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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Desktops > G4 Processor swap

G4 Processor swap
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G4Man
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Jun 22, 2001, 01:01 AM
 
Hey guys, I just need to know if a stock G4 733mhz processor will fit into or replace my G4 400mhz agp sawtooth processor? This guy is selling the 733mhz G4 processor, and I need to know for sure that it will fit or be compatible with mine. It'll give a great speed boost. I need to know asap. Thanks guys, anything would help.
www.amaesing.net
     
Paulos
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Jun 22, 2001, 05:56 AM
 
Sorry, I don't have an answer for you... but I am really curious as to why someone is selling a G4 733 processor on it's own.
     
jbell
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Jun 22, 2001, 10:17 AM
 
I doubt that the stock G4 733mhz processor would be compatible with the G4 AGP sawtooth mobo because of the 100mhz bus speed (i.e the clock speeds would be out of sync). You would need a 133mhz bus speed mobo. If you had a G4 533mhz then you should be able to upgrade to the 733mhz. However, if Apple comes out with a 800mhz (or in the order of 50's or 100's), then you may be able to upgrade your 400mhz processor.
     
Nimisys
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Jun 22, 2001, 12:53 PM
 
...that is unless you can find the FSB (Front Side Bus) control and lower them to 100mhz...at the same time you will need to raise the Multiplyer.

If you stick it in as it is now you'll have the 100mhzFSB times the 5.5 ultiplier for the board=550mhz...still an upgrade though just not as much.

If you were to raise the FSB of your 400 to 133mhz then you would have a 533mhz G4 chip... chances are this will net you more speed than the 400@550@100 becuase of the greater FSB bandwidth allowed to you. But in order to do so you would probably have to raise the Core Voltage (Vcore) so a bit stronger of cooling will be neccessary to get it to run stable.
     
zac4mac
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Jun 22, 2001, 01:08 PM
 
I have heard of a few people successfully bumping the FSB up to 133 on a sawtooth, and I don't believe it involved raising core voltage or RAM signal levels(bias). There have been some problems tho, which is why I didn't try it. Not to mention having to upgrade RAM from PC100 to PC133. Check at www.xlr8yourmac.com for more details, specifically anything from Michiro Isobe. I settled for a .5x boost on the multiplier for my DP500. It's been running stable at 550 since December 2000.

Zack
     
G4Man  (op)
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Jun 22, 2001, 01:23 PM
 
Originally posted by Paulos:
<STRONG>Sorry, I don't have an answer for you... but I am really curious as to why someone is selling a G4 733 processor on it's own.</STRONG>
This guy I know works at a Mac store, and someone had sold there G4 733 tower as parts, so I'm just interested in the processor alone. Well thanks guys for the info. I might just buy it and try it out, but will it cause any problems for my computer, or I can just switch back to my original processor, and things would be fine again, if the 733 processor didn't work.
     
reader50
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Jun 22, 2001, 04:53 PM
 
My guess is that it would work. The daughtercard socket on the motherboard is the same, the card should plug in. As others have said, it will boot up at 550 MHz though. To go higher, you have two options. You could increase the FSB speed as others have said. That would involve soldering work on resistors on the underside of the motherboard, tweaking the firmware, and RAM upgrades to 133 as needed. The other & easier option is to change just the multiplier on the CPU card, you could shoot for 700 or 750 MHz. This will still involve fine soldering work on the CPU card, but no RAM changes or firmware tweaking. We hope.

The backside bus speed is set in software, and should be 1/3 of the processor speed for this card. Since your Sawtooth system's backside bus is set to 1/2 the CPU speed by default, I suggest you drop it to 1/3 before changing the multipliers. Otherwise, you would be trying to boot the new card with the L3 cache running around 50% faster than it is set for at the factory. I recommend the XLR8 Mach speed control software.

Also, the 7450 chip runs hotter than the 7400. You will need the heatsink/shroud/fan that it came with. And you will need to plug that fan in. I do not remember a fan connector on the Sawtooth motherboard, so you may need to steal power from a spare disk drive power connector.

This is just guesswork here of course. But I would try it. First at 550 (no mods yet), then at 750 if it booted OK at 550. After all, at worst you will be out the $1,000 you paid for that 733 CPU card.

[ 06-22-2001: Message edited by: reader50 ]
     
Nimisys
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Jun 23, 2001, 03:05 AM
 
Originally posted by zac4mac:
<STRONG>I have heard of a few people successfully bumping the FSB up to 133 on a sawtooth, and I don't believe it involved raising core voltage or RAM signal levels(bias). </STRONG>

Raising those are standard Ocing tricks to gain higher, stabler speeds, that why i suggested them. Not sure on the MAC, but on the PC side of things, PC133 is backwards complaint with 100 busses... and 100 Buses are complaint with 133RAM, even though it only runs at 100mhz. unles there are microcode changes, a BIOS update won't be neccesary.
     
zac4mac
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Jun 25, 2001, 08:54 AM
 
I was seriously considering pushing my Mytsic to 120 or 133 FSB. Info from M. Isobe said no firmware tweak needed for sys clock and motorola documentation looked good for 120, fuzzy at 133. I even got some PC 133 RAM in preparation. Didn't want to forsake the stability for a little more speed, 550 x 2 is pretty fast.
You're right tho Nimisys, the proc core voltage can be bumped and so can the L2 and RAM signal level... if you're bold. They are already close to the top and I have read of a couple of folks that fried their processors, trying to add one or two tenths of a volt. Maybe they needed supercooling.

G4Man, you'd do better looking for a duallie board, IMO.

Zack
     
<no_name_1>
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Jun 29, 2001, 08:18 PM
 
It won't work. The processor card on the 733 is rectangular, and the connector is on the wrong long side of the rectangular card to fit into a Sawtooth because the ATAPI IDE connector is in the way. Also your heat sink will probably not fit right. Also there's probably not enough cooling. Also the firmware won't support it. Also the your OS needs to be able to support it.
     
   
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