poor quality of the online schematics I don't believe that there are any spare addresses for increasing the size of the RAM.

IIRC one or two people have changed the crystals in their Jags to increase the clock speed but it causes timing issues with some software.

 

As for WTR the controls are rather poor, an analogue controller my have provided a better control input, I am not expert at assessing frame rate but I though it was ok although I have not played it as much as I would have liked as the detail in the constantly changing background makes me ill. A more basic background such as that in Microprose F1 would have suited me much better and probably increased the frame rate as less processing would have been required but then people would probably complain that it was to 16 bit and not making good use of the Jags abilities.

 

Thanks Stephen, I wasn't really planning on increasing the ram, but actually replacing the ram with chips that are faster. You know, like 60ns chips as apposed to 70. My guess is that they're probably 60ns chips and I think even something at 50ns would be a significant improvement in data to and from the memory. This in particular would not affect the clock speed, but would in fact make loading times a bit shorter.

 

However, you mention that the clock speed is handled by something else... this tells me that replacing the 68000 WOULD in fact be possible so long as the new chip is backward compatible.

 

I'm going to buy a couple of spare and broken jags off eBay and take them apart.

[JagFan422]

again i'm going to ask, as this sounds very interesting and if it was possible to mod the jag to speed up the frame rate, then this could certainly help alot of the games.

 

But the game you mention is a CD game, not a cart. I'm not expert on the Jag or Jag CD, but wouldn't something in the CD unit have to be messed with? How much of the actual Jag hardware does the CD unit use?

[Orion_]

stop dreaming, the Jag is not a PC hardware, first the current 68000 in the Jag is exactly the frequency of the GPU/DSP divided by 2, 27Mhz -> 13.5Mhz

so it's faster than the 12Mhz you want to put

and a 3D game like that don't use the 68k, because the 68k is slowing everything on the jaguar, it use the GPU and blitter, that are very fast !

the problem is, you can't overclock the frequency of the GPU because it will depend of the DSP frequency and 68k frequency (there is only one crystal for everything If I remmember, for cost reason)

and GPU/DSP timming are not known, so I think it's impossible. replacing the RAM is also impossible because those chip are obsolete and not produced anymore ....

Edited May 26, 2006 by Orion_

[82-T/A]

again i'm going to ask, as this sounds very interesting and if it was possible to mod the jag to speed up the frame rate, then this could certainly help alot of the games.

 

But the game you mention is a CD game, not a cart. I'm not expert on the Jag or Jag CD, but wouldn't something in the CD unit have to be messed with? How much of the actual Jag hardware does the CD unit use?

 

 

I don't REALLY know the answer to this, but if I had to guess, I'd say that the ONLY thing the CD unit does is actually provide data into a readable format for the Jaguar. I'm almost positive that the Jaguar unit itself STILL does all of the processing and manipulation of the data. I think the JagCD is ONLY a CD Drive, and nothing else (except maybe housing the VLM).

 

 

stop dreaming, the Jag is not a PC hardware, first the current 68000 in the Jag is exactly the frequency of the GPU/DSP divided by 2, 27Mhz -> 13.5Mhz

so it's faster than the 12Mhz you want to put and a 3D game like that don't use the 68k, because the 68k is slowing everything on the jaguar, it use the GPU and blitter, that are very fast ! the problem is, you can't overclock the frequency of the GPU because it will depend of the DSP frequency and 68k frequency (there is only one crystal for everything If I remmember, for cost reason) and GPU/DSP timming are not known, so I think it's impossible. replacing the RAM is also impossible because those chip are obsolete and not produced anymore ....

 

 

Truth be told, I was really more concerned with the RAM than I was the processor. The processor was more of an "in addition" thing to my thoughts on this than anything else.

However, you might not be 100% correct on that. MANY old chips, ram and otherwise, are still produced. If you look in the back of a Scientific American, you can still buy 8088 processors with crazy speeds of like 800 to 1,500 Mhz. (seriously). That said, even if they DID stop making those specific ram chips, it's still more than likely that there is a large number of them produced and stored somewhere. Typically they make more components for spare parts and warranty repair. These ram chips were not made specifically for the Jaguar, I can almost guarantee that to you. I'm sure they're regular DRAM chips that were used on many many other applications. More often than not, the DRAMS are available on SIMMS, and you just have to remove them from the board.

