FPU for the Classic II?

#1 Sat, 18 Apr 2015 - 00:33 68kMLA

I've seen many LC Cards with FPUs like Ethernet w/FPU and so - again, for the LC Series Macs. But is there one for the Classic II? I remember a big expansion slot on the right side of the board but never seen anything that would fit it. Could an FPU go in there?

#2 Sat, 18 Apr 2015 - 00:43 68kMLA

Yes, there is one.

Here is a post, sadly no pics.

https://68kmla.org/forums/index.php?/topic/19803-macintosh-classic-ii-fpu-math-card-picture/

#3 Sat, 18 Apr 2015 - 01:23 68kMLA

Thanks Unity! Too bad for no pics though. Awwww...

It should be a simple hack to build. Any takers?

#4 Sat, 18 Apr 2015 - 01:27 68kMLA

I wanna say there *might* have been a thread with pics and discussion on how easy it would be to make one. If I recall, the board was simple. Pretty much just an FPU. One could get the socket from extra RAM cards. I would suggest more searching. The thread I just mentioned was more recent, but I did not find it. Also I dont think it was an FPU board made by Apple in that case.

#5 Sat, 18 Apr 2015 - 02:00 68kMLA

I have a FastMath Classic II. It's an extremely simple card and I bet someone on here could build a replica very easily. The trick would be getting a connector to match the Classic II's slot, which is unique only to that machine.

#6 Sat, 18 Apr 2015 - 02:41 68kMLA

The slot for the fpu card is the same as the classic ram expansion slot.

So should be easy I think someone was trying last year to reverse engineer one.

#7 Sat, 18 Apr 2015 - 08:58 68kMLA

I got started on an, in hindsight perhaps overly ambitious, card that would have sockets for both FPU and ROM expansion. (The two expansions are more or less completely orthogonal, only sharing physical space.) I got a bit bogged down in trying to choose a PROM technology. Flash would be best, obviously, but is somewhat challenging because write access to the expansion slot is not supported, so fiddly schemes like reading from unlikely sequences of addresses that as a group encode the address and data to be stored are required. Worse, my clever plan to use traditional UV-erasable EPROMs and add complexity only after I got that working encountered challenges because very few of the usable sizes are still available enough to buy in quantity without having to pay shocking amounts per chip.

In short, I’m still working on it in theory, but due to time constraints it won’t happen soon.

#8 Sat, 18 Apr 2015 - 10:27 68kMLA

yup acutely you could take a 50 pin scsi cable and plug it right into the header there,, then cut the wires and solder them right to a fpu and you should be all set... i think a couple ceramic bypass caps might be used, but maybe just hook it up direct anyways, and should be fine.

#9 Thu, 23 Apr 2015 - 16:55 68kMLA

Bahh, A fpu in a classic II is as cool as one in a lcii. So not really cool at all. I guess it has bragging rights? But for something that was so crippled ... I dunno .. If some one wanted to kiss. And just make a pcb already.. Then. Might be catch a few sales. The rom part sounds kinda cool but realistically will need rob or Doug to step in, they are the pros for that .