Studying the Beige G3's Modem slot

[croissantking]

I've been examining the Beige's Modem slot as I'm designing a peripheral for it.

I put this image together which shows exactly which lines have been removed as compared to a standard Comm Slot II. It really does just have the bare minimum of signal lines required for a modem, but usefully all the power lines are there.

You could in theory bodge the 50 or so PCI signal lines from the Perch edge connector – or indeed the USB chip footprint – to the corresponding pins on the modem slot and get a fully functional CSII slot.

 

[croissantking]

Correction to the G3 Modem slot - missed these out.

 

[Durosity]

Do we know why they decided to leave all these lines out?

 

[croissantking]

Do we know why they decided to leave all these lines out?

At least on Version 2 of the Personality card, those lines are used by the USB chip. I suppose on Version 1 those lines are unused – were they keeping them in reserve for a future USB chip (or another I/O peripheral)?

 

[croissantking]

Also maybe cost saving – and considered unnecessary with the Beige's built-in Ethernet.

 

[adespoton]

I'd guess you're probably right with the USB route -- they were probably mid-way through implementing USB when V1 was released, and had been able to free up lines for it without impacting modem functionality, but hadn't actually integrated USB yet. Logic there would be: they could release V1 in its stripped down but known-functional form, and then have flexibility in adding future features.
So not just component and assembly cost savings, but also cost savings in future design upgrades and testing.

 

[Durosity]

That does make sense! I’d really love to be able to get a v2 AV personality card for my AIO one day.. particularly if it has the DVD decoders chip on it (did that exist?) and add the USB chip to it!

 

[croissantking]

That does make sense! I’d really love to be able to get a v2 AV personality card for my AIO one day.. particularly if it has the DVD decoders chip on it (did that exist?) and add the USB chip to it!

The DVD decoder card (Bordeaux) doesn’t have an AIO video header, unfortunately, so you’ll have to settle for a Wings A/V.

 

[Durosity]

Darn! I was hoping for a fully loaded unit!

 

[croissantking]

Bordeaux are unobtainium anyway.