 

I've got three spare jaguars coming to my house in the mail. When I get them, I'm going to take them apart and see just how difficult it will be to remove the old memory DRAMs and put them on.

 

Specifically, I'm hoping that by replacing the ram chips with faster ones will in fact speed up frame rates of various games. Usually (and I say this as a programmer, not as an expert on the jag), when you write software or develop graphics for a game, it usually goes from the media it's stored on, into memory, where it then goes to the processor. The ram is a necessary middle man, and by replacing it with faster chips, it SHOULD run quicker while not affecting anything else.

 

At the time the Jaguar came out, memory was really expensive. I mean, when did it come out... like in 1993? In 1993, 4mbs of ram would cost you well over $300 dollars. And that was for four 1mb 32pin SIMM, parity memory sticks.

 

So... in terms of speed... a set of 60ns ram chips were significantly more expensive than a set of 70ns chips (or even 80). If you had 60ns chips back in those days, you were screaming. Most people opted for the 70ns chips which were significantly better than the 80ns that was primarily standard. My guess is that IBM had to cut their costs where they could when building the Jaguars.

[SCPCD]

Hi !

 

Specifically, I'm hoping that by replacing the ram chips with faster ones will in fact speed up frame rates of various games. Usually (and I say this as a programmer, not as an expert on the jag), when you write software or develop graphics for a game, it usually goes from the media it's stored on, into memory, where it then goes to the processor. The ram is a necessary middle man, and by replacing it with faster chips, it SHOULD run quicker while not affecting anything else.

 

This is only true if the dram controler can use the DRAM at higher speed.

On the Jag it is not true.

The DRAM on the jag is used at the highest speed that TOM could control it.

So replace DRAM at 70ns by 60ns or 50ns don't increase the speed of games if you don't increase the TOM clock.

But increase TOM clock could made the system very unstable because all clock registers are not properly initialised (videos registers, and others) at the boot or at game initialisation.

The last bad point is that we have no informations about the TOM and Jerry timings so increase frequency could crash TOM and/or Jerry where I think that TOM and Jerry are not very tolerent on higher speed.

 

Regards,

SCPCD.

[82-T/A]

Hi !

 

Specifically, I'm hoping that by replacing the ram chips with faster ones will in fact speed up frame rates of various games. Usually (and I say this as a programmer, not as an expert on the jag), when you write software or develop graphics for a game, it usually goes from the media it's stored on, into memory, where it then goes to the processor. The ram is a necessary middle man, and by replacing it with faster chips, it SHOULD run quicker while not affecting anything else.

 

This is only true if the dram controler can use the DRAM at higher speed.

On the Jag it is not true.

The DRAM on the jag is used at the highest speed that TOM could control it.

So replace DRAM at 70ns by 60ns or 50ns don't increase the speed of games if you don't increase the TOM clock.

But increase TOM clock could made the system very unstable because all clock registers are not properly initialised (videos registers, and others) at the boot or at game initialisation.

The last bad point is that we have no informations about the TOM and Jerry timings so increase frequency could crash TOM and/or Jerry where I think that TOM and Jerry are not very tolerent on higher speed.

 

Regards,

SCPCD.

 

 

Thanks, I didn't realized the speed of the ram was so involved.

 

I've already paid for some spare "loose" Jaguars... so I might as well give it a shot and see what happens.

 

 

Thanks for the information...

[Isgoed]

Yes, give it a shot.

 

Maybe you'll achieve some surprising results, keep us informed

[Wilbur McCalmont]

Thanks, I didn't realized the speed of the ram was so involved.

 

I've already paid for some spare "loose" Jaguars... so I might as well give it a shot and see what happens.

 

 

Thanks for the information...

 

Unfortunately there is really nothing that can be done to increase the speed/performance of a stock JAG without causing it to become unstable or a fire hazard.

 

Increasing the clock speed on TOM or JERRY would cause the video to go out of sync, the sound to change in pitch (imagine the predator in AVP just before laughing inhaling from a helium balloon) and cause them to run hotter.

