Jag Mods

[+poobah]

After watching the 27+ pages of the "it's 1993, thread", I got to wondering what mods could actually be done to the Jag. I am not aware of any.

 

So, what mods...

0) Are currently available

1) Could easily be realized

 

I've been thinking a lot about the 68K, about replacing it or helping it out. Moving to a '20 would be nice, but squeezing all those extra pins in would be a nightmare. Perhaps adding some local cache memory (think MegaSTe, or the AdSpeed type accelerators). Lift the existing 68k, and replace with a small board containing a new 68k and some fast sram.

 

I'm sure that would break a lot of code, but it may also open some new dev avenues.

 

Thoughts?

[Zerosquare]

Existing hardware mods that I know of, and the difficulty level :

- adding a reset switch (easy)

- adding a 50 Hz/60 Hz switch (easy)

- adding a boot switch for using 2 or 4 different ROM images, such as BJL, Stubulator, etc. (easy)

- adding the support for analog controllers, on Jaguars which don't have it built-in (easy)

- adding A/V outputs (easy)

- overclocking the processors (medium)

- adding connectors to access the internal bus ; only useful to those who do hardware development or very low level code optimization (hard).

 

Possible hardware mods :

- extending the internal RAM to 4 or 8 megs (hard). I think SCPCD tried it several years ago, but it wasn't 100% functional IIRC.

 

An accelerator board would be hard, and I don't think piggy-backing on the 68000 place would suffice.

[WIZZARD77]

I know of people who install 68010 into Sega Genesis units. They are supposed to be about 10-15% faster at the same clock speed and are direct replacements for the 68000 pin for pin. Unfortunately they are hard to find. Here's some info:motorola 68010

Edited December 24, 2009 by WIZZARD77

[Zerosquare]

Unfortunately, the 68010 isn't 100% software-compatible with the 68000 ; some games don't run on Genesis which have had their processor replaced by a 68010. People who upgraded their Atari or Amiga computer with a 68010 back in the day also discovered that some software would no longer work.

 

It's also supposed to be faster only in some cases, not in general, and by a modest amount. It would still be an interesting experiment to try, however

Edited December 24, 2009 by Zerosquare

[+poobah]

Well, if your loops are unrolled, you wont see much improvement.

 

I think there is an instruction or two that they changed to supervisor mode, and that's what breaks stuff.

[+poobah]

An accelerator board would be hard, and I don't think piggy-backing on the 68000 place would suffice.

 

Yah, I haven't poked around in any of my jags yet, but you'd definitely need to remove the existing CPU, I'll guess that it is surface mounted, so a socket would be problematic. Have to be pretty fast SRAM also.

[Gorf]

An accelerator board would be hard, and I don't think piggy-backing on the 68000 place would suffice.

 

Yah, I haven't poked around in any of my jags yet, but you'd definitely need to remove the existing CPU, I'll guess that it is surface mounted, so a socket would be problematic. Have to be pretty fast SRAM also.

 

You'd need to do a lot more than just piggy back a chip. It would be better to redisign the Mother board

to add an 020...if you are going to bother, then use an 060 and be done with it.

[carmel_andrews]

I think an 060 is overdoing it a bit gorf

 

How about a jag equivalent to the VBXE (or failing that a revised version of the OCS of the Jaguar)

 

Or as suggested something like a souped up 68k (like those 16/32mhz accellerators for the ST etc)

[Gorf]

I think an 060 is overdoing it a bit gorf

 

How about a jag equivalent to the VBXE (or failing that a revised version of the OCS of the Jaguar)

 

Or as suggested something like a souped up 68k (like those 16/32mhz accellerators for the ST etc)

 

I think modding the Jag at all at this point in it's after life is over doing so if your going

to bother go for the gusto, since no matter what you do will no doubt break compatibility with

all the current software out there. NOt to mention those accellerators are all 020,030 ,040 and

060's anyway. There is no 32 MHZ versions of a 100% compatible 68k that I know of. And all the

ST soup ups also break compatibility. The Jag is such a strange beast as it is that what ever

you do will probably break any software running on it anyway.all new software will need to be

re-written for it. The worst of moding the Jag with a 68k based anything wont help it run any

faster since it will still choke the main bus so if you are looking to speed the machine up

a 68k based processor with no internal cache is not going to help much at all.

Edited December 26, 2009 by Gorf

[+poobah]

I think an 060 is overdoing it a bit gorf

 

How about a jag equivalent to the VBXE (or failing that a revised version of the OCS of the Jaguar)

 

Or as suggested something like a souped up 68k (like those 16/32mhz accellerators for the ST etc)

 

I think modding the Jag at all at this point in it's after life is over doing so if your going

to bother go for the gusto, since no matter what you do will no doubt break compatibility with

all the current software out there. NOt to mention those accellerators are all 020,030 ,040 and

060's anyway. There is no 32 MHZ versions of a 100% compatible 68k that I know of. And all the

ST soup ups also break compatibility. The Jag is such a strange beast as it is that what ever

you do will probably break any software running on it anyway.all new software will need to be

re-written for it. The worst of moding the Jag with a 68k based anything wont help it run any

faster since it will still choke the main bus so if you are looking to speed the machine up

a 68k based processor with no internal cache is not going to help much at all.

 

Right.

 

That was the idea behind sticking with the 68K and just putting cache ram between it and the bus. Disabling the cache gets you back to the stock configuration. Enabling it gets the 68k off the bus (somewhat). It's the same thing Atari did with the 68k in the MegaSTe.

 

The utility here is not a 68k speed bump, it is feeding it from local cache memory instead of fighting with Tom and Jerry for the bus.

 

It's reversible and at least potentially doable.

Edited December 26, 2009 by poobah