AGP speed 2X,4x,8X: What it really means!

"Chip" wrote in message
...

"J. Clarke" wrote in message
...
Chip wrote:


"J. Clarke" wrote in message
...
PRIVATE1964 wrote:


And that's the only real benefit of SATA that I can see that is
inherent in its being serial--that narrow cable is a lot easier to
route.

Here's a question for you that will keep me from having to search on
related to SATA. I plan on getting a new serial hard drive soon.

I'm using a NF7-S with serial connections.
What is the maximum throughput for a hard drive connected to the
serial
connection.

Is that connection spec'd for 150Mb/sec? I've read that the serial
drives
that are out now are not "true native" serial drives so there is no
way
they could ever hit 150Mb/sec.

What can you tell me about this please.

There is no drive in the world that can fill a 100 MB/sec pipe. WD
Raptors
have a maximum sustained transfer rate of 72 MB/sec, 7K400s max at
62.1,
Cheetah X15s max at 86. The limit is the bits per track and the
rotational
speed, not the interface. So it doesn't matter whether the interface
can
hit 150 or 133 or 100.

... apart from the burst speed which with drives with 16MB cache now
can
be a significant factor, especially with video editing applications
(where
the
caching algorithms have a better chance because of the big files).
16MB
bursting at 150MB/s is not insigificant.

I fail to see how it makes a difference with video editing, where you are
trying to stream several gigabytes of data.

But you are not. You don't load "several gigabytes of data" into memory
and
*then* start processing it. True, the data comes in large chunks - but
not
gigabytes. Its processed piece by piece.


How much real-world difference do you see between a drive with a 16 meg
cache and an otherwise identical drive with a 2 meg cache?

"Some"?


With PATA and two drives per channel, it's possible for both drives
together
to fill a 150 MB/sec channel but SATA allows only one per channel so
that's
not an issue.

In any case, some use a bridge chip, others don't. IIRC Seagate is
not
using a bridge chip. I don't recall what WD is doing, but their
Raptors
outperform any SATA drive from any other manufacturer, although the
Hitachi
7K250 and 7K400 come close, so whether they're using a bridge chip or
not
clearly doesn't make any real-world difference.

The Raptors have a bridge chip too. They are basically SCSI drives
with
an adapter chip on them.

I see. So you are claiming that they have a SCSI interface bridged to
SATA?

Yes. I am not sure to what extent the SCSI interface remains in tact.
But
I know they are not "native" SATA drives, i.e. they are something else
with
a bridge chip. And the "something else" was originally a 37Gb or 74GB
SCSI
drive.

Or are you just saying that being constructed to the same quality
standards
as server-grade drives somehow makes them have a different interface?

Nope. See above.

Chip



Just to add, standard (not the newer raid edition) caviar se sata series are
pata bridged to sata.

Chip wrote:


"J. Clarke" wrote in message
...
Chip wrote:


"J. Clarke" wrote in message
...
PRIVATE1964 wrote:


And that's the only real benefit of SATA that I can see that is
inherent in its being serial--that narrow cable is a lot easier to
route.

Here's a question for you that will keep me from having to search on
related to SATA. I plan on getting a new serial hard drive soon.

I'm using a NF7-S with serial connections.
What is the maximum throughput for a hard drive connected to the
serial
connection.

Is that connection spec'd for 150Mb/sec? I've read that the serial
drives
that are out now are not "true native" serial drives so there is no
way
they could ever hit 150Mb/sec.

What can you tell me about this please.

There is no drive in the world that can fill a 100 MB/sec pipe. WD
Raptors
have a maximum sustained transfer rate of 72 MB/sec, 7K400s max at
62.1,
Cheetah X15s max at 86. The limit is the bits per track and the
rotational
speed, not the interface. So it doesn't matter whether the interface
can
hit 150 or 133 or 100.

... apart from the burst speed which with drives with 16MB cache now
can be a significant factor, especially with video editing applications
(where
the
caching algorithms have a better chance because of the big files).
16MB bursting at 150MB/s is not insigificant.

I fail to see how it makes a difference with video editing, where you are
trying to stream several gigabytes of data.

But you are not. You don't load "several gigabytes of data" into memory
and
*then* start processing it. True, the data comes in large chunks - but
not
gigabytes. Its processed piece by piece.

And your point here is? It's a continuous stream, not bursts, so what
difference does the larger cache make?

How much real-world difference do you see between a drive with a 16 meg
cache and an otherwise identical drive with a 2 meg cache?

"Some"?

How much? Can you put a number on it?

With PATA and two drives per channel, it's possible for both drives
together
to fill a 150 MB/sec channel but SATA allows only one per channel so
that's
not an issue.

In any case, some use a bridge chip, others don't. IIRC Seagate is
not
using a bridge chip. I don't recall what WD is doing, but their
Raptors
outperform any SATA drive from any other manufacturer, although the
Hitachi
7K250 and 7K400 come close, so whether they're using a bridge chip or
not
clearly doesn't make any real-world difference.

The Raptors have a bridge chip too. They are basically SCSI drives
with an adapter chip on them.

I see. So you are claiming that they have a SCSI interface bridged to
SATA?

Yes. I am not sure to what extent the SCSI interface remains in tact.
But I know they are not "native" SATA drives, i.e. they are something else
with
a bridge chip. And the "something else" was originally a 37Gb or 74GB
SCSI drive.

If you investigate farther you will find that the mechanical parts, the
motor, etc are typical of what one would find in an enterprise-grade SCSI
drive but the electronics are IDE bridged to SATA.

Or are you just saying that being constructed to the same quality
standards
as server-grade drives somehow makes them have a different interface?

Nope. See above.

I saw above. It appears to be in error.

Chip

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)