Understanding 8MB buffer?

Richard Dower

My question is in relation to the Plextor 712A/SA drive. The buffer size is 8MB, but does this buffer act in BOTH directions?...as in is it a read and write buffer?

Or is it a write only buffer?, as in data coming into the drive?, i've got a Asus E616A DVD-ROM and it has a 2MB buffer, and i'm assuming that's a read buffer. Can anyone help me understand further please?

Arrow

I don't think that all the 8 MBs are used when reading discs. Usually all the read onlz drives have some buffer like 512k or so. But any better information would be interesting.

hwp

Not all buffer memory is available. Look at the supported drives list of Feurio (Burning Software specialised on Audio): http://www.feurio.com/index_german.shtml

You can see that for example a PX-708 while having 2MB total buffer only 1162KB actually are free for use. Similarly the PX-716 has 8MB total buffer of which only 4690KB are available. As for how much of it is used for read buffering i've never seen any information. But i have no doubt read buffering is done. ODDs with slow access times are a prime candidate for chaching read data. Of course such caching is nowadays done much chaper by the OS in the available RAM of your computer...

greg42

This is a write buffer.

Why would you need a read buffer ? Your PC's OS already has a read buffer

That is memory used inside your writer to store pending data to be written, ahead of time..... To help compensate for slowdowns or other system tasks....

Example:

When initiating a write operation, the software will first cache 8MB of data to be written inside that internal memory....then the drive will start writing to disc, feeding off the RAM little by little, all while the buffer keeps getting filled. This is to avoid any buffer underruns, causing the laser to stop. That buffer is NOT used for reading.

seeker010

to mess up eac of course. if you could make a copy of a disc without pops and dicks what excuse would you have to buy another copy.

DrageMester

The Plextor PX-712 caches audio data according to EAC. Whether that is cached in the 8MB buffer or in another buffer is unknown to me.

So there is at least some read caching going on in Plextor drives!

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bob11879

most audio playback is at 1x throughput to the PC. Since most drives do not play down to 1x, there is some caching in the drive to match the lowest drive speed (4x or so) to the 1x output for audio.

DrageMester

EAC and other programs don't rip at 1x, they rip at the drive's maximum speed e.g. 40x, or whichever speed you select, so I don't see how your argument applies here?

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G@M3FR3@K

Playing and ripping audio are two different things DrageMester

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DrageMester

This was the very point I tried to make in my post. Was it so unclear that you have to point out to me, what the point of my post was?!??!?

Since playing audio at 1x and ripping audio at 40x (or whatever) in EAC are two different things, I just don't understand the point of bob11879's argument.

In any case, since EAC reports that the Plextor PX-712 is caching audio data when audio is being ripped (not played at 1x) from the disc, then there must be some buffer in the drive capable of caching the audio data. Whether that buffer is part of the 8 MB is not known to me, but I also don't think that it really matters, since there obviously is some form of read buffer in the drive!

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