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Problems with installing a 387 FPU

B

boggit

Experienced Member
Joined
Jan 4, 2024
Messages
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I bought a [387 FPU] off Ebay for my new 386 system and was glad to find that it had arrived in my mailbox today.

However, when trying to place it in the slot of my motherboard, I can not get it to fit, no matter how much i try. It seems like it should work but like it is just ever so slightly off.

83EB3E8D-282F-465A-B421-8F378134FDD8.jpeg

Is this the wrong slot for this type of 387 co-processor?
 
Last edited:
It 'should' go in that way...

There should be 17 pins per side with the upper left (as in your photograph) with a corner of the package missing.

Dave
 
daver2 said:
It 'should' go in that way...

There should be 17 pins per side with the upper left (as in your photograph) with a corner of the package missing.

Dave
Click to expand...
Yes exactly. I looked closely to make sure the odd corner was facing the right direction. Whenever I try to push it down properly into the slot, I push a corner down too deep into it, with the rest of the FPU sticking up somewhat instead.
 
I think the trick is to apply an even pressure in the middle of the chip .. if you press one corner then you force the opposite corner out as you figured out already
 
Maybe try pushing it with a flat surface so it's even pressure across the chip?
 
Heh...two same posts at the same time :)
Sometimes plastics get slightly deformed, the socket looks skewed on the down right side slightly outwards. The corner definitely doesn't look near 90deg. Check if that part is problematic
 
I see! Good to know that it is supposed to work, at least. Would have been annoying if I had bought a completely incompatible FPU.
 
Zare said:
Heh...two same posts at the same time :)
Sometimes plastics get slightly deformed, the socket looks skewed on the down right side slightly outwards. The corner definitely doesn't look near 90deg. Check if that part is problematic
Click to expand...
Yeah, it is definitely skewed on that particular picture. I just wanted to show the chip with the socket.
 
Haha Zare, you are right! I think the skew is because of the pic angle. As I remember this construction is a real tight fit and can be a real pig to seat properly .. I think patience is the best virtue here!
 
If the orientation is correct, check to make sure the socket isn't cracked. Seen that many times at work where someone originally forced the PLCC in either 90° or 180° out, and wound up cracking the socket. Sometimes it's a little hard to see.
 
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