HOWTO overclock intel imac mini core etc.

[khmann]

Yeah, so perhaps you've noticed that google turns up nada... so overclock intel apple imac macbook pro mini CAS latency timing performance enhancement tweak TCL TRAS TRCD TRD here ya go.

 

Other than macpro, current units are all basically laptop, CPU is mobile T7200, T7400 or T7600, i945PM chipset with ICH7 northbridge or whatever. CPU is multiplier locked from intel.

 

options for overclock-

 

1: adjust PLL for higher FSB (stock is 166MHz, which is i945 max rated). Too much work, bad for warranties.

2: change CPU, sure any socket 469 should be fine in desktop machine but also bad for warranties.

3: muck around with EFI. not yet, maybe someday.

4: increase RAM timing. YEAH BABY!

 

EFI offers no user-servicable options, but auto-configures memory timings based on SPD of DDR2-667 PC5300 modules.

 

Apple appears to be using three types of SODIMM chip modules in production units right now. 256MBs are typically Hynix. 1GB are mostly Micron D9GMH A few Samsung in 512 and 1GB.

 

I've tested a lot of modules. Hynix and Micron clock at 5-5-5-15. Samsung at 5-5-5-13, but I've seen quite a few stability problems with these modules.

 

I'm quite happily running a pair of 2x1GB Micron D9 GMH series 4-3-3-12 with reduced WTR at 667.

 

howto:

 

*** you really need to understand what you're doing here. there's not really any chance of hardware damage but you might seriously compromise the stability of your machine. if you screw up your timings, DO NOT claim warranty, just have a spare SODIMM available for "recovery" purposes. system will automatically take timings from the slowest module in the system. it can be an old crusty 256mb DDR2-400, or just pull one of your modules until you've found your ideal settings, put it back in if you screw up. ***

 

1. boot windows.

2. run a modern cpu-z to check out your current specs (memory tab shows active chipset config)

3. run spdtool and dump your modules. save a backup to a file.

4. change timings.

5. power down, reboot windows. check cpu-z to verify timings, run orthos to verify stability. benchmark using everest or sisoft.

6. repeat as necessary.

 

I tried quite a few 1G Microns and had excellent luck at 4-3-3-12-20-32. I determined parameters by looking at spdtool and thaiphoon burner dumps of PC overclocking DDR DDR2 memory modules by overclocking enthusiast gamer RAM manufacturers.

 

setting WTR to 6ns from 7.5ns = -1 CLK produced a 400MB/s improvement in everest and seems perfectly stable.

 

SPD information contains quite a bit more than memory access timings. make sure any dump you load to a module is for the same size (256m, 512m, ) and the same geometry - rows, cols, etc.

 

hope this information is of use. I'll post more specific timing details later in my free time.

-kh

 

now will someone please figure out how to change radeon X1900 clocks in OSX? PLEASE?

[khmann]

modules:

mt16htf12864hy-667d3 200633 (singapore)

1gb 2rx8 pc2-5300s-555-12-e0

1gb, ddr2, 667, cl5

mt 6nd22 d9gmh t3db

 

stock timing:

FSB TCL TRCD TRP TRAS TRC TRFC TRRD TWR TWTR TRTP

333 5 5 5 15 20 35 3 5 3 3

 

my timings:

333 4 3 3 12 20 32 2 4 2 2

TCL, TRCD, TRP, TRAS, TRC verified by CPU-Z.

OS/X is absolutely rock solid and windows stress test "orthos" run for hours, no issues.

settings have shown stable on a number of similar modules in a number of macs.

 

Windows RAM benchmarks (everest under miniPExt)

Read (MB/s) 4795 > 4921 = +2.6%

Write (MB/s) 1148 > 1425 = +25% (wow

Latency (ms) 97.9 > 88.3 = 11% faster

 

hopefully read performance can be furthur enhanced, unless CPU FSB (166MHz) is the bottleneck. Most likely changes would be TRAS+friends (TRC=TRAS+TRD, TRFC). Too small TRAS reported to give worse performance, and stability problems.

