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PPC750GX vs. PPC750GL?

trag

Well-known member
I feel like I've asked this before, but nothing came up in search. Maybe it was lost in the great crash of 2021.

Anyway, anyone know if there are or are not issues in replacing the 750GX with the 750GL? The impression I gather from datasheets is that they're software and pin compatible, but they're also complex, which sometimes leads to unexpected gotchas.
 

LightBulbFun

Well-known member
from what I understand the the 750GL was just a lower power version of the 750GX (and the lower power version of the 750FX was similarly called the 750FL) they are fully interchangeable and identical otherwise, they are the same hardware just binned for different applications :)

(I have seen 1Ghz PowerLogix 750GX CPU ZIF cards with 800Mhz 750GL's for example)

I actually have a few of both CPUs in the collection that I bought a few years back, I really need to unearth them and see whats what because I want to send a couple to @max1zzz if he still has some 750FX based iBooks on the operating table, im really curious to see if a 750GX/GL can be swapped in (since the 750FX/750GX are pin compatible) although the BootROM of the iBook might need patching first (but thats not hard to do if it is needed)

another thing that would be cool would be if it would be possible to remake the PowerLogix 1Ghz G3 upgrades, they look deceptively simple

I had one for a short period of time that I was drop shipping for a fellow collector who very kindly let me play with it for a bit, and as far as I can tell they contain no active logic, its just ZIF PCB!

which I find really curious because they work in a PowerMac G3 BW without any Firmware patching and report back as a regular 750 to most software, so im really curious as to how PowerLogix did that with no special logic on their CPU card etc!

I also wanted to figure out what resistors set the PLL speed on those ZIFs since somewhat annoyingly PowerLogix had them set to 500Mhz in hardware which you then would raise to 1Ghz with their software (the 750FX/750GX having software controllable multipliers) but said software got broken by OS X 10.4.9 or there abouts, I personally dont really care about a low speed/power mode so it would be cool to have on that ran at full speed regardless of what inappropriate OS I am running on the machine its installed in :)

theres actually a whole bunch of 750GL's on ebay right now if anyone wants some to experiment with :) https://www.ebay.com/itm/124258517963
 

max1zzz

Well-known member
I really need to unearth them and see whats what because I want to send a couple to @max1zzz if he still has some 750FX based iBooks on the operating table
Indeed I do! The 14" 800Mhz that was the last iBook I was working on in my (Now lost) thread on reworking iBook G3 GPU's has still not been reassembled as I still need to swap the RAM out on it, I would be happy to plop a 750GL on it and see what happens :)
 

trag

Well-known member
theres actually a whole bunch of 750GL's on ebay right now if anyone wants some to experiment with :) https://www.ebay.com/itm/124258517963

Yes, that's what got me wondering again. Thank you for your detailed reply, BTW. That the 750GL has been observed on the PowerLogix cards pretty well nails the compatibility. That's excellent.

Pins for setting the default clock multiplier should be described in the datasheet, but figuring out which resistor they connect to on the ZIF card could be tricking.

The difficulty in replicating the PowerLogix 750GX ZIF is that darned PGA header on the bottom of the card. I have not been able to source such a thing anywhere. Molex could probably do a custom run but how many thousands would be the minimum?

@max1zzz The link @LightBulbFun provided has 10 750GLs for $30 + shipping. I'm not sure about shipping to the UK, though.
 

max1zzz

Well-known member
Shipping to the UK is $60 which tbh isn't too bad (bearing in mind UTsource are selling them for £23 each!) but my project budget is seriously depleted this month after buying all the bits for the LC III replica..... Maybe next month :)
 

trag

Well-known member
Well, they still have more than 250 lots, so with luck, you'll refresh your budget before they run out...

Although, since I bought what I felt I could afford, they've already sold another ten lots in just the past day.
 

LightBulbFun

Well-known member
here we go I managed finally unearth my 750GX/GL's! I thought I had 3 of each but sadly not

however @max1zzz if your still interest in a 750GX or GL ill happily send you one next time someone in this household is going past the post office! (is your address the same as it was from the G4 iMac G3 adventures? :) )
1632494263066.png
I do have a feeling the 750GX might be used pulls sadly, but I THINK the 750GL's are NOS (both where sold to me as NOS but clearly the 750GX's have residue marks and I think I can see little bits of thermal goop on the side of the dies even)

let me know which you prefer and ill hopefully send it off in the not to distant future! :)

