eMac 800Mhz -> 1.33GHz conversion

[jspivack]

schematic?

Here is Gen1 eMac (700MHz) running without downconverter board. I have combined 2.5v LM317 regulator and a DCB connector together on a small breadboard. They are just regularly spaced jumper pins. Blindmate connector still needs 12v and 5v supplied to it.

Leo - this rocks! looks like I've got a plan for my easter weekend...

would you mind sketching out and posting a quick schematic of your "homebrew" DCB? Also, what's that molex connector in the upper-left hand corner of the first picture connected to?

thanks so much
Jeff

 

[rmanger]

1.25GHz to 1.5GHz Overclock Successful!

I've done it! I've overclocked my Gen3 eMac to 1.5GHz!

Here's some real-world results for you folks out there. I tested using Unreal Tournament 2004 v3355, measuring average FPS using the Santaduck benchmark.

The test hardware is:

1GB RAM
Radeon 9200 w/ 32MB VRAM
MacOS 10.3.8

The test config is:

Gametype: Botmatch
Map: DM-Antalus
Resolution: 640x480
Graphics: Minimum settings

Avg. FPS @ 1.25GHz: 36.43 FPS
Avg. FPS @ 1.5GHz: 39.62 FPS

Overall Speed Increase: 8.76%

I thought I'd get more FPS, so it leaves me a bit disappointed. However, the difference in visual speed was noticeable enough that I could say it is not a placebo effect, especially at the speedier parts of the test.

Unfortunately, the FPS at 1.5GHz is still processor bound. Overclocking the 9200 using ATIccelerator II showed no improvement in FPS.

Some good news: XBench doesn't crash my eMac at 1.5GHz.

I also tried overclocking at 1.67GHz and 1.75GHz, but neither worked. In fact, the eMac didn't start up at all, not even making the startup sound.

Also, it seems like the Gen3 eMacs have the same voltage control chip as the Gen2 eMacs. lbodnar, do you think that increasing the Vcore voltage would let me get these higher speeds? Or is this just a case of my processor reaching its limit?

 

[lbodnar]

would you mind sketching out and posting a quick schematic of your "homebrew" DCB? Also, what's that molex connector in the upper-left hand corner of the first picture connected to?

I recommend using ready made ATX motherboard power extension like this one. It is cheap, prewired and colour-coded. Pinout can be found here.

Both resistors must have the same value.

Capacitors on LM317 in/out pins are not necessary but if you wish, anything from 0.1uF to 100uF will do (from IN to Gnd and from OUT to Gnd).

Molex connector is connected to blindmate connector - you still need to supply 12v and 5v to it as described here.

Green wire is ATX power_on, it turns ATX PSU on when grounded. I meant to connect it to some sort of a switch. I am not sure if eMac can control PSU as I still think it needs more then just trickle 5v to power up. Meanwhile this is work in progress...

Correction to the diagram: there are four +5v wires on ATX connector, not two...

 

[madmaxmedia]

G3 jumpers!

Hey Leo,

Thanks so much for posting the G3 eMac jumpers! I have one of the educational 1 GHz eMacs ($549 from Apple.com), so going to 1.5 will make a great difference for me...

Thanks again!!!
Steve

 

[lbodnar]

I am really interested to see how far Gen3 eMacs can go!

...By the way this thread has become the most viewed one in hardware forum. We must have generated some interest! The thread has accumulated so much unique eMac-related stuff that I start to think it could be a good idea to locally archive it to a CD. If you remember we totally lost Gen1 overclock guide until BigBadMac rewrote it himself again.

 

[rmanger]

Now running at 1.58GHz!

Yes! Now my Gen3 eMac is running at 1.58GHz!

And it displays the correct information in the About This Mac menu!

