Problem with FPU 68882

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exxos
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Re: Problem with FPU 68882

Post by exxos »

@Badwolf all the FPUs are tested fully which are sold in my store. Happy to retest, but if they fail even once, they go in the bin. In fact all the chips I sell are tested. It's why some moan about the price of items, but after duds and taxes etc... But anyway, nothing suspect would make it into the store as I only want to sell chips which work.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
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Badwolf
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Re: Problem with FPU 68882

Post by Badwolf »

exxos wrote: Sun Oct 17, 2021 12:03 am @Badwolf all the FPUs are tested fully which are sold in my store. Happy to retest, but if they fail even once, they go in the bin. In fact all the chips I sell are tested. Its why some moan about the price of items, but after duds and taxes etc... But anyway, nothing suspect would make it into the store as I only want to sell chips which work.
@exxos I completely believe you and sorry -- I just realise how that could be read!

I wasn't accusing your chips -- far from it, there's a reason I get my chips from you -- I meant I don't trust that when I plug them in that they're going to behave, even though the chips are fine.

I've chips labelled as kaput in front of me here that, in desperation, I've put in and suddenly passed all the tests. All that business with the crappy sockets attests to it.

No, please don't take it that way. I meant if I had any confidence in being able to test them reliably I'd offer to, as a third party.

BW
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exxos
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Re: Problem with FPU 68882

Post by exxos »

@Badwolf no I didn't take any offense or anything.. I was more picking up on your offer to test. I didn't want to give the impression to anyone that I wouldn't retest if someone thought a chip was faulty. But also just emphasising that its unlikely as they are all tested :)
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
Roberto
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Re: Problem with FPU 68882

Post by Roberto »

exxos wrote: Sat Oct 16, 2021 11:46 pm As said before, the clock patch is probably to blame. It drives the FPU clock and the rest of the system. You seem to be getting ram corruption trying to use the FPU. The FPU test does not bomb, it shows errors. But bombs mean system corruption somewhere.as the FPU can't really corrupt ram , the common thing is the clock patch.
Thanks, I also think it's that clock patch. I am organizing to ship my new FPU 68882 to a guy here in Italy where he also has a Falcon, which works correctly with a 68882. So I am waiting for this test which can confirm what you say. Do you know what though? Now that I remember I have a RAM expansion that goes up to 14MB and I have never tried the 68882 without RAM expansion. As soon as I have some time I also do this last check, because as you say it could be the fault of the RAM (hoping that the problem is not in the part of RAM soldered into the motherboard of course ...). As for thorough software RAM testing (not the one we see at startup), do you have any ideas of what I could use?
Thank you so much!
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Re: Problem with FPU 68882

Post by Roberto »

Badwolf wrote: Sat Oct 16, 2021 11:52 pm Three bombs? Not seen that before with FPU.

Good work with the cleaning -- you've at least concentrated on the most likely and the simplest fix.

I'd offer to test your 68882 for you, but I've become so untrusting of that damned FPUs infrastructure*, I wouldn't be confident of being able to!

To be honest, at this stage, if you've got a 68881 that works, I'd stick with it. Count your blessings! They're a nightmare.

BW

*EDIT: that previously read 'of that damned chip'. That could have been read to unfairly cast aspersion on Exxos' chips. That was not my intention. I've come to the opinion that if you put a chip in that socket and get it working *never breathe on it again*!
Thanks for your help, I will send my FPU 68882 to a guy here in Italy who will carry out the test. This is a good idea as he has a 68882 FPU and it works correctly in his Falcon.
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Re: Problem with FPU 68882

Post by Roberto »

exxos wrote: Sat Oct 16, 2021 11:46 pm As said before, the clock patch is probably to blame. It drives the FPU clock and the rest of the system. You seem to be getting ram corruption trying to use the FPU. The FPU test does not bomb, it shows errors. But bombs mean system corruption somewhere.as the FPU can't really corrupt ram , the common thing is the clock patch.
Hi exxos,
I have seen you sell a very nice and clean patch compared to the one currently mounted on my Falcon. Do you think I could use yours instead of the one currently installed to have any chance of success in using the 68882?
I saw yours which is:
FALCON 030 CLOCK BUFFER PATCH V2 £ 16. 33 In Stock [0073]

and a video showing the very simple installation on:



I have already performed a thorough RAM test with a well-known German program, and it found no errors, so as you say, the problem probably lies in the current clock path.

Thanks!
Roberto
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Re: Problem with FPU 68882

Post by Roberto »

exxos wrote: Sat Oct 16, 2021 11:46 pm As said before, the clock patch is probably to blame. It drives the FPU clock and the rest of the system. You seem to be getting ram corruption trying to use the FPU. The FPU test does not bomb, it shows errors. But bombs mean system corruption somewhere.as the FPU can't really corrupt ram , the common thing is the clock patch.
I forgot, this is the revision of my Falcon 030:

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Steve
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Re: Problem with FPU 68882

Post by Steve »

@Roberto yes you can definitely use Exxos clock patch. Please just double check underneath the floppy drive area, photograph the large chip there (sdma) just to make sure there isn't anything else strange hanging about. It should be a fairly simple task to remove that old one and install the new one, ask if you get stuck.

Also see the yellow wire on your clock patch? That seems to be double soldered to both the R216 and R221 pads which feeds both the CPU and FPU clock (from memory) The Exxos patch has two dedicated clock outputs for each pad. That old clock patch looks like a poor version for sure.
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Re: Problem with FPU 68882

Post by PaulJ »

troed wrote: Thu Oct 14, 2021 9:44 am
PaulJ wrote: Thu Oct 14, 2021 1:06 am It would be my guess that a 68881 has a differient pal that the 68882. Just a guess.. When I put a 68882 in my MSTE from Exxos it needed a pal. Don't know about a falcon..
The MSTE needs one for FPU or no FPU - but that's very different from the Falcon going from one FPU to another. Also they're addressed differently, with the MSTE needing I/O mapping (the PAL) while the Falcon's 030 does the lifting itself (FPU instructions).

I run a 68882 in my Falcon without issues.C
You're absolutely right Troed, I was associating the issue with a MSTE. :oops: :oops: :oops:
Roberto
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Re: Problem with FPU 68882

Post by Roberto »

Badwolf wrote: Sat Oct 16, 2021 11:52 pm Three bombs? Not seen that before with FPU.

Good work with the cleaning -- you've at least concentrated on the most likely and the simplest fix.

I'd offer to test your 68882 for you, but I've become so untrusting of that damned FPUs infrastructure*, I wouldn't be confident of being able to!

To be honest, at this stage, if you've got a 68881 that works, I'd stick with it. Count your blessings! They're a nightmare.

BW

*EDIT: that previously read 'of that damned chip'. That could have been read to unfairly cast aspersion on Exxos' chips. That was not my intention. I've come to the opinion that if you put a chip in that socket and get it working *never breathe on it again*!

After some time I found the problem. I inspected (with the help of a needle), each track of the socket, soldered into the motherboard: that is, I tried to move the tracks with the needle. The last track to be tested .. bingo! It had jumped. So with a soldering iron I restored the contact ... now it works. Thanks to you Badwolf, and everyone who helped me.

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