UMDA Codes? (1 Viewer)

[Dan M~]

Can someone explain or direct me to an explanation of UMDA codes for hard/CD/Zip drives? If I mix a UMDA2 drive with a UMDA6 drive, do I limit all drives to UMDA2? Does it work that way? Help.. I'm ignorent!

 

[Ken Chan]

Really in-depth stuff reprinted at storagereview.com. It doesn't mention UDMA6, but I guess that's the 133MB/s flavor, which of course no drive is even close to sustaining.
Short answer is that the slower one does not limit the faster one, if the controller supports independent master/slave device timing, which most modern chipsets/controllers do.
//Ken

 

[Dan M~]

Thanks Ken!

I just put together a new PC after my last one was torched by lightning. On the Primary IDE channel I have a new WD hard drive, 80 GB (Ultra ATA/133, 7200 RPM,133 MB/s Data Transfer Rate}, that shows up as UMDA6 in the bios. On the secondary IDE channel I have a Phillips 2400 CD-R/RW drive and an internal Iomega Zip 250 drive. Both show as UMDA2 in the bios. I would expect the CD drive to be "faster" then UMDA2 (but what do I know). I was afraid that the zip drive was slowing down the CD drive. Any comments?

 

[Ken Chan]

Well, 1x CD-ROM is 150KB/s. So a 40x CD is a piddlin' 6MB/s. The Zip is probably less that that, but both are well under the 33MB/s of UDMA2/ATA33, so it doesn't matter. In other words, the drives' limiting factor is their own respective read/write speed off their disks, not the interface, which is plenty fast enough.
It's worth repeating that your hard drive's 133MB/s data transfer rate is the rate from the drive buffer. With say a 4MB buffer, that means it will flush in 0.03 seconds, and then it will have to read off the disk. Modern drives can do 40 to 60MB/s (the sustained data transfer rate), which of course isn't bad, but it's not even half of the advertised rate. So for example, if you wanted to read a 133MB file into memory, you might think it would take one second. But what happens is that -- if the first part of the file is in the buffer, a big if -- the first 4MB will fly out in 0.03 seconds, and then the other 129MB will take two, three, four, or more seconds to read.
Anyway, your setup sounds fine, unless for some bizarre reason, you want to burn files directly from the Zip onto the CD. In that case, two devices (the master and slave) cannot use an IDE channel at the same time, so that would be slower. Whether that's slow enough to create coasters is another issue, and also depends on whether the burner has some buffer underrun protection, like BURN-proof or "Seamless Link".
//Ken

 

[Dan M~]

Thanks again Ken,
I feel better about what I am seeing in my bios.
Looks like I made the correct decision to group the zip (only used for some legacy files I have on zip disks)and CD drive (used to back-up the HD and burn music and video CD's).
Thanks again for the help.