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Hard Drives Sharing Cable

T

TheCorm

Diamond Member
Hello,

When you have two hard drives sharing one IDE connected on a double cable, if one is UDMA66 and one is UDMA33 and the board supports up to UDMA66, they would both only run at UDMA33, right??

But, if you have a 5,400RPM drive and a 7,200RPM drive (both UDMA66) they would both still spin at those speeds though yeah since it's an internal thing rather than an interface.

Also, I know there are UDMA100 cables but is there a difference between a cable for UDMA33 and UDMA66?, my local retailer just sells them as IDE cables.
 
When you have two hard drives sharing one IDE connected on a double cable, if one is UDMA66 and one is UDMA33 and the board supports up to UDMA66, they would both only run at UDMA33, right??

yes, that is part of the spec, the channel runs at the slowest\oldest specification present.

But, if you have a 5,400RPM drive and a 7,200RPM drive (both UDMA66) they would both still spin at those speeds though yeah since it's an internal thing rather than an interface.

correct. the controller could care less how fast each spin. rpm has nothing to do with DMA specifications.

Also, I know there are UDMA100 cables but is there a difference between a cable for UDMA33 and UDMA66?, my local retailer just sells them as IDE cables.

ata33 cables are 40 wire ribbon cables with 40 pin connectors, 40/40 cables.

ata66 = ata100 cables are 80 wire ribbon cables with 40 pin connectors, 40/80 cables.

if you look at the cables themselves, you can tell that the 40/80 cables are finer with respect to the wires... needless to say the ata66 cables are more expensive.
 
Not correct. Most modern chipsets support 'Independant Device Timing', each device runs at its own speed.
 
Is that so? that would explain the lack of increase in HD cache performance when i moved my dma33 cdrom to another channel. do you have something to back this up?
 


<< yes, that is part of the spec, the channel runs at the slowest\oldest specification present. >>

I'm also going to have to challenge this statement.
 
I'm gonna have to fully side with Mday on this one, I had a feeling about the spin speeds, sounds all in order.

Corm
 
If you want info on Independant Device Timing, try Storagereview.com. Independant Device timing has been around for a while, most new chipsets have the capability. I wouldn't mix PIO mode devices with (U)DMA devices.
 
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