Getting my eMac to this level was definitely an adventure. I had to up the Vcore to 1.450V to get the eMac to work. Here's some data:

1.25GHz, 1.350V (Original Settings): Works stable

1.5GHz, 1.350V: Works stable

1.58GHz, 1.350V: Kernel panic on startup
1.58GHz, 1.450V: Works stable

1.67GHz, 1.350V: No startup
1.67GHz, 1.450V: Kernel panic on startup
1.67GHz, 1.475V: Kernel panic on startup
1.67GHz, 1.500V: Works, but unstable
1.67GHz, 1.550V: Works, but unstable

From the data, it seems like 1.5GHz is the maximum clock speed one can achieve at the original 1.350V setting. Higher clock speeds can be achieved by increasing the Vcore voltage. This supports what lbodnar said in a previous post. Also, 1.67GHz @ 1.500V was a little more stable than 1.67GHz @ 1.550V. This is probably just a heat issue, so anyone who got a better processor than me could probably get 1.67GHz.

So was all that work for that extra 80MHz worth it? I used UT2004 again with the same config as before, and here's the results:

Avg. FPS @ 1.58GHz: 40.56

Overall Speed Increase (from 1.25GHz): 11.34%

 

[lbodnar]

Yes! Now my Gen3 eMac is running at 1.58GHz!
And it displays the correct information in the About This Mac menu!

...without nvram patch?

Thank you for very detailed information, rmanger!

Does anybody know if Gen3 eMacs use 7447A or 7447B CPU?

 

[MrFX]

Hi again,

Leo, have you tried to power the CPU with 5V?

I can get a cheap, little PSU, which has a 5V output of 18A an 12V only 3A.

See you...
MrFX

 

[lbodnar]

CPU power from 5v

Leo, have you tried to power the CPU with 5V?

Yes, I did. I also thought that it might be easier on some PSUs so I tried and it works just as good as 12v. I can see no difference. The controller chip is specified for operation in 4.5...14v range.

 

[rmanger]

No nvram patch required!

...without nvram patch?

Nope, I didn't need to patch anything. The system just recognized the processor speed automatically!

 

[vga4life]

So, has anyone started on an eMac ATX conversion yet? I notice the size, unusual configuration, and strange shape of the emac logic board probably require a full-size ATX case with ultra-tall standoffs (probably homemade with screws and tubing or nuts).

I'm waiting for my financial situation to stabilize a bit before plunging in but I can't wait to remake my mild-mannered 3G eMac into a dual-LCD, triple-HD, dual-layer superdrive-equipped monster.

-vga4life

 

[lbodnar]

So, has anyone started on an eMac ATX conversion yet? I notice the size, unusual configuration, and strange shape of the emac logic board probably require a full-size ATX case with ultra-tall standoffs (probably homemade with screws and tubing or nuts).

I'm waiting for my financial situation to stabilize a bit before plunging in but I can't wait to remake my mild-mannered 3G eMac into a dual-LCD, triple-HD, dual-layer superdrive-equipped monster.

I am casually looking for an old DVD or CD player with nice not-busy fascia to host eMac. Disk slot will be already there!

Also if done properly and the case is made of steel, CPU heat can be directed via a block of copper to the player's case base.

I have not seen this published anywhere yet, so I will mention that eMacs use ATA-4 on HD connector and ATA-3 on CD drive connector (even without the CD drive attached) so the third HDD on this bus will have pretty low data peak transfer rate - around 10MB/sec as opposed to two others on ATA-4 (I have around 30MB/sec there).

Looks like ATA-4 speed is limited by drives themselves but with ATA-3 it is bus-restricted...

 

[topgunn]

I have not seen this published anywhere yet, so I will mention that eMacs use ATA-4 on HD connector and ATA-3 on CD drive connector (even without the CD drive attached) so the third HDD on this bus will have pretty low data peak transfer rate - around 10MB/sec as opposed to two others on ATA-4 (I have around 30MB/sec there).

Looks like ATA-4 speed is limited by drives themselves but with ATA-3 it is bus-restricted...

I cannot recall the setup on my 2G eMac but I am 100% certain that the 3G eMacs use an ATA-6 bus for the HDD on the CPU side and an ATA-3 bus for the optical drive.

