assembled one themselves using mostly parts which had been deemed too > I was thinking something like that, or it was repaired at one point and this particular board was on hand to use as a replacement. The key would be figuring out what the apparent serial number '1-00494' means.

On 12/29/18 6:59 PM, Brad H via cctalk wrote: For what it's worth, looking at a photo, my[1] machine's board looks more like "3P10083 REV A" down by the front edge of the board, unless there's some dirt or other debris making it look like a 'P' rather than an 'A'. Unfortunately I don't have a photo of the entire board, so I'm not sure what the serial number top-left is (and if the data there typically differs 1982, and the case is one of the more rugged 1a ones. [1] At least I think it's mine :-) I picked up two machines from another collector a few years ago, and one of them went off to another list member, so it's possible that the photo I've got is of that one. Interestingly the main Wikipedia article for OCC says that the first machines went out in July and they sold 11,000 in the eight months after that - but the article specifically for the Osborne 1 seems to suggest that systems went out in April (but again with 11,000 sold in the eight months after). The main article mentions a 10-15% failure rate, which seems incredibly high - presumably pressure to meet demand and repair faulty systems was enormous, which could explain how a prototype / early board found its way out into the wild. Jules

There are definitely some differences. For example, the ROM BIOS on mine is contained on two 2716s instead of a single 2732 as in the later boards. There's a few jumper wires on the board too. I imagine it's largely the same, although if it were completely I'm not sure why they'd do a full redesign and not, like you said, use some of that extra space for more RAM or something. Lee himself didn't really know.. all he said was that that space, in the prototypes, was occupied by linear voltage regulators that were changed/designed out after. Maybe what I'll do is make a complete list of the ICs and see how it lines up with a later production board. And then compare other components. -----Original Message----- From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Jules Richardson via cctalk Sent: Saturday, December 29, 2018 4:21 PM To: cctalk at classiccmp.org Subject: Re: Osborne-1 with prototype-based motherboard On 12/29/18 2:53 PM, Brad H via cctalk wrote: Is it just the board layout that's different, or does it appear to be a completely different animal, schematic-wise? (I mean, is there a possibility that the common schematics could still be used for fault diagnosis, despite the different chip locations) I wonder why the board layout changed? I mean sure there was a lot of unused space in yours, but it's not like the production boards were physically smaller. I'm surprised that additional space couldn't have been used for some other potential future purpose - RAM expansion or whatever. cheers Jules