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PATA config - One optical one HD??

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September 13, 2006 12:40:41 PM

Hello,

I am building a new rig here shortly. The mobo I am going to get has one PATA port and I want to reuse my DVD burner and a 120gb hard disk (Data only). I am going to get a SATA DVD rom and SATA harddisk for the OS.

Can you put an optical drive and a hard disk on the same PATA channel. I understand the whole master/slave/cable select thing, but I have just always kept optical on one PATA channel and HD on the other. This is the first build with only one PATA channel.

More about : pata config optical

September 13, 2006 1:07:09 PM

yes, why not?
September 13, 2006 1:14:21 PM

Yes you can, but the hard disk will be slowed to the DVD±RW's speed, which is sslloowww transfer.
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September 13, 2006 1:27:57 PM

I don't mind if it is slow, but would there be an advantage to making the HD master and the optical drive the slave in cable select mode?

This is basically for storing MPS's, pics, video, drivers, etc.
September 13, 2006 2:18:58 PM

uh... i've just tested this, put an ata100 disk on the same cable that a cd-rom and the disk was working at ata100
i've seen people saying the same thing about disks working a cd-rom speeds when connected to the same cable.. where did this statement come from?
September 13, 2006 2:25:03 PM

Quote:
I don't mind if it is slow, but would there be an advantage to making the HD master and the optical drive the slave in cable select mode?


It's better that you put those peripherals in their dedicated mode. HDD is Master and Optical drive in Slave. Choosing Cable Select mode will make transfer rate more slower in case your HDD and optical drive work in the same time and less conflicted.

I hope your DVD writer has a burnproof technology and management or similar like that. If someday you want to burn your stored videos, mpS, pics, you'll see that memory buffering while burning will go up and down and time to burn will take more longer.
September 13, 2006 3:06:20 PM

1.Set hd as Master, optical drv as Slave with 80-pin pata cable

2.If transfering data from sata to pata hd, write speed to pata drv would be 133 Mbps max (theoretically and if supported by both hard disk and controller)

3.write speed (copying data) from optical drive to pata disk would be reduced from theoretical max speed due to the use of same cable
September 15, 2006 9:30:13 AM

Its simple really - if they are on the same cable they will both work at the slowest interface speed, so for example if your disk is ATA133 and the CD is ATA100, they both will run at ATA100, but this should be fine.
September 15, 2006 11:23:23 AM

Quote:
Its simple really - if they are on the same cable they will both work at the slowest interface speed, so for example if your disk is ATA133 and the CD is ATA100, they both will run at ATA100, but this should be fine.

i would like to know where did this information come from.
by the way, the fastest optical drive i've seen until now was ata33, even modern dvd burners
September 15, 2006 1:24:37 PM

Quote:
Its simple really - if they are on the same cable they will both work at the slowest interface speed, so for example if your disk is ATA133 and the CD is ATA100, they both will run at ATA100, but this should be fine.

i would like to know where did this information come from.
by the way, the fastest optical drive i've seen until now was ata33, even modern dvd burners

See below... My experience comes from where I used to work for a computer manufacturer at around 1995 to 1996, I suppose things have changed a little....

Mixed device speeds
It is a common misconception that, if two devices of different speed capabilities are on the same cable, both will necessarily transfer data at the speed of the slower device. This is true only with very old chipsets or add-in adapters. All modern ATA interfaces (since, at least, the late Pentium III and AMD K7 era) support independent timing, which allows each device on the cable to transfer data at its own best speed.

However, due to the omission of both overlapped and queued feature sets from most real-world parallel ATA products, the preceding paragraph must be clarified. It applies to the data transfer phase, but this is usually the shortest part of a complete read or write operation. Devices do differ markedly in the total time required to perform an I/O (irrespective of the burst data transfer rate), and since only one device on a cable can have an operation in progress at one time, they do affect each others' performance.

For example, consider an optical device such as a DVD-ROM, and a hard drive on the same parallel ATA cable. With average seek and rotation speeds for such devices, a read operation to the DVD-ROM will take an average of around 100 milliseconds, while a typical fast parallel ATA hard drive can complete a read or write in less than 10 milliseconds.

This means that the hard drive, if unencumbered, could perform more than 100 operations per second (and far more than that if only short head movements are involved). But since the devices are on the same cable, once a "read" command is given to the DVD-ROM, the hard drive will be inaccessible (and idle) for as long as it takes the DVD-ROM to complete its read—seek time included. Frequent accesses to the DVD-ROM will therefore vastly reduce the maximum throughput available from the hard drive. If the DVD-ROM is kept busy with average-duration requests, and if the host operating system driver sends commands to the two drives in a strict "round robin" fashion, then the hard drive will be limited to about 10 operations per second while the DVD-ROM is in use... even though the burst data transfers to and from the hard drive still happen at the hard drive's usual speed.

The impact of this on a system's performance depends on application. For example, when copying data from an optical drive to a hard drive (such as during software installation), this effect probably doesn't matter: Such jobs are necessarily limited by the speed of the optical drive no matter where it is. But if the hard drive in question is also expected to provide good throughput for other tasks at the same time, it probably should not be on the same cable as the optical drive.

On the other hand, it is worth emphasizing that this effect only occurs if the slow drive is actually being accessed. If it is idle, its mere presence on the cable will not affect the performance of any other device on the same cable (provided, of course, that the host adapter supports independent timing).
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