Maximum safe voltage on this ram chip?

[Geeky1]

So I'm playing around with an old G4 (yes, I know... boo, hiss, etc. etc. ) and I'm trying to overclock it.

Now, overclocking a 6 year old Mac is a little bit different than overclocking a modern PC; it involves resoldering little surface mount resistors on the CPU module. Call me masochistic if you must, but I like this more than I like overclocking PCs. It's more of a challenge.

Anyhow. The CPU module in question has two 533MHz PowerPC 7410 (G4) processors on it, and they have external L2 cache. The cache chips run at half the processor clockspeed (so 267MHz in this case). The chips are Samsung branded, model K7A403609A-QC27.

Here's the question:
I found a datasheet for-I think-these chips, here:
http://www.ortodoxism.ro/datasheets/SamsungElectronic/mXvvsrw.pdf

Looking at page 2, it says that the VDD and VDDQ specs on this thing are 3.3v; I know that they're run at 2.5v in the Mac. My understanding from what I'm reading is that I should be able to dump 3.3v into these things with no problem at all. Am I reading the spec sheet correctly, or am I going to crater one of these cache modules?

Thanks.

 

[BillParrish]

Boom ! ( I think) You do NOT want to mess with Vddq !!!
(Well maybe it will just not work as the cpu and main memory are expecting/driving 2.5V nominal on the data and address buss. Not sure what would exactly happen but it would not be a good thing. )

Are you SURE the chips Vdd is 2.5V ?

Looking at page 7 typical Vdd is always 3.3V for both possible I/O pin voltages.

There are two possibilities of I/O voltage.
3.3V I/O (Vddq)
2.5V I/O (Vddq)

Those are the address and data lines and you do NOT want their nominal voltage to change.

If you are absolutely certain that Vdd is 2.5V (and that is not per spec sheet and makes me wonder as it is below the min Vdd for the chip on the spec sheet. Way out of spec and makes no sense).

VDD= 3.3V+0.3V/-0.165V Power Supply.
VDDQ Supply Voltage 3.3V+0.3V/-0.165V for 3.3V I/O or 2.5V+0.4V/-0.125V for 2.5V I/O.

Per the spec sheet you pointed to, it appears that Vdd should be 3.3V nominal and that is all I am going to say.

 

[Geeky1]

Now you've got me wondering. I don't know what the actual voltage is, no. There's very little information out there on this stuff, and I'm going by what I've read, not an actual voltage reading.

I suppose i'll have to measure it somehow (gonna be fun, considering the location of the cache chips relative to everything else on the board... )

 

[JumpinJack]

I have overclocked the single CPU version of the 533 G4 dozens of times, but I had no luck with the Dual 533 G4 version.

Obviously you know how to set the multiplier jumpers. If not see;
http://xlr8yourmac.com/systems/Dual_533_overclock/dual_g4_533_overclocking.html

To boost the Voltage to the RAM cache, replace the R51 resistor with a 100 Ohm resistor. See;
http://www.xlr8yourmac.com/systems/DA_CPU_in_Sawtooth/DA_CPU_mods.html

The G4 7410 CPU cores are set at 1.7 V supply, with a maximum rating of 1.8 V. I have not had much luck getting the CPUs to go faster by giving them extra voltage. Although it did start-up at the Dual 600 MHz setting, it froze after 5 minutes of use, even with 2.9 V to the RAM cache.

The resistors for CPU voltage are listed under section 2 on the following page;
http://www.xlr8yourmac.com/G4ZONE/sawtooth/SawtoothCPUdesign.html

Happy New Year!