68881 co-processor

[Gunstar]

I just installed the 68881 math co-processor in my Mega STE. I got it from B&C and it includes the needed PAL chip and instruction for $30. Anyway, I've tried it out with Cybersculpt and Phoenix object renderer and the speed increase in these polygonal environments is quite impressive. Phoenix is also designed to use the 68882 co-processor for the TT/Falcon and ST's upgraded with 68030 boards with the 68882 as well (two versions of the program). I wish the STE was designed for the 68882 as it's even better, but I'm happy with the upgrade. I recommend it to anyone who uses the STE for CAD programs (Like Jaguar developers). Good stuff.

 

I was wondering if anyone knows of any polygonal games that use the 68881 or 68882 if available to increase their speed as well. I specifically bought it for CAD, but if I can use it with some games that would be cool too.

[ijor]

I wish the STE was designed for the 68882 as it's even better, but I'm happy with the upgrade.

 

There was some talk recently on atari-forum about this (68881 vs. 68882). The concensus (more or less) is that you can use a 68882, but some older software won't detect it.

[Gunstar]

I wish the STE was designed for the 68882 as it's even better, but I'm happy with the upgrade.

 

There was some talk recently on atari-forum about this (68881 vs. 68882). The concensus (more or less) is that you can use a 68882, but some older software won't detect it.

943430[/snapback]

 

Then possibly Phoenix would work with the 68882 in the MSTE since it has two programs, one designed for the 68881 and one for the 68882. For now I'll settle with the 68881, since I just got it, but I may pick up a 68882 in a few months and see. Thanks for the heads up. Also, where exactly might the "cut-off" point be between "older" and "newer" software? It's all at least a dozen years old as far as I can tell.

[ijor]

Also, where exactly might the "cut-off" point be between "older" and "newer" software? It's all at least a dozen years old as far as I can tell.

 

I guess it should roughly coincide with the release date of the 68882. I don’t know that date but it shouldn’t be difficult to find it online. Add a couple or so months since the release until the new chip was actually tested on ST systems and the incompatibility was realized.

[Nick Harlow]

Also, where exactly might the "cut-off" point be between "older" and "newer" software? It's all at least a dozen years old as far as I can tell.

 

I guess it should roughly coincide with the release date of the 68882. I don’t know that date but it shouldn’t be difficult to find it online. Add a couple or so months since the release until the new chip was actually tested on ST systems and the incompatibility was realized.

943466[/snapback]

 

 

As someone who used Phoenix alot or Xenomorph as it is also known... I thought the '82 could be usedand would automaticaly be detectd.... it was on my Falc and TT

 

 

could be wrong tho, i will double check

 

nick

[Gunstar]

Also, where exactly might the "cut-off" point be between "older" and "newer" software? It's all at least a dozen years old as far as I can tell.

 

I guess it should roughly coincide with the release date of the 68882. I don’t know that date but it shouldn’t be difficult to find it online. Add a couple or so months since the release until the new chip was actually tested on ST systems and the incompatibility was realized.

943466[/snapback]

 

 

As someone who used Phoenix alot or Xenomorph as it is also known... I thought the '82 could be usedand would automaticaly be detectd.... it was on my Falc and TT

 

 

could be wrong tho, i will double check

 

nick

946112[/snapback]

 

Phoenix has two versions on the disk, one that uses the '81 and one that uses the '82, but cybersculpt and/or CAD 3D are needed with Pheonix (unless you are using the whole Phase-4 system instead of cyberstudio, I'm guessing) and both of them only support the '81, so if you have an '82 Phoenix can take advantage of it, but when you switch to Cybersculpt or CAD 3D (2.0) it won't be recogonized or used, but if you use the '81 then it works with all three, but of course Phoenix is faster with the '82 from my understanding (obviously I don't have '82 to know for sure).

Edited October 11, 2005 by Gunstar

[Gunstar]

I wish the STE was designed for the 68882 as it's even better, but I'm happy with the upgrade.

 

There was some talk recently on atari-forum about this (68881 vs. 68882). The concensus (more or less) is that you can use a 68882, but some older software won't detect it.

943430[/snapback]

 

yes, the '82 can be used in the MSTE as I understand it now, but only the Phase-4 system can use it (Phoenix, Rosetta, Chronos 3D, ?), If you use Cyberstudio like me, along with Phoenix only, then you are stuck with the '81. Obviously having either is better than none.

Edited October 11, 2005 by Gunstar

[krupkaj]

it is interesting. Do sombody know how it work with Falcon or TT where is 82 installed? I know it is possible to use 81 in Falcon but I am not sure how it works

[Greenious]

it is interesting. Do sombody know how it work with Falcon or TT where is 82 installed? I know it is possible to use 81 in Falcon but I am not sure how it works

947138[/snapback]

 

In F030 & TT, the FPU works as a co-processor, and in that respect, the 68881 & 68882 is 100% compatible. (Although 68882 is 50% faster than 68881)

 

In ST/STE, the FPU is a memory mapped peripheral unit. And that's what's causing the incompatibility. When they are memory mapped, they differ, and software written specifically for 68881, will not work with 68882.

 

So, if you got a 68881 in your TT or F030, get a 68882, it will not in any way cause you any problems, quite the opposite, since you will gain 50% speed.

 

I'm not 100% sure, but on ST/STE, I think software written for 68882 will work on a machine with 68881, but not the other way around.

 

Anyway, ST/STE owners will be more happy with that 68881 FPU, than you will be with it in a TT/F030.

