Overclock the 133 MHz bus on the Dual 867?

onemoof

macrumors member
Original poster
Jul 23, 2002
75
0
Minneapolis, Minnesota, USA
Assuming that the Dual 867 uses the same mobo as the other PMacs wouldn't it be easy to clock the bus back up to 166 MHz? I assume it's probably just downclocked to sell people up to the midrange.
 

mc68k

macrumors 68000
Apr 16, 2002
1,996
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Re: Overclock the 133 MHz bus on the Dual 867?

Originally posted by onemoof
Assuming that the Dual 867 uses the same mobo as the other PMacs wouldn't it be easy to clock the bus back up to 166 MHz? I assume it's probably just downclocked to sell people up to the midrange.
"Easy" assuming your comfortable with voiding the warranty and have good soldering skills. You can overclock any 133 bus mac to 166 relatively easy. Go to the tweaking and case mods section of xlr8yourmac.com.
 

sparkleytone

macrumors 68020
Oct 28, 2001
2,309
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Greensboro, NC
im somewhat sure that its just a jumper setting. screw the warranty, buy it at compusa and get their warranty. it covers it. if you are gonna screw with your computer hardcore, buy it there and get the service plan.
 

GeeYouEye

macrumors 68000
Dec 9, 2001
1,653
4
State of Denial
Correct me if I'm wrong, but doesn't increasing the bus speed make the clock go too fast (ie overclocking 100-133MHz makes the clock rollover 1 minute every 40 secs)
 

mc68k

macrumors 68000
Apr 16, 2002
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Originally posted by GeeYouEye
Correct me if I'm wrong, but doesn't increasing the bus speed make the clock go too fast (ie overclocking 100-133MHz makes the clock rollover 1 minute every 40 secs)
Bus x Clock multiplier = CPU speed

Overclocking the bus overclocks the components in the system, too.
 

Sepulchre

macrumors member
May 27, 2002
74
0
UK
Originally posted by mc68k
Bus x Clock multiplier = CPU speed

Overclocking the bus overclocks the components in the system, too.
So if I understand this right the 867 chips will end up running at a little over 1GHZ?

Pass me the soldering Iron :D

But then would the PC2100 Ram be to slow?
 

mc68k

macrumors 68000
Apr 16, 2002
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Originally posted by Sepulchre
But then would the PC2100 Ram be too slow?
No. You can upclock the old PC133 busses to 166 and it still recognizes the mem fine. Same with my old mac's 50 mHz bus. No problems there. The 2100 RAM is on a different bus than the system bus.
 

Sepulchre

macrumors member
May 27, 2002
74
0
UK
Originally posted by mc68k

No. You can upclock the old PC133 busses to 166 and it still recognizes the mem fine. Same with my old mac's 50 mHz bus. No problems there. The 2100 RAM is on a different bus than the system bus.
So why does apple spec the PC2700 for the 166 bus and PC2100 for the 133 bus, just to get the most performance out of it?
 

ddtlm

macrumors 65816
Aug 20, 2001
1,184
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mc68k, Sepulchre:

Speaking from experience with overclocking PC's, Apple's busses may or may not need to be synchronised (and they could have changed that from the SDR to the DDR chipsets).

They may require the synch because it lowers latency vs asych operation, as was pretty much shown by VIA's KT133A and KT133 chipsets. Both used PC133 RAM and a DDR FSB, but the one that used a FSB running at 133x2 instead of 100x2 had a significant performance edge... and remember that in both cases the PC133 RAM was far slower than the FSB so the extra FSB speed in itself should have amounted to nothing.

A lot of DDR-266 will make it to DDR-333 speeds, but you can not be sure yours will, and the more of it you have loaded in your machine the harder the OC becomes. I'd recommend getting some real DDR-333 from a reputable manufacturer.

