High vs Low density RAM? (X30)

[RageRover]

Is there an advantage or disadvantage when it comes to the density?

What about system performance?

or does it really not matter in the end and what matters is the total amount of RAM/memory installed?

Can you use one low density and one high density module in the same system? would they have to be the same size modules (i.e. both 512mb, but one is low and the other high density)?

Thanks

[rkawakami]

Assuming for the moment that the chipset can handle both low and high density modules, then the only advantage would be for using the high density version. The reason? Generally the higher density module will have an overall lower power consumption.

Performance will be the same regardless of the density. The system will only operate at 133Mhz timing (we're talking about the X30 here). Also, I don't believe that it will run any faster if you use CL2 (CAS latency 2) modules vs. the standard CL3. This is a function of the system chipset, which I believe is locked into the CL3 timing. You can put faster spec'ed memory modules in the system, it will still run at PC133.

And getting to your last question, again, assuming that the chipset can handle both densities, you should be able to safely mix and match them. You also do not have to install them as a matched size set.

edit: Just realized I didn't make this clear earlier... As far as using low density modules in a system which can handle high density: there is a slight disadvantage to doing this. There will probably be a slight increase in the power consumption because of the amount of "refresh" cycles that the modules are getting. The main difference between low and high density memory is the amount of refresh cycles you need to give them in order to maintain the data. The high density modules require twice as much as the lower density modules. But becaue they are designed this way, the overall power draw is about the same as the low density modules, given that they are operated to spec. Because the lower density modules require half as much refresh cycles, imposing double the amount (a function of the system chipset) means that the data is refreshed twice as often (a good thing since you don't want to lose any), but, the lower density module will also consume more power doing so. We're not talking much, maybe a couple of minutes out of the 3 or so hours that you can operate off a battery.

[RageRover]

Thanks for the info, I greatly appreciate it.

So basically, other than loosing a few mins of battery life, there is really no disadvantage nor advantage to using low density?

As far as the refresh rate being higher with low density, wouldnt that technically mean the system would be slightly faster with low density? Or maybe just on paper it would be faster?

Anyway...I am currently using a low density 512 module. I purchased a new battery 2 months ago, and I use NHC. I can sqeeze about 6hrs of life from the battery. Although I usually have the LCD at its lowest setting to obtain that number.

If the ram is drawing additional energy, I dont notice it. Like you said, I probably only loose a couple of mins of battery.

Thanks again for the info.

[rkawakami]

So basically, other than loosing a few mins of battery life, there is really no disadvantage nor advantage to using low density?

That would be my opinion, yes.

As far as the refresh rate being higher with low density, wouldnt that technically mean the system would be slightly faster with low density?

I don't believe it will make any measurable difference in speed. Here's why: the chipset will probably use a method of refreshing the memory modules which is called "hidden refresh". Basically it's a single clock cycle that will occur at a time when nothing else is going on. As long as it generates 8192 of those clock cycles every 64mS (milliseconds), a high density module will be operating within spec. The low density modules only require 4096 of these refresh cycles in the same amount of time. If they "see" 8192, then all that means is that they are completely refreshed twice, ergo, no problem with operating properly. As long as the chipset is locked into generating 8192 refresh cycles, then there will be no difference between the two densities. Now, assuming that the chipset is "smart" enough to read the SPD information off of the module and decide that only 4096 refresh cycles are needed when low density modules have been installed, then all you are really saving is 4096 "extra" cycles of 7.5nS (nanoseconds; this is the 133Mhz clock rate), or somewhere around 31uS (microseconds), every 64mS. That works out to be a reduction in the number of total clock cycles of 0.05%. That's how much faster your system would run .