Bussing around with a G3 Beige XPC106 Memory controller upgrade

LightBulbFun

macrumors 68020
Original poster
Nov 17, 2013
2,298
2,233
London UK
so I have a G3 beige mini-tower in pretty nice shape its a Rev B unit

now as many people know I love to tinker with my Computers and I knew that you could in theory overclock the bus on a G3 beige from 66.8Mhz to 83.3Mhz, so I gave this ago on my G3 beige a while ago :)

sadly it was not stable at all and would barely POST, Game over, back to the stock 66.8Mhz right?

Nope, Just replace the Main "North bridge" for a faster one, simples :D

heres what I did to get my 83.3Mhz bus speed G3 beige:

I took a spare Rev A G3 BW board removed and reballed the 100Mhz XPC106 off of it

then I took the G3 beige board, removed the 66Mhz rated XPC106, cleaned up the pads on the Logicboard and soldered on the "new" 100Mhz rated XPC106 :)

and it worked! the G3 beige booted right up and I was able to set the bus speed to 83.3Mhz without any stability issues (of course im using PC100/133 DIMMs) (I ran a few GeekBench loops and over 120 passes in Gauge Pros memory tester without issue)

I do wonder if theres a Jumper config that would let me set the bus speed to 100Mhz, a 100Mhz bus speed G3 beige would be pretty epic.

the XPC/MPC106 also known as Grackle, is the Memory/PCI/Bus controller/"North Bridge" in: G3 beiges, G3 BWs, G4 Yikes!s, WS/PDQs, Lombards and tray loading iMac G3s. in theory the same swap I did here could be done to any of those machines alloying them to run a 83.3Mhz bus nice and stable

of course I have some pictures :) but "sadly" with my new equipment, the BGA soldering was going so well i forgot to stop and take some pictures during the swap... :oops: so no bare pads shot im afraid. (I got a T8280 Hot plate which combined with the TS100 soldering iron makes BGA soldering such big boards much easier )

upload_2018-5-20_21-53-3.png


upload_2018-5-20_21-55-4.png


and finally the money shot of the 100Mhz rated "North bridge" Grackle chip on the G3 beige logic-board :) where it says ARX100, it says ARX66 and ARX83 on 66/83Mhz rated parts, incase your wondering how to tell the speed of your XPC106 chip :) the chip I fitted/pictured was made 4th week 1999

upload_2018-5-20_21-57-8.png
 
Last edited:

weckart

macrumors 603
Nov 7, 2004
5,032
2,320
Was the flakiness of the B/W G3 A rev down to the controller or the firmware? Just wondering if you've swapped stabilty for performance.
 
  • Like
Reactions: LightBulbFun

LightBulbFun

macrumors 68020
Original poster
Nov 17, 2013
2,298
2,233
London UK
Was the flakiness of the B/W G3 A rev down to the controller or the firmware? Just wondering if you've swapped stabilty for performance.
Good Question. :)

I was thinking about this while contemplating the swap. I think the flakiness of the Rev A G3 BW was down to its overall Logic-board design and possibly firmware, rather then 1 specific problem component. im pretty sure the Rev B BW and the Yikes! use the exact same Grackle chip but ill have to verify this (all 3 of my G3 BWs are Rev A units sadly) its also worth noting that currently im running the Grackle chip at 83Mhz rather then at the 100Mhz its rated for, so if it was on edge at 100Mhz it should be nice and comfy at 83Mhz (indeed it does run noticeably cooler then it did in the BW G3)

and so far the G3 beige has been nice and stable, in-fact I just finished using the G3 beige, to image 7.5.3 to my Macintosh SEs 40MB SCSI HDD :) (as my Macintosh SE is not a FDHD one and does not have any FDHD components/upgrades)

upload_2018-5-21_13-28-12.png


bonus shot of a 40MB SCSI Drive in Leopard :D

upload_2018-5-21_13-33-30.png
 
  • Like
Reactions: AphoticD

weckart

macrumors 603
Nov 7, 2004
5,032
2,320
SSW 7.5.3 on an SE with 2.5MB RAM is just cruel. :(

You can just about run Finder and not much else. I use Zip and Jaz drives to get stuff on and off and those can also be used to run the SE on. Those 800Kb drives are a pain in the backside and it's getting hard to find 720Kb floppies cheaply to use on them.
 

