What Am I?

[AichEss]

This board came to me in a box of Apple II stuff and it obviously isn't Apple II.

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Google tells me that MacSnap is gear for early Classic Macs - 128s, 512s and the like - but I do not find anything specific about an "Aux. ROM Board".

Surely the answer is here.

Thanks,

Aich Ess

 

[markyb86]

I'm 90% on this, but I think that is a 3rd party ROM upgrade to use a larger capacity floppy drive?

 

[AichEss]

Like to go from 400 kb drives to the 800 kb units?

 

[markyb86]

Yeah, that's what I am thinking. The only other thing I can find was to give the 128/512k SCSI. But those boards are much larger.

 

[Gorgonops]

That is actually an incredibly intriguing doodad. I would love to know what the contents of that EPROM are, but... if I had to take a wild guess I think what this thing might be for is to dynamically apply a few single-byte patches to the Mac ROM. (If you really feel like a project you could examine the traces and reconstruct the schematic so we could figure out under what circumstances the EPROM is enabled.) Since the Mac uses a 16 bit data path to ROM I think it's pretty unlikely that that there is a complete driver/extension in it.

If I had to hazard a guess, my gut feeling is this device implements a few hacks (which literally might just be changing a few one byte constants) to the hardware initialization routines in order to enable a really old Mac (perhaps only Macs with the original 64k ROMs, which would mesh with the 32k size of the EPROM) to recognize more than 512k or RAM, and thus work with one of their "MacSnap" one or two MB clip-on memory boards. It appears that when said board was sold with a SCSI expansion (with resided in *both* ROM sockets and required 128k ROMs) the complete package was called the "MacSnap 524S". This just says "524", so if the "S" means SCSI...

 

[TheMacGuy]

After a quick Google search, it looks like the company's name is Dove, and MacSnap being a brand. From this company I'm only finding SCSI mods and RAM upgrades for the early compacts, but no ROM upgrades. They apparently were focused on making the 128k and 512k models into Mac Pluses, so it makes me wondering if this board was part of a floppy drive upgrade sold by the company.

If I had to hazard a guess, my gut feeling is this device implements a few hacks (which literally might just be changing a few one byte constants) to the hardware initialization routines in order to enable a really old Mac (perhaps only Macs with the original 64k ROMs, which would mesh with the 32k size of the EPROM) to recognize more than 512k or RAM, and thus work with one of their "MacSnap" one or two MB clip-on memory boards. It appears that when said board was sold with a SCSI expansion (with resided in *both* ROM sockets and required 128k ROMs) the complete package was called the "MacSnap 524S". This just says "524", so if the "S" means SCSI...

This is highly likely. Maybe they sold more then 1 kit.

Here is some more info from VintageMacWorld I found from a Google search:

http://www.vintagemacworld.com/macsnap.html

 

[AichEss]

OK.

I went through the Google search again and, like TheMac Guy, found the best picture of a MacSnap installation to be in the linked he referenced. I gather that the pic of the logic board shows both the SCSI (524S) and RAM (?) expansion boards in place.

I don't know where the ROM chip is located on a 512k logic board but it sho nuf needs be under one of the expansion boards, most likely the SCSI board.

This close-up shows how snuggly the MacSnap expansions fit on the 512K board. In the centre the MacSnap SCSI card can be seen clearly. This card plugs into the

ROM sockets and Mac Plus ROMs are installed to provide support for SCSI and the

internal 800KB floppy drive (a standard early series 800KB drive is fitted).

Based on this quote, maybe Gorgonops and markyb86 each have a part of it - my little board is just a mounting adapter for the SCSI board or to install the RAM expansion & 800k drive capability without the SCSI board?

Does anyone have a use for it?