QS CPU into Gigabit- two questions

Posted by: the_anarch

QS CPU into Gigabit- two questions - 01/29/09 09:24 AM

I know it's been done before, and I've found a number of websites that detail what exactly is needed to be done (most importantly the 12v to the fourth post). The two questions I've had difficulty finding the answer to (and yes I've searched these boards, and others) are:

1- When I remove the ATAPI connector for the optical drive from the front of the motherboard to make room for the QS daughtercard, can I then get a longer IDE cable and use it to connect both the optical drive and the hard drive to the hard drive's IDE connector? Or is it unavoidable, when putting a QS CPU onto a Gigabit board, that the machine will no longer have a functioning internal optical drive?

2- I've found the instructions on soldering jumpers on the back of the QS daughtercard to take it back closer to it's original speed rating (e.g. changing the 5.5 multiplier of a 733MHz CPU to 7.5, so that on the Gigabit's 100MHz bus it'll run at 750MHz). What I haven't found is how to do the motherboard modification so that I can bump it up from 100MHz to 133MHz, and either leave the daughtercard jumpers alone or overclock it slightly.

I believe I saw on these boards that someone named Antonio has done or knows how to do the motherboard 133MHz mod. Maybe you could help?

Thanks everyone for having me
Posted by: dbculp

Re: QS CPU into Gigabit- two questions - 01/31/09 07:02 AM

Some people who have tried overclocking G4 motherboards have reported that the PCI slots don't work. Anyway the bus speed probably won't bottleneck your machine unless your processor is faster than 1.5 GHz.
Posted by: Waragainstsleep

Re: QS CPU into Gigabit- two questions - 01/31/09 01:48 PM

If you can make an IDE cable fit, you can run an optical drive as the slave if you like. Or the master. Old G4s can be a bit fussy about bootability and jumper settings. Some will not boot from slave optical drives. Others may not boot from any slaves. You will have to do some testing, but you should be able to get a bootable HD and readable optical in some configuration at the very least. You might consider moving the HD to the zip bay to make it easier.
Posted by: the_anarch

Re: QS CPU into Gigabit- two questions - 01/31/09 11:03 PM

You know, I thought I remember reading on some other site that the Gigabit mobo overclocking doesn't always get you 133MHz, sometimes it's more like 115(?). So dbculp, I guess it's your opinion that with the other PCI slot potential problem, it's not worth it just for a 33% gain in bus speed when the processor isn't going to push it that hard anyway.

I probably won't mess with it and will just overclock the daughtercard. Anyone else have an opinion on (or the instructions for) the motherboard upclocking procedure?

As for the optical drive, thanks for the advice WAS- I have a lot more experience in the old SCSI voodoo than IDE tomfoolery, but with only two drives, no IDs and no terminators it's not that complicated to try out. I will have to leave the HD where it is though, part of the mod necessary for putting a QS daughtercard into a Gigabit is that apparently one must use the original QS heatsink, which requires cutting away part of the Zip drive carrier with tin snips.
Posted by: Waragainstsleep

Re: QS CPU into Gigabit- two questions - 02/03/09 11:39 AM

Have a look on this site:

http://power-mac-g4.com/g4clockup.html

I only glanced at it but it might have the jumper settings you need.

I have heard that certain G4s are prone to instability when the bus is OC'ed.
Just remember if you do it, it will push the CPU speed up even further, so if you have the CPU OS'ed already, you could melt it if you don't clock back down to do the bus.
Posted by: dbculp

Re: QS CPU into Gigabit- two questions - 02/16/09 02:37 PM

Quote:
You know, I thought I remember reading on some other site that the Gigabit mobo overclocking doesn't always get you 133MHz, sometimes it's more like 115(?). So dbculp, I guess it's your opinion that with the other PCI slot potential problem, it's not worth it just for a 33% gain in bus speed when the processor isn't going to push it that hard anyway.

That's my take on it. You know, a lot of the 933 MHz G4 CPUs being sold on eBay these days are just oc'd 733 processors. Instead of messing with the mobo bus speed why not take a chance and set the CPU resistors for 9x, clean off the black goop Apple uses on the CPU and heatsink, apply a high quality thermal compound (I use Arctic Silver Ceramique) and see what happens????