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Getting G3 Whisper Perch USB working

Posted by: croissantking on 2023-03-09 13:41:10

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.

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:

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 🙂

Posted by: Phipli on 2023-03-09 14:00:47

Do you want me to send you a couple of ports? I have a box like this if I can find it.

sourcing map PCB USB Female Plug Connector Type-A Short Body Female PBC Mounting Assortment Set, 1 Sets with box (82Pcs): Amazon.co.uk: Electronics & Photo

Free delivery and returns on eligible orders. Buy sourcing map PCB USB Female Plug Connector Type-A Short Body Female PBC Mounting Assortment Set, 1 Sets with box (82Pcs) at Amazon UK.

amzn.eu

Posted by: croissantking on 2023-03-09 14:01:47

Sure!

Posted by: Phipli on 2023-03-09 14:07:49

Or possibly these, price is pretty close to the cost of postage :

USB Type A Connector PCB Vertical GOLD Upright CONEC 33UBAU-04SW11 x 1pc | eBay

Find many great new & used options and get the best deals for USB Type A Connector PCB Vertical GOLD Upright CONEC 33UBAU-04SW11 x 1pc at the best online prices at eBay! Free delivery for many products.

www.ebay.co.uk

Posted by: CC_333 on 2023-03-09 15:10:11

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

Posted by: croissantking on 2023-03-09 15:12:20

You'd only have one port, but you could get one of those period appropriate powered hubs in faux bondi colour 😀

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

Posted by: Phipli on 2023-03-09 15:14:04

something other than a USB card!!

A microscope controller and video capture card?

BTW, does anyone have a lead on a late 90s, early 2000s lab microscope? 😆

Posted by: cheesestraws on 2023-03-09 15:16:26

Good stuff! :-D

Posted by: Phipli on 2023-03-09 15:16:50

You'd only have one port, but you could get one of those period appropriate powered hubs in faux bondi colour 😀

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?

Posted by: croissantking on 2023-03-09 15:19:55

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.

Posted by: Brett B. on 2023-03-09 15:23:38

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.

Posted by: croissantking on 2023-03-09 15:27:41

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!

Posted by: Phipli on 2023-03-09 15:35:03

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.

Posted by: Phipli on 2023-03-09 15:37:13

U1 U2 on the Belkin card is this :

TPS2052 data sheet, product information and support | TI.com

TI’s TPS2052 is a 2-ch, 0.5A loading, 0.9A ILIMIT, 2.7-5.5V, 80mΩ USB power switch, active-high. Find parameters, ordering and quality information

www.ti.com

It protects against shorted USB devices.

Posted by: NJRoadfan on 2023-03-09 15:39:06

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?

Posted by: croissantking on 2023-03-09 15:44:21

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.

Posted by: cheesestraws on 2023-03-09 15:44:35

Edit : or would LP be an inductor pack?

it's marked L, so is it some kind of inductor pack

Wild guess from schematics I've seen elsewhere: EMC protection?

Posted by: Phipli on 2023-03-09 15:51:05

Wild guess from schematics I've seen elsewhere: EMC protection?

Yeah, the filter is transient suppression.

Wouldn't the TPS2052 go at location U20

They didn't necessarily use that same part. Is U20 wired into the port?? Why did they put it over there?

G1 might be a 46MHz clock.

Posted by: Phipli on 2023-03-09 15:52:29

LP1, I don't think it's an IC, the silkscreen doesn't have a notch.

No notch needed if they just cross the package from left to right. It's the same either way up.

Posted by: CC_333 on 2023-03-09 15:55:23

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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