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eMac 800Mhz -> 1.33GHz conversion

I don't have answers to several of your questions I'm afraid. I went out and bought my 800 almost immediately after they came out, so I'm at a bit of a loss as to why some seem to be ready for a 133mHz FSB (replete with PC133 RAM as opposed to PC100) and others are missing that chip altogether.

Nor can I answer about the glitches at higher speeds. You are correct that higher FSB/lower multiplier is usually more stable, at least in PC's. The first thing I'm going to do is move the multiplier down to 7x and bump the FSB to 133mHz. That's still going to be a higher speed than where I'm at now though, which is 900mHz, up to 933mHz.

I'll be able to verify what's mounted where under the sodimm this afternoon. I have a silly question though: the only thing I ever use my multimeter for is continuity testing. I know, I know, that's still, but it's true. Can I test resistance using that? :p I'm a network engineer, not an electrical one.
 
How about the 700mHz iMac ?

Ok. I am not a techie and I am a little lost. I have a 700iMac and would like to know : is there a way to overclock it higher as well?

thanks,
davida
 
I'm not sure. You'll need to look at your motherboard. Look to see if it's the same board as the one in my pictures. If it is, then check the multiplier registers and compare them to my table. If they match, then finally check to see if the clock chip is there. If it is, then more than likely it can.. :)

I'm sitting at 9x multiplier and 100mHz FSB right now, or 900mHz. This evening I'm hoping to try 7x multiplier and 133mhz FSB, which is 933mhz.

In theory (no way to know if the cpu supports it or not) the iMac has the same range and tolerances as the eMac, giving us 1.4Ghz. Actually, that clock chip allows for a 150mHz
FSB, and a 10x multiplier is possible, giving us 1.5Ghz, but without outboarding the SuperDrive to an external firewire enclosure, and possibly using a peltier cooler, I'm not sure this will be possible.

But to show you my persuasion, I already have the external enclosure lying in wait and some links to peltier coolers in my bookmarks. ;)
 
Just tried to push my 1.33GHz eMac's FSB to 140MHz and it did not boot at 1.4GHz at all. Just was beeping and blinking its LED. I think the memory did not pull it off. Well I do not object. It "almost" works on1.4GHz at 133MHz FSB (hangs after 10-15min under heavy load). So most probably it is the memory issue.

By the way I have initially used 10kOhm resistors instead of shorts and ended up with a 100MHz FSB (=all three jumpers removed) so basically it is what 700 and 800MHz non-ATI eMac are. This is just proves that to get 100MHz->133MHz you need to short circuit R303 - do not bother soldering a resistor there (I have removed it, then accidentally lost it and ended up simply shorting it with some extra solder.)
 
You rock Leo!

Whoo~hoo~

Once again, thank you! I'm glad I got to be part of this exciting discovery.
 
Cypress has replied back with the pinout for eMac. As Leo has already pointed out, it is indeed the chip!

Unfortunately, it is too big to attach. Would anyone willing to host it? *cough* Numbski *cough* :D
 
I have made iMac's 800MHz logic board scans. Click on the icons to see full-size pictures. It features my wallet as a prop. :p



Anybody willing to host them?
*cough* Numbski *cough*
*cough* bigbadmac *cough*:D
 
Does anybody have any idea of what unpopulated connectors could be?

This huge 140 pins J23 looks like it is sitting right on the system bus. Since it is on the bottom of the board I assume it is for preproduction samples testing only unless Apple plans to use this logic board in a ball shaped Mac :)

Experience shows that unpopulated connectors could hide some goodies, like serial ports or S/PDIF digital sound output...

Also can you spot outputs for network receive, link and speed LEDs, disk activity LED and RESET and NMI switches? :D
 
If I had to wager a guess, I'd say compact flash.

I don't remember how many pins are on a compact flash interface, I'd have to go look it up.
 
Originally posted by Numbski
If I had to wager a guess, I'd say compact flash.

I don't remember how many pins are on a compact flash interface, I'd have to go look it up.
Click to expand...

Only about 50 :p click->
 
Update: eMac power switch pinout

Somebody was asking for the pinout of the power switch (J4503). I turns out it is simply a push-button. Going clock-wise from the key pin (bottom-right):

1 - Connection cable shield (thick black)
2 - no connection
3 - power on switch (red) +
4 - power on switch (thin black) -

pins 1, 2, and 4 are all grounded on the logic board
bushbutton switch is connected between 3 and 4.
 

