Hier ga ik toch eens iemand quoten van [url=http://www.cubeowner.com/forums//index.php?showtopic=7843]deze [/url]draad :
echnically speaking all DRAM devices built to safely run at 133MHz, should also run at 100MHz too. However, not all PC133 DRAM devices are also tested by the manufacturer at 100MHz frequencies, as most Chipsets and motherboards on the market today, run at a minimum frequency of 133MHz.
The important thing is that the DRAM devices are capable of a refresh rate of 7.5 ns (ns = nanoseconds) if you have upgraded the CPU in your Cube, OR, if you have not yet done so, that the refresh rate can “slow” down at 8 ns.
Also, the programmable burst length must be minimum of 4-bits, better if it can go to 8-bits or up to a full page length.
See Apple Developers Notes - RAM Electrical Specifications for the Cube, for more details.
Furthermore, especially if you are mixing SDRAM modules inside your Cube, you should be aware that:
The key component inside your Mac which determines how to correctly address the RAM banks, is a chip soldered on your logicboard called “Memory Controller” (in the PeeCee world, such chip is also known as “Northbridge Chipset”); every computer has one.
The Memory Controller fitted inside your Sawtooth is called by Apple engneers “Uni-North Bridge and IC controller” (the "IC"bit stands for Interrupt Circuits). You can read more about such fella’ in this link if you are curious.
Such chip is responsible for addressing all your SDRAM modules by reading, writing data on them and by transferring such data back & forth along the Memory Bus and Processor Bus. These “buses” are in fact inprinted electronic circuits on your logic board, connecting the CPU to the Memory Controller and the latter to the RAM banks. Such buses are set to clock at 100MHz frequency on your machine and have a bandwidth of 64-bit; that means that in any given second, data can travel along such buses up to 800MB in capacity.
The Memory Controller “sees” the SDRAM modules as a single “large” RAM data “pool” (availability); it does NOT recognise your SDRAM modules as single entities.
Every time you boot your Mac up, one of the booting sequences performed by the system is for the Memory Controller to check what are the minimum data specifications held in the FIRST RAM slot available on the logic board. The RAM slots are those “rails” in which you fit the SDRAM modules into. Your first RAM “rail” is labelled "Jnn (where “nn” could be a number like “19” or “20”). SDRAM modules have soldered on them a very small chip, called “SDP EEPROM” (= Serial Presence Dedect EEPROM), which stores on it all the main specification parameters of the (S)DRAM devices, such as: maximum frequency the devices can run at (e.g. PC100 or PC133), CAS latency (e.g. 2 or 3), maximum voltage absorbed (usually 3.3 volts), minimum refresh sequence timing (e.g. 8ns or 7.5ns - ns = nanoseconds), etc.
Once the Memory Controller has “read” such parameters from the SPD EEPROM chip on the FIRST module, it will configure it’s TIMING parameters to address the RAM “pool”; in other words, it will use such parameters for ALL the other modules aswell.
Thus, if in your first RAM expansion “rail” you fit a SDRAM module with, say, a CAS latency value of 2 at 100MHz frequency and on your second or third RAM expansion “rail” you have fitted anoher module bearing a DIFFERENT and LESSER specification, say CAS latency of 3 at 100MHz, THEN such module will be unable to return it’s data readings IN TIME to the Memory Controller; this will very likley generate an unstable data rate between the Memory Controller and the RAM banks.
Since OSX is a very demanding operating system about RAM data availability, the above instability will ALSO reflect on “funny” behaviour of your whole system.
It is best, then, to fit into the FIRST RAM expansion rail your WORST in specification SDRAM module, so that your Memory Controller will adapt it’s TIMING PARAMETERS to such “worst case”. The other modules, bearing better specifications, will handle such TIMING effortlessly.
I know the above sounds a bit too technical, but I hope you will understand just the same.
In my humble experience, I have found that buying my SDRAM modules from reputable online vendors, such as Crucial Technology and/or MacGurus have proven to be worth while the extra money paid for them. Besides, I have also found their after sales service extremely helpful and thorough.
Based on my above experience, I would strongly reccomend them both.
This so as to be complete.
All the best.
Dus alle krediet naar Costa voor bovenstaande uitleg.
Nu is het wel zo dat bij jouw alle modules verschillend aangeduid staan in systeemprofiel, dat is dus anders dan wat costa zegt. Misschien helpt het je wel echter een beetje verder.