Why do (all?) DVD-writer only have "UltraDMA 33" where some DVD players have ATA/100?!

[Dance123]

Hi,

How come that as far as I can see most (all?) DVD-writer use only UltraDMA33. Isn't that old technology, if you know that most devices are ATA100 and faster? Even DVD-writer use ATA/100, so why do DVD-writer only have 33?!

 

[13black]

Probably has to do with the speed, X16, X24 etc. From what I see a DVD writer can also read but only at a slow speed. Probably not fast enough to need ata 100 speed. A DVD reader, CD-rom reader can read at much higher speeds so it needs the ATA-100 speed to do it. Burners are getting faster all the time so I would say enventually they will use ATA-100 too.

 

[Algere]

It'll probably shift to the SATA interface before it can take advantage of ATA 100.

 

[zodder]

Plextor is very close to revealing their SATA 12x burner.

 

[Peter]

It's irrelevant - IDE drives do not share bandwidth, and the ~27 MB/s achieveable with UDMA mode 2 ("UDMA33") is plenty enough for anything CD or DVD. That's about 180x CD speed and about 20x DVD.

 

[VirtualLarry]

Originally posted by: Peter
It's irrelevant - IDE drives do not share bandwidth, and the ~27 MB/s achieveable with UDMA mode 2 ("UDMA33") is plenty enough for anything CD or DVD. That's about 180x CD speed and about 20x DVD.

I'm kind of curious why you say that they don't share bandwidth - since if two IDE devices are on a channel, they most certainly do. If ATA-33 is only fast enough for a 20x-speed DVD reader or writer, then that means, in order to properly support 16x DVD disc-to-disc copying between two devices on the same IDE channel, then they will eventially have to move to an ATA-66 or ATA-100 interface. I agree though, that they will probably move to SATA before that ever happens.

I'm actually a bit curious about this myself, but I'm guessing that implementing an ATA-100 interface properly, requires a bit more engineering work, and components with tighter specifications (meaning higher component costs).

It's not widely known, but ATA-100, properly implemented, runs on a lower signaling voltage (3v, I think) than alll slower ATA speeds (default is 5v). I've actually somewhat wondered about how that works in terms of compatibility, with putting an ATA-33 optical device, slaved to an ATA-100 HD, on an IDE channel connected to an ATA-100 controller. I know that it generally works, so there must be some voltage conversion, or at least tolerance, going on there.

I really miss SCSI...

 

[Steve]

They don't share bandwidth. When one drive is using the channel, the other has to wait its turn, until the first drive is done.

 

[Peter]

Exactly. IDE's Master/Slave setup means there is only one drive controller on the cable (in the Master), which can only work on one command at any given time. Thus, the idle time between command issue and data transfer cannot be used by the other drive. (SCSI, having one controller in each drive, can pull that trick.)

So if you put two 60 MB/s hard disks onto an UDMA-133 channel, you get 60 MB/s aggregate throughput not the 120 you'd expect.

 

[jjlawren]

Originally posted by: Peter
Exactly. IDE's Master/Slave setup means there is only one drive controller on the cable (in the Master), which can only work on one command at any given time. Thus, the idle time between command issue and data transfer cannot be used by the other drive. (SCSI, having one controller in each drive, can pull that trick.)

So if you put two 60 MB/s hard disks onto an UDMA-133 channel, you get 60 MB/s aggregate throughput not the 120 you'd expect.

A lot less than that if you're transfering between drives.

 

[Peter]

I wasn't accounting for command, seek, rotational latency and master/slave drive switching overhead. Real life is even worse, that's correct.