Mystery expansion in a Classic

[tecneeq]

So, i was just looking into that old and beaten Classic i had in a box for what seems like years. Caps are leaked, green muck on the traces, it still starts, but without sound. The hardware is pretty much the usual, memory expansion to 4 MB and a hard disk.

And i found this:



The daughterboard is connected with that white thing at the top. Which looks like that from the side, only three traced connections really:



This is the top view, sorry for the bad picture:



The chip has nothing on it, except this sticker:



The bottom view has an empty socket. I would say that a FPU could fit:



It says:

MODAM MAC CLASSIC ADAPTOR

© 1990 MEMORY PLUS

and:

PH X1B-S03

The white connector board is, at least i believe it is, just a power connection, not a data connection. This should be the data connection, 8 pins, but nothing was connected:

 

[tecneeq]

There it is:



Any ideas what this part does?

 

[tecneeq]

And another view:

 

[mcdermd]

All I've found is that IPT is probably "Information Presentation Technology". Their primary product was "uShare" which was a file sharing app to network Macs with Sun, NeXT, DOS and Apollo (and others?) . Although known primarily for the software, it looks like they may have also produced hardware to enable networking. It could be that this board is such a network interface. Any FCC IDs?

 

[mcdermd]

Strike all that - I see the marking of "MODAM" "MEMORY PLUS". That's a video card. You're missing the daughter card, though.

 

[tecneeq]

I swear to you, i tried this query with google yesterday:

"MODAM" "Memory Plus"

It always resulted in modem stuff. But today it results in real results that are relevant to MODAM, 68kmla is the first result. Strange. :O

Anyways, In the box was a cable with what looks like a VGA or Serial port on one end and the 8 pin connector on the other end. I didn't think anything of it, because it was in a ball of other cables, but it fits!

So here is my theory, it's not a card for graphics, because there are only three traces that connect the board to the motherboard. The other graphics cards had a PDS connector. I only have 3 pins on the one side and 8 on the other. However, three is enough for power and a serial connection, right? Could it be another serial port?

The oscillator on the board has two pins and is 14.3182mhz, if that is saying anything.

Is there any software that i can run that would identify the board somehow?

 

[tecneeq]

I found this old listing on Ebay, it appears to have similar parts, except that i have 5 instead of 9 chips (but i only have one output connector) and i don't have a ROM chip (but no Nubus either, so that might explain that):

http://www.ebay.com/itm/Apple-Mac-II-Video-Card-NuBus-Extremely-Rare-Gray-Scale-Card-Tested-Working-/390571588407?nma=true&si=inQysCrgVRoVQf1%252FBzvJk6eEFr4%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

So yes, it's probably a video card. But i doubt a daughter card is needed. I may be needing a portrait display .

And it still bugs me that the only connection to the motherboard are three traces of which at least one is ground and the other is power. Is that even possible?

 

[Trash80toHP_Mini]

The SIP VRAM is a dead giveaway that it's a VidCard . . . what data is printed on the SIPs . . .

. . . paucity of MoBo connections makes me think might be getting its power a/o ground from another source . . .

. . . trace the connections on the MoBo . . .

. . . I'm guessing that you've got a 5V connection and two signal lines . . .

Does the Classic have a dedicated Video Controller or is it all a function of the 68000?

< WAG >

I'm thinking internal grayscale and all you're missing is a custom Y-cable placing that card in between A/B output and the CRT input.

I'm also guessing that 5V is the only thing missing on the original cable.

Could be 4 or 8 level grayscale given those two(?) signal lines, depending upon what's available on the CRT connection cable.

Anybody got the SE/30 schematic handy? :?:

< /WAG >

 

[MinerAl]

if it's one-bit video you'd only need one lead, right? So power, data, and ground would be your three leads.

Is there a diagram of what the Classic's edge connector positions are/do?

 

[Trash80toHP_Mini]

Ground and the first bit (B&W) would be on the A/B<->CRT Cable, but probably not 5V . . .

. . . leaving the possibility of one or two bits of addressing(?) from the 68000 bus on the interface . . .

. . . that'd mean at least two bits/four level gray . . .

. . . maybe four bits//eight level gray :?:

Dunno, it's a WAG-n-a-shot in the dark. :-/

 

[tecneeq]

The board is connected to J10, pad 15 (leads to R94 and R95, which i then lost under the sound chip), 13 (leads to C55), and 11/10 (which i believe is ground).

Yes, it's a video card, the 4 VRAMs are HM53461ZP-10 with 24 pins. Each has 64k words, each word is 4 bit. So i have 256k 4bit words or 128kByte for all four VRAMs.

Asuming portrait display resolution (640x870), i have 556800 pixels. Then it's not enough space for greyscales in the VRAM, so each pixel is either on or off.

 

[tecneeq]

Ok, i just took another look. The space where i though a FPU might fit? Fits exactly on the 68000 of the classic. At first i thought nothing of it, but it might be that the pins of the empty connector make contact with the pins of the 68000. However, it doesn't look very exact, i would at least have expected some screws or so, so that the card always has good contact.

Do you think the empty slot seen in picture 5 of the first post could make reliable contact with the 68000 pins? Would that even make sense? Or is it just so that the card is in the right position for the small power connector board?

 

[James1095]

14.3182 MHz is exactly 4x the NTSC colorburst frequency, and is commonly used in devices that generate NTSC video. That does tend to suggest that this is a video card of some sort, although it's also possible that like the 3.57MHz colorburst crystals, it was a mass produced part, making it cheaper and thus occasionally used in applications that had nothing to do with video.

 

[tecneeq]

No doubt, it's video.

But nothing happens at the output. I guess i have the wrong display (1280x1024 HP TFT from about 2004).