 

 

SPD:

00000000 80 08 08 0e 0a 61 40 00 05 30 45 00 82 08 00 00 |.....a@..0E.....|

00000010 0c 04 18 01 04 00 03 3d 45 00 00 24 18 24 24 80 |.......=E..$.$$.|

00000020 20 27 10 17 30 18 18 00 00 3c 60 80 18 22 00 00 | '..0....<`.."..|

00000030 00 00 00 00 00 00 00 00 00 00 00 00 00 00 12 39 |...............9|

00000040 2c ff ff ff ff ff ff ff 08 31 36 48 54 46 31 32 |,........16HTF12|

00000050 38 36 34 48 59 2d 36 36 37 44 33 03 00 07 08 6b |864HY-667D3....k|

00000060 68 63 31 00 00 00 00 00 00 00 00 00 00 00 00 00 |hc1.............|

00000070 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|

 

 

SPD is for my 1GB sticks and you should NOT write it to yours without a thorough understanding.

[khmann]

a few updates...

 

my 2x 1GB Micron D9GMH in a 2.16 20" iMac (late 2006)

 

FSB TCL TRCD TRP TRAS TRC TRFC TRRD TWR TWTR TRTP

333 4 3 3 12 20 32 2 4 2 2

 

even when setting all other parameters to relaxed values,

Tcl < 4 = fail

Trcd < 3 = fail

Trp < 3 = fail

 

So 4-3-3 seems about as good as it gets with these.

 

at stock DDR2-667 speed, iMac refuses to set TRC below 20 (at least according to cpu-z 1.39) regardless of how agressively the other timings are set. thus, I am unsure how much low Tras is really helping (because I don't completely understand this stuff... maybe someone can offer guidance?)

 

changing TWr from 5 to 4 seems to be responsible for much of the write performance enhancement. A value of 3 caused minor crashing.

 

....

 

os/x feels slightly more responsive, stability is not impacted, and oh yeah, my mac is faster than yours.

 

....

 

I'd love to get feedback if anybody else is crazy enough to think about trying this, or from anybody who knows about how the intel 925 945 chipsets capabilites regarding memory clocking (TRC, et al.)

 

thanks!

-kh

[David7586]

Are these apple sticks of ram that you are using? Can you point out any brand names that also use d9gmh chips? It seems people usually buy that gskill set on newegg.com can anyone check their sticks and share what kind of chips they are? thank you!

[Dwight F]

1: adjust PLL for higher FSB (stock is 166MHz, which is i945 max rated). Too much work, bad for warranties.

Huh, what kind of attitude is that for an OC forum? I'd be genuinely surprised if the system couldn't take a minimum of 10% over stock on the FSB. So what is involved in adjusting the clock on an Intel Mini? Is it somehow handled through EFI? Or is it like the PPC Mini with jumpers soldered onto the board?

 

P.S. I don't have a Mini yet. Hell I don't own a Mac period, never have. I'm just doing some research for the wife because she's thinking of getting one.

[khmann]

Are these apple sticks of ram that you are using? Can you point out any brand names that also use d9gmh chips? It seems people usually buy that gskill set on newegg.com can anyone check their sticks and share what kind of chips they are? thank you!

for me, new machine, genuine apple. I fix other peoples macs all day long, I want no problems with mine. granted, I install generic ram every day with no issuses... when 2gb sticks become more widespread, I'll probably upgrade.

 

the 2x1gb kit seems to mostly be GMH right now, previously I think it was mostly high-end Samsung (though I've seen several that needed replacement, I have done limited testing at 4-4-4-12 with no problems)...

 

Huh, what kind of attitude is that for an OC forum? I'd be genuinely surprised if the system couldn't take a minimum of 10% over stock on the FSB. So what is involved in adjusting the clock on an Intel Mini? Is it somehow handled through EFI? Or is it like the PPC Mini with jumpers soldered onto the board?

 

P.S. I don't have a Mini yet. Hell I don't own a Mac period, never have. I'm just doing some research for the wife because she's thinking of getting one.

I've heard rumors of an undocumented 200mhz FSB support in similar chipsets from intel, so it's definately possible. Mac components seem to be very good, well binned, so it could happen.

 

Current intel iMacs have good internal heatsink on chipset and a decent heatpipe/heatsink on CPU, so knowing how well the C2D's usually overclock, things could get nutty. I don't know if it would apply in this situation (mobile cpu), but I've heard there's something about "strapping" the CPU to manipulate bus timing parameters, seeing as Apple obviously isn't going to let you adjust them via EFI (at least not without reverse engineer/modification)

 

I do not know how the PLL (if it's even that simple) is controlled, ie: shunt or software, but I'll start trying to identify clockchips at work.

