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Getting G3 Whisper Perch USB working

croissantking

Well-known member
Right, following on from the discussion in the PowerMac forum, this project deserves its own thread.

Later revisions of the Personality card (Whisper, Wings and Bordeaux) that comes with every Beige G3 have footprints for a single USB 1.1 socket and supporting circuitry, similar to that found on early USB PCI cards.

Prototype machines have been seen with this USB socket, but no production machines ever had it installed. We don't know if it was at one point planned for the beige to have built-in USB, or if the footprint was meant solely for developement.

I have a soft spot for the Beige and was thrilled to find it has this 'secret', hidden feature and given nobody else has tried to get it working (afaik) I'm jumping in.

Over the past few days I've been attempting to understand the footprint better and thinking about how to populate it correctly as we don't have any kind of reference.

I have selected a Belkin PCI card that I got for £2 off eBay as a parts donor, since its CMD 0670 chip is pin compatible with the Opti Firelink that's used in the early iMacs and B/W G3s. I have also seen this 0670 chip in a prototype iMac that was featured on Krazy Ken's Tech Talk on Youtube. I felt it was safe to assume that the Personality card's footprint would be designed around one of these chips.

This evening I decided to desolder the 0670 and fit it to the Whisper card with a few supporting filter capacitors.

IMG_9754.JPG

First boot attempt was a no-go, got a chime but then no picture and no boot. Examined the chip and noticed a solder bridge between an address line AD24 and an adjacent VSS (hope this didn't damage anything). I cleaned this up and then the Mac booted just fine. This is what ASP shows:

Screenshot 2023-03-09 at 21.17.24.png

It's detected, and shows the same info that it did when it was on the original PCI card. So this is a big success. It's interesting to see 'Slot PERCH' in the list of PCI devices, I don't think that's ever generally been seen before. There is no USB bus shown at the top of the window, but maybe I'd have to populate more of the supporting circuitry to get that to show?

I am going to continue working on this and posting further updates. I hope there's some interest from the rest of the community - but if not I will do it for my own pleasure anyway :)
 
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CC_333

Well-known member
This is neat!

If successful, this would basically eliminate the need for a USB card, thereby opening up an extra PCI slot for... something other than a USB card!!

c
 

croissantking

Well-known member
You'd only have one port, but you could get one of those period appropriate powered hubs in faux bondi colour :D

One could also presumably hack in a second port (and even have it front mounted), because the chipset supports two.
 

Phipli

Well-known member
You'd only have one port, but you could get one of those period appropriate powered hubs in faux bondi colour :D

One could also presumably hack in a second port (and even have it front mounted), because the chipset supports two.
Looks like you might have something to add in these locations as the traces go to and through them. Some just caps, but that chip is probably a protection circuit.

Edit : or would LP be an inductor pack?

Screenshot_20230309_231538_Firefox.jpg
 

croissantking

Well-known member
Looks like you might have something to add in these locations as the traces go to and through them. Some just caps, but that chip is probably a protection circuit.
View attachment 53412
Yes, I mapped this part out on my schematic. L22 and L24 are inductors and have to do with hot plug protection.

I am not sure what goes at location LP1. It looks like a resistor pack, except it's marked L, so is it some kind of inductor pack? The lower four pads are not connected to anything.
 

Brett B.

Well-known member
Really cool, I am surprised nobody has figured this out already.

Lack of onboard USB has always been a frustration, if you wanted better video, 10/100 Ethernet and faster SCSI you had to give up USB... or keep USB and give up 10/100 ethernet... or a SATA card and give up something else. Always give and take!! Wish the G3s had four PCI slots.
 

croissantking

Well-known member
Really cool, I am surprised nobody has figured this out already.
I agree, there are some incredibly talented people here (just look at what's been done with the SE/30) who could solve this one with their eyes closed and their hands tied behind their backs!
 

Phipli

Well-known member
L22 and L24 are inductors and have to do with hot plug protection.
You can just borrow these straight from the belkin card (L1 and L2, or L3 and L4 - they even provided spares ;) ). Might be worth looking up what U1 is on their card too as it might give clues about LP1.

Just past LP1, the bunch C109, 110, R61, R5, looks like a filter.
 

NJRoadfan

Well-known member
The fact that it just "worked" on the PCI bus is pretty amazing. The datasheet should hopefully have a sample implementation for the chip. Passives on USB cards are going to be for hot plug protection, namely fuses. I wouldn't be surprised if one of them tells the chip that you only have one port vs. two. Is the USB Card extension installed?
 

croissantking

Well-known member
You can just borrow these straight from the belkin card (L1 and L2, or L3 and L4 - they even provided spares ;) ). Might be worth looking up what U1 is on their card too as it might give clues about LP1.

Just past LP1, the bunch C109, 110, R61, R5, looks like a filter.
They are a bit too large on their card, so will have to order smaller ones.

Wouldn't the TPS2052 go at location U20 on the Apple card? LP1, I don't think it's an IC, the silkscreen doesn't have a notch.

All of the empty stuff to the left of the main 0670 chip relates to USB, as well.
 

CC_333

Well-known member
Wish the G3s had four PCI slots.
Well, if you count the PERCH slot (which, if I'm not mistaken, is a superset of PCI), then technically, they do have four slots, it's just that that fourth slot is always occupied by the personality card.

c
 
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