[Gunstar]

Oh the irony! (becuase I thought I had a 68881 and was thinking about why I didn't get a 68882) Well, I was having some problems with some of my Cyberstudio software that I didn't have before installation of the FPU, and though I'm good with electronics and the installation was a breeze, even for a novice, I opened up my MSTE to check things out again, and low and behold, I had installed a 68882 FPU! I had just assumed it to be the 68881; the B&C catalog just said Mega STE FPU co-processor, and I naturally assumed it was the 68881 since it was only $30 and the 68882 is listed elsewhere at the B&C site for over twice that price! But it was the 68882&PAL chip that Bruce sent me! The installation instructions just say "mega ste co-processor." So, anyway, as part of the installation, there is this resister that was attached to the underside of the motherboard where the PAL chip socket is, this needed to be removed in the installation, so, now I can use the version of Phoenix made for the 68882, which is good, but the cyberstudio programs don't seem to like the 68882 very much, so I'm going to re-install the resister, with a SPST switch on it to turn the 68882 on and off depending on which programs I'm using...for now anyway (I don't know if something this simple will work or not, it's just an initial idea, anyone think it might cause problems to PAL chip installed? I haven't studied what pins the resister was actually joining on the socket yet, my guess would be something like the VCC&ground off hand) I may get a 68881 later for full compatibilty. Kinda funny how I never even bothered to look at the numbers on the fpu the first time I installed it...

Edited October 16, 2005 by Gunstar

[krupkaj]

I thought something like that.

 

So that means the Cyberstudio cannot use the FPU in my TT because it expects memory mapped one. Are there apps from Cyberstudio which can take benefit from TT's 68882?

[Greenious]

I thought something like that.

 

So that means the Cyberstudio cannot use the FPU in my TT because it expects memory mapped one. Are there apps from Cyberstudio which can take benefit from TT's 68882?

949185[/snapback]

 

If you use a program written for 68000 it will not be able to use the FPU on a 68030 machine, because in co-pro mode, the instructions for the FPU is incorporated in the 68030 code. ie, the FPU looks more or less like it is part of the CPU.

 

So, basically, what happens when the FPU is fitted in a TT or F030, is that your CPU gets a few extra instructions you can use.

 

On ST/STE, you get a few more memory adresses you can poke around with.

 

Gunstar, that resistor you talk about... Never heard you had to remove that to fit a FPU, you think you can type up those instructions for me to read?

[Gunstar]

I thought something like that.

 

So that means the Cyberstudio cannot use the FPU in my TT because it expects memory mapped one. Are there apps from Cyberstudio which can take benefit from TT's 68882?

949185[/snapback]

 

If you use a program written for 68000 it will not be able to use the FPU on a 68030 machine, because in co-pro mode, the instructions for the FPU is incorporated in the 68030 code. ie, the FPU looks more or less like it is part of the CPU.

 

So, basically, what happens when the FPU is fitted in a TT or F030, is that your CPU gets a few extra instructions you can use.

 

On ST/STE, you get a few more memory adresses you can poke around with.

 

Gunstar, that resistor you talk about... Never heard you had to remove that to fit a FPU, you think you can type up those instructions for me to read?

949246[/snapback]

I can if you want, but I can give you a more "precise" jist of it; It states that there is a jumper to be moved on, I believe, W1. But then in parenthesis it says that some motherboards don't have the jumper, so you have to turn the MB over and clip off the resister soldered across two pins on the PAL chip's socket, the only component on the bottom side of the board (true), when installing the PAL chip.

 

My MSTE is in the latter catagory. There is no WI or jumper at all on mine, and the resister was there, crossing kitty-corner on the last pins (which is why I naturally assume it's probably the VCC&ground. I hadn't looked for the dot or other to specify pin 1.

Edited October 16, 2005 by Gunstar

[Gunstar]

I think I've been sold the wrong type of FPU for the Mega STE, the chip is a MC68882FN33A version, and I was looking up info on the 68881 and 68882 chips and the particular one I have is stated to be a 33-50mhz chip. Shouldn't I have a 16mhz version that is the same speed as my 68000? I started doing the research becuase after discovering that it was a 68882 instead of 68881 chip, I attempted to load the 68882 version of the Phoenix Object renderer and it crashes with about a dozen bombs. I specifically ordered the catalog number from B&C that stated the MegaSTE co-processor, but the instructions I was given, while indeed instructions for installation on a Mega STE, look xeroxed too me and i'm wondering if B&C is just putting together these kits using copies of documentation and Bruce accidentally shipped me the wrong chip, whether it was supposed to be a 68881 or 68882, but a 16mhz one instead of a 30-33mhz version. Would this make a difference? or should a faster chip still work? below are the tables I'm refering too:

 

---------------------------------------------------------------------------

]Floating Point Coprocessor Speeds: (KFLOPS)

------------------16 Mhz 20 Mhz 25 Mhz 33 Mhz 40 Mhz 50 M

MC68881----------160 192 240

MC68882---------------------------------264 352 422 528

MC68040--------------------------------3,500 4,662 5,600

---------------------------------------------------------------------------

 

This forum screws up the lay-out of this diagram.

 

this was found here: http://archive.comlab.ox.ac.uk/cards/m68kfaq8.html

Edited October 18, 2005 by Gunstar

[jens]

or should a faster chip still work?

Hi.

The mhz are the highest possible clockspeed for the chip if you don't want to overclock it.

Would be a nice one for my Falcon.

I'm not sure the Mega/STe can use the 68882 but there should be material on that somewhere on the net or in chips'n'chips, Doit or the Atari ST/TT Profibuch (German book on the ST-computer line except for the Falcon).