Why is it that it is 'recommended' by Dell and others that when installing memory sticks that they should be 'matching' to work ? My current configuration shows both the 128 and 256 installed and recognized and working properly. I have two slots.

It is a Dell Dimension XPS B1000r Special Edition. (also, what is the best way to check compatibility w/o trying to deal w/ dell help center?)

Am I offbase here ? Thanks, M

Matching memory is More directed toward memory speed than amount on the dimm

I get all my memory from
http://www.crucial.com/

I have never had a problem with ANY memory purchased from them

Matched memory setups are as per the motherboards capability usually DDR [not always] RAM, regular SDRAM as in your situation can be mixed and matched without any speed loss.You might find [if your going to upgrade] buying "OLD" SDRAM Ram can be more expensive then you might think.
Dell, is the last place you want to buy anything, #1--They has people that dont know what they are talking about 80% of the time.
#2-- You WILL pay more then you really should.
#4-- Get your Dell specs out and make sure you can upgrade beyond where your at now, you might have to FLASH your BIOS to increase you MAX Memory.

PC 800 RDRAM RIMM........ with NON ECC ? not sure about that but an educated guess.....I'll put them out to examine...I also downloaded the AIDA32 spec program and have it running now. I notice that I'm always running near '80%' of capacity of RAM no matter how many programs I have up or not. Strange ? or no ?

Thanks guys, M

I currently have 1 128 and 1 256..going to get another 256..It looks like the setup will handle 512.

I'm not sure if it's still the same with later Operating Systems [after Win98], but almost all the RAM going spare was put to good use by allocating it as a "Disk Cache".
I used to use "System Monitor" to study the "System Memory" [RAM + swap file etc] being divided up to serve the need of the moment.
If anything has a need for RAM it is taken from the Disk Cache and re-allocated.
All available RAM should be put to good use and there should be little or none going unused.
At this moment, "TClockEx" tells me [down in the System Tray] that my PC has 784 kB of free RAM [unallocated].

Sylvander, that may work well for you, but any tweaking of cahces/swap files should be based on the way a particular machine is used....

In my case my system performs better with a minimal disk cache and a maximum amount of free RAM....because the few microseconds it takes to resize the cache is used by the browser to load the page.

In other words if doing things like playing games, office type apps, video editing etc (disk intensive tasks), then yes a large disk cache is desireable, where as surfing, which is primarily a memory intensive taks benefits from a smaller disk cache.

There is no "one size fits all" when it comes to memory management. That is why so many people seek to tweak the MS default settings....because they are an attempt to be a one size fit. I have even seen some recomendations to setup a couple of different profiles, depending upon what you want to do at the time, optimized to different tasks.

It's nothing to do with me MJC.

My understanding is that Windows does this automatically all on it's own and I have used "System Monitor" to watch it happening.
I was just an observer.
I did no tweaking of the "Disk Cache" [which I understand to be a cache used to improve the transfer of data from disk to disk].
I'll see if I can find any notes on the topic.

HMM!
I just started loking up "Disk Cache" and I get info about the swap file. My recollection was of an area in RAM used for the transfer of data from disk to disk and I thought it was called the Disk Cache.
Perhaps it goes by another name.

OK
I just found some notes on:
QUOTE
VCACHE & CDFS SUPPLEMENTAL CACHE
The memory pool is dynamic and is based on the amount of "Available Free System Memory". i.e. The system allocates/de-allocates memory [for cache] based on system use.
The CDFS driver features 32-bit protected mode caching of CD-ROM data. VCACHE shares the memory pool with the 32-bit VFAT driver. CDFS uses a separate cache which means cache memory can be swapped to hard disk when CD-ROM activity pauses. This gives applications more room to run [in RAM] and reduces the probability of hard disk cache being "flushed out" whenever a large multimedia stream is played back.

My recollection of this is rather hazy, but I do remember that something was automatically being allocated the free RAM so as not to waste it.