DearthnVader

macrumors 65816
Dec 17, 2015
1,150
5,737
Red Springs, NC
Great work, sound like it's time to clock chip too.

I forget the rating of the fixed frequency oscillator that sets the timebase on the Old World G3's, but you maybe able to push it to 100mhz by swapping it out.

However, it depends on what other than the bus frequency and memory frequency are relying on that oscillator, as things like built-in sound, ethernet, and video may not work very well if they are synced with it.

Normally the PCI bus has it's own oscillator, but it's been a long time since I had a Beige G3.
 

LightBulbFun

macrumors 68020
Original poster
Nov 17, 2013
2,298
2,233
London UK
SSW 7.5.3 on an SE with 2.5MB RAM is just cruel. :(

You can just about run Finder and not much else. I use Zip and Jaz drives to get stuff on and off and those can also be used to run the SE on. Those 800Kb drives are a pain in the backside and it's getting hard to find 720Kb floppies cheaply to use on them.
Hey I was able to open Mac Draw II :) (but not claris works) however indeed 7.5.3 is quite sluggish on the ol 8Mhz 68000 CPU :D I will be getting 4MB of RAM for the SE at some point soonish hopefully, and get it online :) sadly this is my only 68K and I dont own any other SCSI gear. id like to get an external SCSI HDD at some point... luckily I have a bunch (like 30+) of TDK 1.44MB floppy disks that will happily format to 800K and seem to be holding their data at 800K. so I can at least get some stuff on and off the machine via the sneaker-net.

Great work, sound like it's time to clock chip too.

I forget the rating of the fixed frequency oscillator that sets the timebase on the Old World G3's, but you maybe able to push it to 100mhz by swapping it out.

However, it depends on what other than the bus frequency and memory frequency are relying on that oscillator, as things like built-in sound, ethernet, and video may not work very well if they are synced with it.

Normally the PCI bus has it's own oscillator, but it's been a long time since I had a Beige G3.

I dont plan to try and overclock this machine by changing any of the crystals, as you say, it will mess with the timing/speed of Everything and lead to no end of issues.

on the PCI thing, I know on the G3 beige the PCI Bus is tied somewhat to the main bus speed (for example 66.6Mhz and 83.3Mhz Bus speeds the PCI bus runs at 33.3Mhz but at 70Mhz the PCI bus runs at 35Mhz and at 75Mhz it runs at 30Mhz)
 
  • Like
Reactions: AphoticD

LightBulbFun

macrumors 68020
Original poster
Nov 17, 2013
2,298
2,233
London UK
I have been doing a bit more sleuthing trying to figure out how to clock the G3 beige up to 100Mhz when I came across this:

https://www.nxp.com/products/no-lon...-evaluation-system-discontinued:YELLOWKNIFEX4 a Motorola development board/system called YellowKnife

its a very weird and interesting board, its of an ATX form factor with a fairly typical PC IO layout but is PowerPC based and has a MacOS ToolBoxRomImage and apparently is compatible with Mac OS? (they mention the TBXI is 4MB so im pretty sure it has OpenFirmware too)

spec wise its quite similar to the G3 beige (with some hints of G3 BW) and uses the same CPU Socket, although it uses an 11 pin jumper block like a G3 BW for settings rather then the 9 pin jumper block used in the G3 beige so its going to take extra sleuthing to figure out how to get the G3 beige up to 100Mhz bus

I have also been looking all over for information on the socket used in the G3 beige through to Yikes! systems, so im also glad to of finally found information on the socket including a detailed pinout :) (its actually 288 pins not 300 as commonly reported. its PC equivalent is Socket 3)

it would be interesting to hear if anyone else has see/come across the YellowKnife System before? I cant even seem to find pictures of it on the web sadly...

I highly recommend people click on the "documentation" tab in the link i provided, and reading the PDFs there :)
 
  • Like
Reactions: AphoticD

AphoticD

macrumors 68000
Feb 17, 2017
1,967
2,594
Australia
Introducing the only online image of the YellowKnife X4 Evaluation System. Restored in full glorious Beige (with yellow hints) from the B&W print in the user manual :cool:

YellowKnifeBox.jpg


PC Design in the 90s was so exciting. Just look at that arc in the front grill. For some reason Seaquest DSV comes to mind.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.