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John,

Sorry if this sounds stupid, but are we saying the when we play music from our HD it is first is dumped into our RAM and then streamed out to our hardware? Is this what is happening if we listen to a net music stream that is sent to our RAM first and then sent to our outboard hardware?

Yes.

Data that your computer reads is stored in various places. To oversimplify it a bit, the more often or more likely it is that a particular piece of data will be needed by the CPU, the "closer" it keeps that data to itself. With that in mind, there are three main places that data is kept. From furthest from the CPU to closest to the CPU, there is data on your hard drive, data in the RAM, and there is data in the CPU's cache. It also happens that the further data is from the CPU, the longer it takes to access.

Think of it like when you are working with various screwdrivers in your tool box. If you have to keep using a particular screwdriver often, you keep it close to you, and for other rarely accessed things, you go into the toolbox and find it.

Anyway, to answer your question finally....YES! When the CPU needs to read a file, it usually brings it in from the HD to the RAM. The particular bits that are going through the CPU are also brought in from the RAM to the CPU's cache. Computers also store temporary files on the HD. So using some sort of algorithm, data is kept in all three places: cache, RAM, and the HD. Even though the data is being sent out to the bus and eventually through USB, it still goes through the CPU as far as I know.

Bottom line: Usually the CPU will look for the data it needs in the RAM and if it's not there, it has to go find it on the hard drive's page file (like RAM but on the HD), or if it's a file, from the file directory.

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It is starting to appear that the more your computer accesses the hard drive, the less good the sound, though on an unpredictable basis. Perhaps this is power supply-related, as substituting a solid-state drive for my TiBook's hard drive made any RAM-related difference disappear.

John Atkinson
Editor, Stereophile

Thanks for your reply John.

I find that somewhat strange, despite alluding to it in my original post. I must admit that it has been many years since I studied the operation of computers, so I may be off base here, so bear with me. My suspicion is that you won't see incremental increases in sound quality by adding RAM, as WP suggests, unless you are playing huge uncompressed files.

1. A computer keeps files that it has accessed recently in RAM.
2. Because RAM space is finite, a computer keeps additional files that it need to access frequently in a page file, which is located on the HD.
3. If data it is looking for is not in RAM, it looks for it on the hard drive.
4. Unless you turn page filing off, having more RAM merely makes trips to the hard drive's page file less frequent.

So if the music file you are playing is in RAM, you don't need to access the hard drive, and according to you, there is less electrical noise which causes a loss in audio quality.

But if the music file has not been accessed recently, no matter how big your RAM, the computer still has to read from the HD, thus causing sound quality problems as you describe. AFAIK, the computer is always going to read from the HD unless 1) the music playing program is able to buffer the entire music file in RAM or 2) the entire music file is still in RAM from a previous accessing of that file.

These "unless" conditions are pretty easy to meet for your average lossless compressed file, but admittedly, it may be a problem if you are trying to play uncompressed WAV files with high sample rates. For example, for a large file, the computer may choose to only buffer part of it in the RAM and then move pieces in and out as the song's progress continues.

Anyway, I am more interested in this on an intellectual level than any practical reason, as I use a networked music player, but I wouldn't guess that Wes will see increasing gains in sound quality as he goes up in RAM so long as the entire song is in the RAM. And for that to happen, there's probably no reason to max out the RAM. You just need a healthy amount.

In the time it would take to understand all of this, you could install more RAM and be done.

Thanks Orb. What is going on is indeed pretty complex and that is why I am skeptical that maxing out RAM to 6GB would help.