Also, you may find that your G4 chips cannot clock 33% higher, or that the L3 caches cannot do it. You are looking at a lot of components here that all need to make it, and I am sceptical about your odds. Changing the multiplyers of the G4's down would be a good idea (presumably more soldering).
 

firewire2001

macrumors 6502a
Apr 2, 2002
718
0
Hong Kong
Originally posted by Sepulchre


So if I understand this right the 867 chips will end up running at a little over 1GHZ?
will his computer really be 1082.12030075187969924812030075188 mhz, mc68k?

dang.. thats fast...
 

topicolo

macrumors 68000
Jun 4, 2002
1,672
0
Ottawa, ON
Jeez, you guys are such o/c newbies (except you ddtlm. You seem to know what you're talking about. What have u got there? a watercooled rig? a peltier?) Try visiting some pc o/c sites like [H]ardOCP and you'll learn a LOT. (a lot of the theoretical stuff applies to macs too.)
 

bousozoku

Moderator emeritus
Jun 25, 2002
13,951
3
Gone but not forgotten.
I would be concerned that these 867 MHz parts have already been tested at 1 GHz and failed and could only be tested successfully at 867 or maybe 900 (which isn't on the menu).

If you stress them beyond reliability, it would be expensive to replace them both and associated components like the L3 cache. SRAM is still hugely expensive.
 

mc68k

macrumors 68000
Apr 16, 2002
1,996
0
Originally posted by firewire2001


will his computer really be 1082.12030075187969924812030075188 mhz, mc68k?

dang.. thats fast...
Yes, take a look at this page.
 

mc68k

macrumors 68000
Apr 16, 2002
1,996
0
Originally posted by topicolo
Jeez, you guys are such o/c newbies (except you ddtlm. You seem to know what you're talking about. What have u got there? a watercooled rig? a peltier?) Try visiting some pc o/c sites like [H]ardOCP and you'll learn a LOT. (a lot of the theoretical stuff applies to macs too.)
Thanks, but no thanks. I only do overclocking through the dips on my XLR8 card. As for soldering/desoldering things, that's not my cup of tea. I've got better things to do w/my time. :rolleyes:
 

Dr_Floyd

macrumors member
May 27, 2002
41
0
"im somewhat sure that its just a jumper setting. screw the warranty, buy it at compusa and get their warranty. it covers it. if you are gonna screw with your computer hardcore, buy it there and get the service plan."


yeah but you go thru hell gettingcompusa to live up to the warranty they sold you. Their money comes from selling you this high priced warranty, they stall and try to keep you from using what you paid big money to buy.

In other words don't get teh comp "TAP"
 

sparkleytone

macrumors 68020
Oct 28, 2001
2,309
0
Greensboro, NC
heh that all depends on your individual store manager. my store was really awesome about it so it made my job as a salesman much easier. if they give you sh*t, just call the corporate office and bitch until they call the local store. it works i promise.

plus the TAP on laptops is priceless.
 

Sepulchre

macrumors member
May 27, 2002
74
0
UK
Originally posted by topicolo
Jeez, you guys are such o/c newbies
I feel I must apologies for being such a Virgin at this Over clocking subject, as I have never found then need to over clock my Mac it is not a field in which I have ever sought to increase my understanding.

However as the base G4 is on a 133 bus compared to the 166 buses of the other Macs I thought this might prove an interesting topic and a cheap upgrade to an intentionally limited system.

Again, excuse my naivety in this field and accept my apologies for asking what MUST be considered a stupid question to such pro's we have here!

Warning - all sarcasm herein is intentional!
 

Dr_Floyd

macrumors member
May 27, 2002
41
0
It has nothing to do with the store, the corp. level at Comp and their TAP is the problem. TAP=Waste Of Money
 

bousozoku

Moderator emeritus
Jun 25, 2002
13,951
3
Gone but not forgotten.
Originally posted by Dr_Floyd
"im somewhat sure that its just a jumper setting. screw the warranty, buy it at compusa and get their warranty. it covers it. if you are gonna screw with your computer hardcore, buy it there and get the service plan."


yeah but you go thru hell gettingcompusa to live up to the warranty they sold you. Their money comes from selling you this high priced warranty, they stall and try to keep you from using what you paid big money to buy.

In other words don't get teh comp "TAP"
Isn't that the truth?

I had to fight with the Apple certified tech. at CompScrUSA to have a bad iMac modem replaced because "it's a phone line problem" even after I told him that I used another Mac on the same line and it worked fine.

He did it after all and everything works fine now. The charges for the modem, the CMOS battery, and the labour were over $300, which is hard to believe. I believe the TAP was $249.