(The following description and commentary was written by Nathan Mates and is reproduced here with his permission. I am grateful for the opportunity to present this rare bit of the Apple II story.)
Thanks to Dean Nichols for finding such a creation from the bowels of Apple and sending it down to me. First off, some facts about this: As identified by the silkscreened writing, this is a ‘SUPER II (c) 1981′ motherboard, made by Apple Computer, Inc, credited to Walt Broedner and John Macphee. Thus, it’s a prototype board that never was fully produced.
Next, I plopped this motherboard in a scanner at work and got 90% of it.
Observations and technical comments
At a first glance, this is almost a //e motherboard. It’s got the 7 slots plus extended slot out near the processor, a MMU and IOU unit to simplify most of the 74xx logic of the ][+ motherboard, a 9-pin game port next to dual cassette ports, and what looks like 64K of RAM on the board. However, it looks _too_ clean to be a //e motherboard-- there's just too much wide open space. Also, all chips are socketed, but that's to be expected for a prototype.
As I have no case, power supply and ROMs for a ][+ or //e, I have no way of powering this up right now; the rest of this is my educated guesses based on my knowledge of Apple II hardware, and my ability to follow traces on the motherboard. I don't have a 74xx handbook, so I can't conclusively identify all of them, but that's not too much of a problem for now.
Starting with the processor, it's a 6502B, (2Mhz capable) identified with a 'S' logo and 8115/ SY6502B on it. The oscillator chip in the bottom right is rated at 14.31863 Mhz'; I'm not enough of an Electrical Engineer to be able to tell if it's running at 2Mhz or 1Mhz.
Below the processor are 2 mostly unlabeled ('S 8203 C10793' and 10792) chips that strongly remind me of the MMU and IOU chips on a //e. Note that one pin is pulled out on what I'd expect to be the MMU, the one on the right. Not sure why; it's probably debugging. The ROM sockets next to what I'd expect to be the MMU are empty, then a ROM with a silver sticker and 'KYBD 341 0132 B' written on the socket. Right of the 'KYBD' chip is an open socket, which I'd expect a keyboard decoder chip to fit, since there's a 26 pin connector labeled "keyboard" right above it. Left of that, labeled 'J16', is an 8-point solder pad that might be related to the //e's numeric keypad expansion port.
With 8 RAM chips labeled 'Japan 1G1T HM4864-3' in the bottom right of the motherboard, I'd expect this to be a 64K box. There's also a 'Chargen REV A 1.18.82 (c) Apple' in the bottom left. As mousetext didn't show up until the //c, I wouldn't expect this system to have such; not sure if it's got lowercase capabilities.
Identified as 'Video Conn.', there's a 60-pin slot left of the processor. This is a similar pinout to the //e's AUX slot, but not sure if it's electrically identical. There's only 7 regular A2 slots in back, just like a //e and IIGS.
The power connector looks like it's got solder points for a GS-style 6 pin connector just next to it, but this capability probably was lost for a while in the //e. On the back plane, there's a 9-pin joystick connector, 2 cassette connectors, and a RCA video out. The 16-pin game connector is present on the motherboard, but not in the scan. [There's a white socketed 'NE558N 8128' an inch left of it; no idea why its socket is white.] Also, a set of 4 pins in a row in the back right; those might be for video connectons or something else.
There’a a set of 6 easy solder/cut points in the mid-right; X1 and X5 are connected, the rest are open. After a little more tracing, X6 looks like some kind of shift key mod support. On once side, it heads off to pin 13 of the 16-pin game port (Ann 2), while the other goes to pin 24 (shift) of the keyboard connector. The others are a lot more of a pain to trace down. (At least the board itself is made of the translucent plastic; I can hold it up to a desk light and figure out where the heck everything heads off to The top of X4 and X5 go back to pin 9 of the 74LS02 (OR gates? Been quite some time since I even tried hardware hackery) that’s right of the processor and near the transistor package. X4′s bottom goes to motherboard ground, while X5′s bottom heads off to somewhere under the 74LS154, and then scoots off in another direction I can’t follow. X3 appears to connect off to pin 4 of the game port, pushbutton 2. If it was connected, it’t be driven by the power bus on the top of the motherboard (ground? +5V?). X2 appears to be some sort of alternate power connecting between the top side of the motherboard’s power bus and the bottom. [And also has a thick lead going off to the 'NE558N 8128' in the white socket near the game port]
Less technical comments and blatant guessworkThe obvious comment about this is: This is dated 1981. The //e came out in 1983. What took them so long??? Apple’s longstanding enmity against the Apple II series is probably the reason– they dropped almost all Apple II support when the Apple III was being worked on, and only after they recognized the magnitude of their failure did they come back.
Another comment, thanks to Ian Schmidt, was “6502B? Maybe an Apple /// knockoff?” No real way to tell that without booting it and playing around.
Since this looks simpler than a //e motherboard, what got added to complicate it, and why? Not sure if the ‘Video Conn’ slot has the ability to connect up extra RAM, //e style or ‘Super II’ style. The extra RAM capabilities and double-res are about it for the //e’s additions over the ][+.