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RE: 2 EIDE interfaces. Connecting 2 IDE HD + 1 CDROM.
- To: "'Oded Arbel'" <odeda-linux-il(at-nospam)betalfa.org.il>, shaulka(at-nospam)bezeqint.net, linux-il(at-nospam)linux.org.il
- Subject: RE: 2 EIDE interfaces. Connecting 2 IDE HD + 1 CDROM.
- From: Haggai Sachs <haggai(at-nospam)white-cell.com>
- Date: Wed, 11 Apr 2001 13:55:38 +0200
- Delivered-To: linux.org.il-linux-il@linux.org.il
- Sender: linux-il-bounce(at-nospam)cs.huji.ac.il
You need to consider the exact parameters of your equipment specs -
(ATA33/66/100, 5400/7200 rpm).
Item 1 is correct - IDE/ATA channel can only deal with one request, to one
device, at a time. In contrast, two disks on two different IDE/ATA channels
can process requests simultaneously on most motherboards.
Item 2 is complicated - Optical drives (or other ATAPI devices) should not
be shared on the same channel as a fast hard disk - ATAPI allows the use of
the same physical channels as IDE/ATA, but it is not the same protocol;
ATAPI uses a much more complicated command structure.
Placing 2 mixed HD on the same ribbon won't effect the HD speed (ATA/rpm).
The performance loose will take place when accessing them together, since
the only shared point is "Drive Active / Signal Present (/DASP)" signal
carried on pin #39.
Haggai.
-----Original Message-----
From: Oded Arbel [mailto:odeda-linux-il@betalfa.org.il]
Sent: Wednesday, April 11, 2001 11:00 AM
To: shaulka@bezeqint.net; linux-il@linux.org.il
Subject: Re: 2 EIDE interfaces. Connecting 2 IDE HD + 1 CDROM.
AFAIK,
item 2 is _not_ correct for UDMA interfaces (UDMA33 and above - everyone
does those today), as it multiplexes the calls to the drives, so the faster
drive can get more calls done while the slower one is still processing.
I could be mistaken , though..
Oded
--
One should always be in love. That is the reason one should never marry.
-- Oscar Wilde
----- Original Message -----
From: <shaulka@bezeqint.net>
To: <linux-il@linux.org.il>
Sent: Wednesday, April 11, 2001 09:42
Subject: 2 EIDE interfaces. Connecting 2 IDE HD + 1 CDROM.
> I have the following 2 pieces of data:
>
> 1) An EIDE interface can not handle 2 IDE devices concurrently. Only
> after one of the interfaces has finished doing whatever it was requested
> to the other one can begin its activities.
>
> 2) It is not recommended to have a CDROM and an HD connected to the same
> EIDE interface since the slowest CDROM will make the faster HD slower.
>
> Is this correct?
>
> According to the above, if I have 2 HD and 1 CDROM is it recommended to
have
> each HD on a separate EIDE interface and the CDROM connected as a slave to
> one of them or should I have the 2 HD on the same EIDE interface and the
> CDROM on a separate one?
> --
>
> Shaul Karl <shaulka@bezeqint.net>
>
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