ATA3 = up to 33mb / sec.
ATA4 = up to 66mb / sec
ATA5 = up to 100mb / sec
ATA6 = up to 133mb / sec

 

[netjosh_granada]

So, has anyone started on an eMac ATX conversion yet? I notice the size, unusual configuration, and strange shape of the emac logic board probably require a full-size ATX case with ultra-tall standoffs (probably homemade with screws and tubing or nuts).

I'm waiting for my financial situation to stabilize a bit before plunging in but I can't wait to remake my mild-mannered 3G eMac into a dual-LCD, triple-HD, dual-layer superdrive-equipped monster.

I'm already planning a great case mod with my 1G eMac and a 2nd hand Power Macintosh 8500 tower I've bought on eBay.

I've always been a fan of old-school Power Macintosh's design and I'm planning a complete internal reestructuration of this Powermac 8500, but keeping it's great external design.

The computer I'm planning will be as follows:

• Power Macintosh 8500 tower.
• eMac 1G 700 Mhz@1000 Mhz (if possible...).
• 512 Mb PC100 SDRAM (PC133 if I manage to overclock FSB).
• LG 16x Dual Layer DVD Writer.
• Iomega Zip 250 drive SCSI (comes with PM8500 -> needs SCSI to USB/Firewire adapter).
• 2 x 80 Gb HDs in RAID 0 mode.
• 300 Watt ATX Power Supply.
• 2 x 8 cm fans running at 7v or even 5v (i'll see) on the top of the case (where ATX PSUs usually goes) to keep everything cool.

To cool the CPU, I plan to use a standart Pentium 4 heatsink (see Arctic Cooling) but adapted (cutted and drilled in certain areas) so that it can be used in this strange motherboard.

Well, I will keep you informed on this project as soon as the PowerMac comes, and as soon as Lbodnar finishes the GREAT JOB (Thank you leo ) he has made powering up my emac mobo in a way I would have never thought possible (I'm talking about running it without DCB...).

See you all...

** NetJosh **

 

[jspivack]

Homebrew DCB components - confused...

hi Leo

So I'm going to the electronics store this afternoon to pick up components for my replacement DCB so I can power my Gen1 eMac from ATX PSU only, bypassing the Apple DCB and powering the drives from the ATX PSU.

In the initial board schematic, you show 2 capacitors and 2 resistors; these are also shown in the photo.

In the second version, the schematic shows 2 resistors 0 capacitors, while the photo shows 2 resistors and 1 capacitor.

so, uh, which one is right? The documentation from NatSemi (attached) seems to indicate that one or both of the caps are optional...

thanks
jeff

 

[jspivack]

firewire power from ATX PSU + homemade DCB?

Post #371:

By the way can anybody quote definite Firewire standard on cable power? I have seen anything from 8v to 38v and even ridiculous quotes like 1.5A at 40V (that's 60w of power!) Macs traditionally supply around 15v..18v on their Firewire cable but I try to get lower to something like 11V by using only 12v PSU voltage. Portable drives and iSight are OK with that but I really want to see a standard figures...

Post #387:

yes, yes, Yes!

We can throw downconverter board away. eMac will run without it!

I have temporarily tapped in power by soldering directly to the reverse side of DCB connector on the logic board and it powers up and works! My impromptu 5v->2.5v converter (see post number 379 above) gets pretty hot so I might use a better heatsink in the final version but schematic will stay the same (I have used LM317T - can't remember how it is different from LM317A or LM317, was it Vout precision?)

I supply +12v, 5v, 3.3v off a standard 120W ATX power supply.

Leo

does your headless version have powered firewire? if so, are you getting it from ATX PSU? How are you patching it in?

thanks

jeff

 

[jspivack]

Leo

I tried making my own replacement DCB for Gen1 eMac this weekend, but it isn't quite working:

I followed your schematic from post #404, with R1=R2=470 ohms.

without load, I get 150mV on pin 13 and 4.5V on pin 11 rather than 2.5V on each one. Any ideas why that might be?

