ATA/100 IDE Bus Speed Question

[nulldev]

Hey all. I hope I'm putting this in the right forum.

I recently put together a new machine and now have the ability to do ATA/100. I only have one device (hard disk) capable of doing ATA/100, whereas the others say they are Ultra DMA 33 or ATAPI(and they quote no speed).

I've done a TON of searching for information on mixing devices with different speeds on an IDE channel. Some sites say the ENTIRE channel slows to the speed of the slowest device. Other sites claim the speed of the slowest device only comes into play when you are transfering data between the two devices on the same IDE channel.

I'm looking to put the hard disk and a Kenwood CDROM(72X) on the same IDE channel. The Kenwood is rated at Ultra DMA 33 and the IBM hard disk at ATA/100. If the hard disk is putting data to memory, will it store it at 33 or 100?

Hopefully this all makes sense.

Thanks again!


PS: I understand that the 33 and 100 are burst speeds and not constant like SCSI. Has anyone seen a big improvement from 33 to 66 to 100?

 

[Radboy]

This is my understanding, but I'm not 100% sure:

You can run any combo of ATA33/66/100 on same channel, all at max-rated speeds, but can have probs with DMA + non-DMA devices on same channel.

Again, not positive.

 

[xtreme2k]

why not run some benchmark to test it

get HDTach and look at the burst rate of your HDD when it is by itself, and then with the CDROM

 

[nulldev]

Ok, thanks for the info!

I'll also go try to find a copy of HDTach and do some benchmarking.

 

[DaddyG]

If the devices that you are mixing support DMA, either DMA or UDMA then you should see no performance loss. If any device is PIO then the controller will run all devices PIO mode.

 

[RSI]

"Ok, thanks for the info!

I'll also go try to find a copy of HDTach and do some benchmarking."

Head on to TCDLabs to get your copy of HD Tach.

If you have an ATA/100 hard drive, ATA/100 compatible cables and an ATA/100 controller or ATA/100 compatible motherboard, then you are all set. If you have other hard drives using older transfer modes such as ATA/66 or ATA/33 (you can call it Ultra DMA/66 or whatever you want), they will simply run at that speed.

If you're copying a file from HD 1 to HD 2, obviously it will only be as fast as HD 2, since HD 2 can't transfer as fast as HD 1 (assuming HD 1 is ATA/100 and HD 2 is ATA/66 or 33).

Hope I've helped some, and didn't confuse you. :Q

-RSI