 

An engineering rule of thumb for digital logic is to use the slowest components that meet the design specs. This is because a faster component's quicker switching speed will induce more noise into a system with higher amplitudes that may cause unwanted level switching. So replacing the stock 80ns DRAM (some may have 70ns) with faster 50ns DRAM wouldn't increase the performance (you'd still have to increase the clock anyway), instead it may actually induce noise onto the video signal.

 

Also the DRAM used in the JAG is not of the common type found in normal 72-pin SIMMs - the 256K x 16 or 1-MEG x 16 parts have 2-CAS's while the JAG parts have 2-WE's. The JAG DRAMs are kinda' easy to find - you can find the exact parts or equivalents on ebay right now. However, finding the 50ns speed grade in the quantity you want and price you're willing to pay may impossible.

 

And even if you were able to successfully increase the overall speed of the JAG you would need to reverse engineer the games (the software) and change the appropriate variables in the code for the video, sound, game physics etc...

 

Although well intentioned I would recommend against overclocking the JAG or trying to increase it's performance other than passive mod's like a PAL/NTSC switch, S-VIDEO & COMPOSITE jacks, ROM switch, a bridge rectifier on the power input, or screen printing an image of a 3-eyed Lance corporal Lewis on the case, for example. If anyone still feels the need for more speed they should invest in a fire extinguisher and new batteries for their smoke detector before getting started.

[ZylonBane]

What I was wondering is... does the Jaguar have any onboard memory?

This entire thread should have died burning and screaming at precisely this point. It's like someone who claims to be a mechanic asking if a car has wheels.

[82-T/A]

What I was wondering is... does the Jaguar have any onboard memory?

This entire thread should have died burning and screaming at precisely this point. It's like someone who claims to be a mechanic asking if a car has wheels.

 

 

That was kind of an ass-hole response. Why did you feel it necessary to respond like that?

 

I've never once claimed to be an electrical engineer, so I'm not sure why you felt it necessary to suggest that I was being arrogant and thought I knew what I was talking about.

[+Stephen Moss]

Although well intentioned I would recommend against overclocking the JAG or trying to increase it's performance other than passive mod's like a PAL/NTSC switch, S-VIDEO & COMPOSITE jacks, ROM switch, a bridge rectifier on the power input,

As the Jaguer PSU provides a regulated DC output what would be the point in adding a rectifier?

[Zerosquare]

As the Jaguer PSU provides a regulated DC output what would be the point in adding a rectifier?

I guess not frying your Jag in case you accidentally plug in the wrong PSU ; the outer shell of the plug is positive, which is not common.

[Wilbur McCalmont]

Although well intentioned I would recommend against overclocking the JAG or trying to increase it's performance other than passive mod's like a PAL/NTSC switch, S-VIDEO & COMPOSITE jacks, ROM switch, a bridge rectifier on the power input,

As the Jaguar PSU provides a regulated DC output what would be the point in adding a rectifier?

 

 

As the Jaguer PSU provides a regulated DC output what would be the point in adding a rectifier?

I guess not frying your Jag in case you accidentally plug in the wrong PSU ; the outer shell of the plug is positive, which is not common.

 

It was a response to several old threads where a rash of people fried their JAGs when they plugged the wrong PSU into the JAG - namely the NES adaptor that had an A/C output voltage if I recall correctly.

 

Some of the threads:

 

Fried Atari Jaguar, help needed.

 

Burned out my Jag!

 

I toasted a JAG last night

 

No...my Jag...is dead.

 

The following topic by Punisher5.0 was either a "pinned" or "sticky" topic some time ago:

 

Jaguar fix when wrong polarity PSU is used+more

 

 

.

[+Stephen Moss]

As the Jaguer PSU provides a regulated DC output what would be the point in adding a rectifier?

I guess not frying your Jag in case you accidentally plug in the wrong PSU ; the outer shell of the plug is positive, which is not common.

 

It was a response to several old threads where a rash of people fried their JAGs when they plugged the wrong PSU into the JAG - namely the NES adaptor that had an A/C output voltage if I recall correctly.

 

I posted to some of those myself suggesting that labeling the PSUs was the answer. The problem with adding a bridge is that when you connect the correct PSU you will drop 1.4 volts across the bridge leaving the Jag with 7.6 volts, a 5 volt regualtor really needs a minimum of 8 volts input to regulate correctly as I doubt low drop out regulators were used.

Edited May 30, 2006 by Stephen Moss