View Full Version : IDE Positioning

16-12-2002, 03:02 PM
Hi folks,

Now, I know we've had this one before but with some variation. I'm looking for a definitive answer:

I've got a DVD-ROM in the PC I made and 2 HDD's, 1 11Gig with System files and games on it, and a second 7 Gig HDD with MP3's and Music vids on it.

Ideally, I want faster access to the ROM drive and the 11 Gig HDD, it doesnt matter as much about the Media drive.

Where on the IDE Cables, and on which Cables should the drives be placed, and also why?

Thanks in advance


16-12-2002, 03:03 PM
Oh, BTW, I enabled S.M.A.R.T. so thanks for info about that, but what is DMA and why might I need it? Should I have it enabled?

Graham L
16-12-2002, 03:25 PM
DMA is Direct Memory Access. IDE has traditionally used PIO ProgrammedI/O, and it is still the default.

PIO is a conversation between the device and the CPU. CPU: "Give me data", Device: "here it is", CPU: "give me data", Device: "here it is". The CPU waits for the device (or for an interrupt) for the device to return.

In DMA, the CPU sets up a transfer, by loading registers, and the device handles it without direct control by the CPU. It can be faster. Floppies have always used DMA ... I suspect it is because the early PC CPUs were so slow that they had trouble handling the data rate from floppies. Hard disks had more expensive (complex -- "intelligent") interfaces, and were not such a load on the CPU.

If a drive can do DMA, it's probably best to enable it. I'm not sure, but you may find that DMA is enabled or not for both drives on an IDE channel.

16-12-2002, 08:28 PM
rule of thumb..keep cd drives seperate from harddrives. eg hardrives on primary ide and the cd on secondary ide.

dma should be enabled where ever possible otherwise you will get a big slow down. just note- there sometimes is a bug where the dma shows as disabled when in fact it is enabled.

16-12-2002, 09:12 PM
Chilling_Silence I would place the 11GB on the primary IDE and have the second HD and CD-ROM on the secondary IDE.

Having the CD-ROM on the same IDE as the 11GB will bring the speed down to the lowest common speed (Ie DMA 33 - the most likely speed of the CD-ROM).


16-12-2002, 09:30 PM
i think he has DVD drive which is usually ata66 ;-)

provided the drive you are reading from(DVD) is on a different ide to the one being written to (main HD) it won't matter much which way its hooked up.