How to identify G4 CPUs?

[bakkus]

Since I don't know all that much about PPC past 601 a question popped up while rummaging through parts bins:
What's the best way to identify what "generation" G4 CPU daughtercard one has?

Hopefully this thread can be turned into a valuable resource for anyone with the same question.

And what are those generations?

• The G4 "AGP", G4 "Gigabit Ethernet" and the G4 "Digital Audio" share the same looking cards.
  Be aware that the AGP has a 100MHz system bus, and the GE, and DA run at 133MHz. This means that since CPU frequency is calculated by "system bus times fixed multiplier", the same CPU cards will be clocked differently: 100MHz * 4.5 = 450MHz G4 in an AGP. The same CPU card in a DA will run faster, since 133*4.5 = "600MHz". This is a quite substantial overclocking, so be careful.
  They usually look very much like this:
  
  
  
  Note the THREE (3) mounting holes.
  
  
• Then there are QS (QuickSilver) cards? How to identify them?
  
  
• Lastly there's the Mirror Door Drive, or MDD generation. What sets these CPU boards apart from the QS ones?

And going deeper into tinkering territory: Which ones can be made interoperable?
I'm aware there's some trick getting newer cards working on older machines. But exactly how? Without scrolling through 148 pages of bitrotted forum posts?

 

[Volvo242GT]

@herd over at the other forum has a lot of information about the various G4 cards, as well as ones he's offering up as upgrades for those of us who want something faster.

 

[Certificate of Excellence]

I have a few loose daughter cards for QS & MDD. First off the QS is green

and they debuted in 2001, so likely the daughter card will be dated as such (All of mine are). QS discontinued 2002 at the August introduction of MDD so while I havent run into a 2002 dated card myself, I have seen some photos of a few 2002 dated QS daughter cards on the interwebs.

and MDDs are blue. Below are a couple 1.25ghz MDD daughter cards. You can see the variation in color and some different components were used despite being the same card. MDDs debuted in 2002 thus the daughter cards will reflect that date (at least I have not run into anything later). MDDs discontinued January 2003 but was brought back July that year as a OS9 compatible machine out through 2004.

 

[Certificate of Excellence]

I havent done the mod myself but it is my understanding that a QS daughter card can be used in GE & DA. A 12v rail from the PSU needs to be soldered to the unused upper left corner mounting hole and the QS daughter card - the way it connects forces it to protrude out further (towards the left side of the case door), requiring the PATA port to be removed in order for the daughter card to sit correctly. Below is a photo of how a QS D card would sit in a DA. You can see how it would stick out beyond the pata port which would push up on the card.

Below is the unused mounting screw hole where the 12v rail needs to be connected.

Again I’ve not done it myself but have researched it while waiting to run into cheap GE or DA lobo bits to butcher. Another difference is the cpu itself, the QS is a 7450 and the MDD is a 7455 cpu so if you look closely, they both state that on the die itself. The 733mhz QS pic shows this pretty clearly.

 

[Certificate of Excellence]

@herd over at the other forum has a lot of information about the various G4 cards, as well as ones he's offering up as upgrades for those of us who want something faster.

There is alot of helpful experience/knowledge about G4 era Powermacs over on macrumors as well (which is where I did alot of my research on D card compatibility). Quite a few folks over there still daily-ing or close to that their PowerPC Powermacs. Coincidentally, I was doing some maintenance this week on my dual 1ghz Quicksilver (been a 3 or 4 years & needs to be cleaned). Anyways, here is a photo of that daughter card vs the single cpu 733mhz above for comparison.

The date is a little harder to find on these - upper right hand quarter on the backside of the daughter card. A related point to be aware of are the QS heatsinks are different for the single and dual cpu models. The dual CPU heatsink is bigger. Below are some pics of their difference in design - the dual cpu in the pic has the red decal. It can be difficult to spot the differences in online auctions leading to buying/trading for the wrong unit.

The part numebrs on the bottom are convenient ways to differentiate them as well vs just visually which is suprisingly easy to mess up.