----------------------

however, at the end of the day, my AppleCare protection plan is very important to me. It took some time to cough up the money to make the switch from PC, hell - I've paid less for cars, and I am well aware of what some of these units cost to repair... think $800 logic (mother) boards, $650+ displays, and then add two hours of labor.

 

if your girl gets any high-dollar Mac, especially refurbished, you're crazy not to get that warranty within the 1st 12 months. still, IMO, worth every penny.

[Dwight F]

Well the good news if I'll be doing anything for now it'll be on a Mini. Not exactly disposable, and yes I've paid less for a car. But that was over 20 years ago, I bought the car from an uncle, the car was only 4 years younger than I was, and it had body damage where my uncle had fallen asleep, drove into the ditch and down a barbwire fenceline taking about about 10 pickets. So if you do manage to piece together how to tweak the clock, or even some hints, please let me know.

 

I just priced out this morning some Value Corsair 1GB SoDIMMs that they support for the Mini Mac. Cheap like borscht, I found them online for less than $40CDN each and checking around they have had reports (relatively few of course given the types of machines these typically go into) of solid moderate OCing and tighter timing over their stock DDR2-667 / 5-5-5-15. Right now the only thing holding me off ordering a Mini, the RAM, and a 160GB HDD (EDIT: oops, and I forgot to mention the T7200 CPU to give me 64-bit capability) is finding out if I'll be able to run 64-bit Vista on it and have at least the video (I'm pretty sure that'll work), USB (not sure why it wouldn't), and NIC function.

 

P.S. Unfortunately in this case I wouldn't run this particular machine OC regularly because this would be my work machine and I need that rock solid. It'd just be to try it out a bit and stretch it's legs and a little geek cred. Not that creating a lot of extra heat in a Mini seems like a particularly good idea anyway. I will likely trim down the timings though for regular use, thanks for that info.

[cash68]

Okay, this has my interest. I have a 24" iMac with 7600GT, and I'm not new to modifying computers.... I was I think the first person to swap a 333mhz G3 daughtercard onto a rev A iMac motherboard, allowing me to use the gamewizard graphics card, .... and I did some other stuff to a quicksilver, but anyway... I have a bunch of questions, as I don't understand all this PC lingo.I am aware my iMac has a Core2Duo. When you say SOCKET69, what do you mean? When I go to pricewatch, all the core2duos are t5500-7600 or e2160 to e6150. What the hell does all that mean? Which one is in my iMac? What is compatible, if I just bought a new CPU? Also, how can intel 'lock' the multipliers? Are they impossible to unlock? This seems strange to me, in today's world of reflashing things.All this RAM nonsense you've mentioned is entirely gibberish to me, I have no idea what you are talking about. I found compatible ram on crucial, and ordered 2 1 gig sticks, and they work fine. Considering that EFI isn't hacked yet, I kinda want to just buy a new CPU, and ebay my old one. So I want to know what's compatible, and what isn't.Peace,- RobAlso, would I be able to add a quadcore C2D to my iMac? That would be hella sweet. Thanks!

[uuu_uuu]

Thanks for the tip!

 

I tried you SPD change on my early 2006 20 inch iMAC (2x1GB stock Apple Ram 'micron' type cf Cpu-z). I.e. the same parameters for the 333 FSB setting as you posted (I chose 3,4 rather than 3,4,5 as possible CAS timings, loosing the parameters for 166 Mhz FSB, which shouldn't be an issue).

 

A 'windows Restart' caused the imac to stall (black screen, blinking light on the front of the imac, as with a firmware upgrade, et cetera) , but after properly shutting down the machine and pulling the power cord, the iMac started with no problems .

 

I have only run the machine for a day or so, but so far there have not been any problems... I didn't run any stress tests or benchmarks but 'safari seems snappier' :-).

[PJALM©]

The iMac uses the socket 479 Mobile Core 2 Duo so any Mobile Core 2 should work fine. There is a mobile Core 2 Extreme Quad which works fine but is quite expensive. I would sugest checking eBay as mobile processors are a bit hard to find in stores.

[AlexeySob]

The iMac uses the socket 479 Mobile Core 2 Duo so any Mobile Core 2 should work fine. There is a mobile Core 2 Extreme Quad which works fine but is quite expensive. I would sugest checking eBay as mobile processors are a bit hard to find in stores.

Mobile Core 2 Extreme Quad? :mellow: I don't think there is such CPU.

 

BTW, how do you think, can I install new mobile Penryn CPU into the white iMac 20'' 2 GHz? Will I have problems with compability or overheat?