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I've been kinda quiet. I haven't had a chance to mess with the iMac's FSB connections under the SODIMM socket. Been very busy.

Maybe this week? I'm still trying to figure out how I'm supposed to get 3 groundable pins out of 6 pairs of solder points. Leo never did clear that one up for me. :p
 
Of course, if none of us here has a G5, it's not worth much...

Although the VTech G5's are on sale for $2800 at MacMall, so if anybody wants one now...
 
Originally posted by Numbski

Need that shot to be larger and clearer...
Click to expand...

G5 CPU closeup. Is that what you are looking for? :) Obviously CPU multiplier should be located on a CPU plug-in board not motherboard itself.
 
Originally posted by Numbski Also need to find the clock chip, and the G5 (IBM 970) data sheet for what we'd need to be looking for as far as multiplier goes... [/B]
Click to expand...

Can't find anything on IBM's main site, only an overview presentation...

I don't think such a thing exists, publicly.
 
Originally posted by lbodnar
G5 CPU closeup. Is that what you are looking for? :) Obviously CPU multiplier should be located on a CPU plug-in board not motherboard itself.
Click to expand...

Bah, I had my brain in iMac land, where the cpu is on the mainboard. I was really tired when I made that post.

I need to convince my wife to let me have some iMac downtime to get my multiplier set up today.
 
iMac 133MHz -> 167MHz FSB?

Inspired by lbodnar's article, Numbski's link and discussion on this thread, I manage to overclock my iMac FP 17 inches 1G Hz to 1.27G Hz (via changing CPU's multiplier from 7.5x to 9.5x under FSB 133MHz). Here is my iMac's mainboard picture with detail location of resistor bank.

R374 R376 R378 R379 R382 ---> left column resistors on picture
7.5x + - - - -
8x - - + + -
8.5x - + + - -
9x + + + - +
9.5x + + + - -
10x - + - + +

+ : with resistor
- : without resistor

For the right column resistors R375, R377, R380, R381, R383 it is simply "inverse" of left column, i.e. For each row the resistor located either on left side or on right side.

Put in another way:
===================
According 7455 datasheet page 47,48 : CPU's Bus-to-Core Multiplier table. For example, if you want 7.5x the PLL_CFG[0:4] column is "00010" with order "Bit 5, Bit 4, Bit 3, Bit 2, Bit 1" than only "Bit 2" set to "1", That mean R374 should mount a resistor (so R375 need not mount resistor) ....

R374,R375 ---> Bit 2
R376,R377 ---> Bit 3
R378,R380 ---> Bit 4
R379,R381 ---> Bit 5
R382,R383 ---> Bit 1

My ambition is raise FSB from 133MHz to 167MHz, since higher FSB mean higher performance with same CPU speed. But without new iMac (167MHz FSB model) mainboard picture for compare, I can't go any further :(
Could someone provide or point me to these new iMac mainboard picture? Thanks.
 

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eServe

Long live eServe!
I'll do it if someone will give full instructions and a parts list.
Do you think it would be possible to use the eMac CRT monitor as a monitor if it were mounted in the original case?
Does the original type 700 Mhz eMac have dual independent ide channels like the new type 800 Mhz version? If so one of these mounted in a rack server case at around 1 GHz running with some serious cooling could basically be an eServe, albeit witha lower bus speed...
Interestingly, http://developer.apple.com/documentation/Hardware/Developer_Notes/Macintosh_CPUs-G4/eMac/eMac.pdf

notes on page 36 that the Airport card is in fact mini PCI based so, theoretically speaking, it would be just possible to get this hooked up to a normal PCI slot and run a PCI card in it, wouldn't it?
Also, would it be possible to run dual monitors by taking a feed off the internal monitor wiring as the first eMacs don't support software modification. Someone raised this already but I dunno what the answer was. This was definetly the case with the first iMacs (G3) which hooked up to the monitor with, wait for it, a VGA connector and could be made to support spanning by running a lead out from the VGA lead to a second monitor.
Anyway.
Keep it up guys! This is exciting!
 
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