Thanks

Jeff

 

[jspivack]

without load, I get 150mV on pin 13 and 4.5V on pin 11 rather than 2.5V on each one. Any ideas why that might be?

Thanks

Jeff

I figured this out - i must have misinterpreted your schematic or something - you need to put R2 across pins Vout and Adj of the LM317. So that's OK. My homemade DCB has all of the correct voltages as indicated in schematic of post 404.

But the eMac is not powering up. (Gen1/800Mhz)

I have an ATX PSU hooked up to my homemade DCB, plus am powering the drives directly from the PSU. I've got a switch on the green wire of teh PSU to turn the PSU on and off. The main power switch on the eMac is busted, so I attached a couple of wires to try to turn the mobo on and off - but I'm not sure of the wiring there, so it's a bit of a shot in the dark.

And it's not powering up.

I have nothing connected to either of the blind-mate connectors, and nothing connected to the video connector. does anyone have any ideas?

Oh - when I got the computer, it was dead. the problem was allegedly with the analog board, but I can't rule out that it's the mobo that's dead.


thanks

jeff

 

[Tim Deh]

With much thanks to BigBadMac, my eMac works again!

Hi,

I have the same problem as you, but I can't find your solution in this thread.
I've oc'ed my eMac 700Mhz to 850Mhz (removed 1 jumper). When I reboot, I only can hear the 'chime', monitor "starts up", but no video signal.

I've already reset the Pram, removed battery,...Etc

Can you post your solution please?

 

[gothicspikey]

emac graphics question..

firstly, thank you leo for ur great guide i'm now running my 800 emac at 1.33ghz , but i have a question regarding graphics on the emac

On most PC's i've seen onboard AGP graphics use system memory istead of having its own ram, is there any way possible to like use 256mb or whatever of ram from the system memory instead of the 32mb that the emac has? i have absolutly no idea on this matter, thats why am asking really, if it was possibly that'd be so great lol

thanx in advance

 

[Plastic Chicken]

Hi,

I have the same problem as you, but I can't find your solution in this thread.
I've oc'ed my eMac 700Mhz to 850Mhz (removed 1 jumper). When I reboot, I only can hear the 'chime', monitor "starts up", but no video signal.

I've already reset the Pram, removed battery,...Etc

Can you post your solution please?

Give me your email address...I'll forward stuff to you.

I'm surprised this thread is still alive

 

[vga4life]

On most PC's i've seen onboard AGP graphics use system memory istead of having its own ram, is there any way possible to like use 256mb or whatever of ram from the system memory instead of the 32mb that the emac has? i have absolutly no idea on this matter, thats why am asking really, if it was possibly that'd be so great lol

What you're describing is not desirable. "More video ram" doesn't make the GPU faster. First, onboard video controllers that steal system ram are way, way slower than GPUs with dedicated RAM. Second, the whole point of AGP is to provide a fast pipe from system memory to video memory. In a sense, your emac is already capable of using, when necessary, system memory. This is better than the GPU being required to use (much slower) system memory.

-vga4life

 

[gothicspikey]

lol

thanx for clearing that up for me

 

[netjosh_granada]

G1 eMac Success!!!!!!

Hello everybody,

as you might know, I sent lbodnar my G1 emac motherboard to see if he was capable of making it work. He did a great job powering it up, and a couple of weeks ago he sent it back to me.

Now, I'm proud to tell you all that I've broken the Gigahertz barrier with my 700 Mhz eMac, and most important, at STOCK VOLTAGE. One of the things I've had to change is the stock cooler, and now I'm running it with a Pentium 4 All-Copper Heatsink and a 80 mm fan running at only 5v, wich is all it needs to stay cool even running Folding@Home 24/7.

I'm finishing my case mod for it, and as soon as I finish it, there will be some pictures here to let you see my eMac system.

 

[gothicspikey]

here i go again...

right i know this may sound completly stupid, but is it possible to change the L2 cache at all, the cache on my emac is 256, but i think on the new emacs the cache is 512, just wondering if it was possible, and if so how would u do it?

thanx xx