downgrade Q800 with lc040, should all software still work?

[skeenna]

Finally got around to pulling the full 040 CPU out of the quadra 800 to swap with an LC 630.

I want the lc630 to have increased performance of the full 040.

But I do not want to trash the Q800.

When I put the lc040 chip into the quadra 800, she booted fine. However, the date and time control panel, among other programs, would give me a bomb with the message A system error has occured "finder" bad f-line instruction.

has this ever happened to anyone putting an lc040 chip into a machine which originally was meant to have a full 040 chip?

I am using os 7.1.1

 

[TylerEss]

I've never tried putting a 68LC040 into a Mac that came without one, but since SANE checks for a physical FPU before dispatching FPU instrutions, you shouldn't, on paper, have any trouble with a swap like this.

If you had a spare drive, I'd try swapping that into the Quadra and doing a clean install. (the spare drive would ensure you don't nuke your existing data just to find out that it won't help. )

 

[Macbuk]

Last year i used an LC040 into quadra 700 motheboard succesfully.

I'm pretty sure the problem you experience will disappear with a fresh install.

 

[Unknown_K]

I would think the software was installed aware of the FPU and now freaks when it is not there.

 

[skeenna]

thanks for the replies. it gives me some hope. that the downgrade can be done.

os 7.1.1

For the record,

the software installed ran the lc040 machine okay with the lc040 chip in it.

The software installed ran the 040 machine (q800) okay with the 040 chip in it.

The software installed is not running parts of some programs properly in the 040 machine with the lc040 chip in it. (bad f-line instruction)

Having said all that, i am going to check if the lc040 chip is still working properly in the lc040 machine. who knows, maybe i zapped it somehow in the transfer.

 

[tomlee59]

I think Unknown_K might have the right answer -- if you have changed the hardware configuration after installing the OS, things can go awry. The installed software may look for the FPU just once, during the initial install. After finding it, it may make the assumption that it remains there, instead of wasting cycles rechecking every single time it undertakes a calculation.

So, you may have to reinstall the OS to get it to start behaving properly. I am not certain at all about this, but it seems reasonable.

 

[Unknown_K]

Best bet is to find another full 040/33 and have both machines with an FPU.

 

[skeenna]

Yay!

The clean install cleared up the problem.

so now the q800 runs with an lc040 under 7.1.1 properly.

So Thanks to everyone who suggested the correct solution.

 

[Quadraman]

I don't know why you would even keep using the LC chip when full 040's are so cheap these days. The performance boost can't be beat for the price. I replace every LC chip in every machine I get that has one.

 

[Flash!]

Good to hear you're up and running - I was going to say "do a fresh install" but everyone else beat me to it

It should be noted that *some* software will not work without a real FPU (I have a CAD program bombs without a real one for example). There is a Control Panel you can use to trick it into thinking it has a FPU (I think it's called Soft FPU ???) but this has mixed results.

 

[equill]

... I want the lc630 to have increased performance of the full 040.
But I do not want to trash the Q800. ...

Help is at hand, if you wish to have it.

de

 

[TylerEss]

Anything about "F-line instruction" is an FPU problem; all the instructions beginning with F are reserved for the FPU on 68k.

 

[skeenna]

Oh Cripes, now things are not working and I now have doubts that they temporarily were.

I have been working with two q800's half stripped side by side.

I now believe that I accidentally did the fresh install on the q800 with the full 040 fpu in it -- which then proceeded to work as it had already been working. (I thought it was the q800 with the lc040 therefore I reported success above.) This was done too late at night I suppose.

The next evening when I got back to taking a closer look at things I noticed the q800 with lc040 was actually not working properly and giving me those f-line errors. So, I tried to do a fresh install (7.1.1 US version) on the q800 with lc040 in it but the installer kept giving me some system error with restart as my only option. ( and i know the installer CD and CD drive are good, cause I just used them successfully the night before.)

I can't spend any more time on this so am abandoning this downgrade for now. I have put the full 040 back in the q800 which works again and will have to wait to upgrade the lc630 at some other time.

 

[madmax_2069]

you could install softFPU so the software thinks there is a FPU there so it wont freak out. before i bought my full 040 cpu for my P475 i ran softFPU and was able to run stuff that required a FPU , granted it ran slower than it would normally with the full FPU but nothing ever freaked out on me that required one

 

[Quadraman]

you could install softFPU so the software thinks there is a FPU there so it wont freak out. before i bought my full 040 cpu for my P475 i ran softFPU and was able to run stuff that required a FPU , granted it ran slower than it would normally with the full FPU but nothing ever freaked out on me that required one

Adding compatability is always nice, but in this case I question whether it is worth it. It kind of defeats the purpose of having an FPU, which is to generally speed things up, if you are running the FPU functions in software, which is slow. Full 040's can be bought with pocket change these days, so it is no longer cost effective to go with a software solution, even if you can get it free due to the lost productivity if this machine is intended to be a daily user.