BTW here is the PowerLogix ZIF I had my hands on for a short while, I never verified it, but I strongly suspect R10-R13 are the PLL resistors and also of note how the PCB says 750FX on it, clearly the same board or similar to what they used for their 750FX upgrades (which makes sense as the GX is supposed to be pin compatible)
1632494869777.jpeg

and here is one showing a 750GL

1632495454968.png

@trag with regards to the pin header, I wonder if you could make your own? its just a whole bunch of surface mount Pins, perhaps you could get some suitable wires or pins, cut them to length then put them in a 300 pin Jig of sorts, put the PCB on top and reflow all into place, just like BGA soldering really :)
 
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trag

Well-known member
@trag with regards to the pin header, I wonder if you could make your own? its just a whole bunch of surface mount Pins, perhaps you could get some suitable wires or pins, cut them to length then put them in a 300 pin Jig of sorts, put the PCB on top and reflow all into place, just like BGA soldering really

If I ever get there, I might try that.

There was a lot of hundreds of G3/233 (maybe some 266) ZIF cards sold for scrap a few years ago. I with I had picked that up. I could salvage the pin headers off of all those old ZIFs that no one is ever going to downgrade to.

BTW, nice photos. Thank you. Do you have an image of the back of the ZIF?
 

LightBulbFun

Well-known member
Yeah :) BTW for what its worth while most ZIF's I have seen use the same pin-header with a black plastic interposer, I have noticed sonnet ZIF's used something else with a white/translucent interposer, perhaps something to look into incase it tells you where to find em or how to go about making your own :)

(I need to see if I can unearth my 500Mhz Sonnet G4 ZIF I seem to recall there was actually a slight gap between the PCB and interposer so you could see the solder joints of each pin)

Thanks :), however that photo of the ZIF with the 750GL is from the CPUShack :) https://www.cpushack.com/CPU_Photos2/ibm/

who do also have this picture of the back :) as a side note I wonder who "962, Inc" are/were, were they just the company that made the bare PCB or where they more involved?

1632531521000.png
 

trag

Well-known member
I have noticed sonnet ZIF's used something else with a white/translucent interposer, perhaps something to look into incase it tells you where to find em or how to go about making your own

That could be a useful lead. Does anyone here have a contact at Sonnet that might provide information?

I can/will try contacting them myself, but I have not had great luck in the past, so if someone already has a contact that would be better.
 

trag

Well-known member
I received the 750GLs I ordered from Zombie Parts on Ebay. I was a little worried at first, because they lack an IBM logo before the "PPC750...." part number. There's a sort of hollow square there, where, at first, I thought "IBM" might have been somehow gouged/lasered out.

Then I had a memory ping. DId a little digging, and the squiggels in that little square are the emblem for Rochester Electronics, who took over support from IBM.

rochester.png
 

max1zzz

Well-known member
Well, they still have more than 250 lots, so with luck, you'll refresh your budget before they run out...
They still have 365 lots, hopefuly they still have some left in a couple of weeks when the project budget has been replenished :)
however @max1zzz if your still interest in a 750GX or GL ill happily send you one
Thanks for the offer, But since I'm going to buy some soon (and since you only have a few) i'll hold off for now :)
 

LightBulbFun

Well-known member
I received the 750GLs I ordered from Zombie Parts on Ebay. I was a little worried at first, because they lack an IBM logo before the "PPC750...." part number. There's a sort of hollow square there, where, at first, I thought "IBM" might have been somehow gouged/lasered out.

Then I had a memory ping. DId a little digging, and the squiggels in that little square are the emblem for Rochester Electronics, who took over support from IBM.

View attachment 34456
interesting! it reminds me of the e2v 7410's etc :) https://www.cpushack.com/2015/04/09/the-e2v-powerpc-and-hitce-packages/

do you have any pics of the CPUs? do they look like new CPUs or used/reballed pulls?

They still have 365 lots, hopefuly they still have some left in a couple of weeks when the project budget has been replenished :)

Thanks for the offer, But since I'm going to buy some soon (and since you only have a few) i'll hold off for now :)
No problem! saves me having worry about getting to the post office! but if you do end up needing one from me or something the offer still stands! :)
 

trag

Well-known member
do you have any pics of the CPUs? do they look like new CPUs or used/reballed pulls?

I can't tell. I'll leave it to the audience to decide...

IMG_1496[1].JPG

IMG_1497[1].JPG


IMG_1498[1].JPG


IMG_1499[1].JPG


IMG_1500[1].JPG

BTW, they weren't shipping in trays. They took a sheet of cardboard and covered it in an anti-static bag. Then they set the chips, balls down on the surface of the bag. Then they taped the chips in place on the bag. It's probably effective, but it was certainly unconventional.

Anything that looks like adhesive residue on teh tops of the chips is probably from the packing/shipping method.
 
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