What is the purpose of the extra socket on a LCII MB?

[MarkS]

Right next to the CPU are holes for a 68-pin PLCC socket. I'm guessing this is for a 68881, but I cannot find any documentation about this phantom socket. Has any ever played around with this?

 

[bigD]

You're right, although it's really for a 68882.

I suppose there's no reason you couldn't put a 68881 in it, but a 68882 would be better.

 

[MarkS]

I just typed 68881. Of course a 68882 would be better. Now I just have to find a place that sells them in quantities less than 1000. You know, like one or maybe two.

Thanks for the fast reply.

 

[Mike Richardson]

Every now and then one will show up on eBay which is suitable for the socket.

I'm not sure if the LC II will actually use the FPU if you put a socket there. Remember it's that crippled design with the 16 bus and 32 bit CPU.

 

[equill]

If you wish for a quick 68882, betake yourself hither, with haste.

de

 

[MarkS]

The 68882 in the PGA package will not fit those holes. Those holes are for a PLCC socket. I'd have to find a 68882 in a PLCC package.

Thanks for the link though! Great source for older MC chips. I was hoping to get my hands on a 68040 or 060 for a robotics project.

 

[MarkS]

Every now and then one will show up on eBay which is suitable for the socket.
I'm not sure if the LC II will actually use the FPU if you put a socket there. Remember it's that crippled design with the 16 bus and 32 bit CPU.

Looking at the data sheet for the 68882, available from FreeScale, the '882 can be interfaced with an 8-bit, 16-bit or 32-bit bus and it even shows how. Heck, if you really wanted to, you could add an '882 to any classic Mac without one.

 

[LCGuy]

The LCII is definately capable of taking a 68882. Remember, you could get PDS cards for the LC and LCII that had a 68882 on 'em...Daystar made them. And most LC PDS ethernet cards had a socket for one.

 

[Mike Richardson]

The LCII is definately capable of taking a 68882. Remember, you could get PDS cards for the LC and LCII that had a 68882 on 'em...Daystar made them. And most LC PDS ethernet cards had a socket for one.

I thought that socket was for some ROM boot thing. I'll have to get a 68882 and put it in one of my PDS ethernet cards now.

 

[LCGuy]

It could be for some of them, but my MCiLC card's manual says that its for an FPU.

 

[tmtomh]

The cheapest way to get a 68882 FPU in the proper form factor: find an old Mac IIvx. No one wants them, and they're not considered collectible - you can get them for free if you look around.

The 68882 is soldered to the mobo - just slice it off with a utility knife, make sure none of the metal pins is sticking out from the ceramic core, and stick it in your LCII.

I've done this before and it works perfectly.

Best,

Matt

 

[Bunsen]

Or ask around here - someone might be putting a PDS card into an SE/30 and removing a socketed FPU

 

[Mike Richardson]

The cheapest way to get a 68882 FPU in the proper form factor: find an old Mac IIvx. No one wants them, and they're not considered collectible - you can get them for free if you look around.
The 68882 is soldered to the mobo - just slice it off with a utility knife, make sure none of the metal pins is sticking out from the ceramic core, and stick it in your LCII.

I've done this before and it works perfectly.

Best,

Matt

Does doing that destroy the IIvx at all?

 

[kreats]

I've had a similar problem.. but the lc550 requires a 33MHz 68882, which is less common.

 

[~tl]

The cheapest way to get a 68882 FPU in the proper form factor: find an old Mac IIvx. No one wants them, and they're not considered collectible - you can get them for free if you look around.
The 68882 is soldered to the mobo - just slice it off with a utility knife, make sure none of the metal pins is sticking out from the ceramic core, and stick it in your LCII.

I've done this before and it works perfectly.

Best,

Matt

Does doing that destroy the IIvx at all?

I presume it'd run, albeit without the FPU...