Why are SATA drives faster than PATA when parallel ports are faster than serial?

Why are SATA drives faster than PATA when parallel ports are faster
than serial?

Thanks.

?http://en.wikipedia.org/wiki/Serial_ATA

peter

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"Bob" wrote in message
...
Why are SATA drives faster than PATA when parallel ports are faster
than serial?

Thanks.

Bob wrote:
Why are SATA drives faster than PATA when parallel ports are faster
than serial?

Thanks.

Parallel ATA has a "bad" design scheme, of supporting two drives per cable.

That compromises signal integrity (reflections off the middle
connector and stub capacitance).

If PATA only supported one drive, you could use differential signaling
on the ribbon cable (with termination resistors at the end, for good
signal quality), and get higher performance than SATA. But where would
the fun be in that ?

SATA is kinda a dopey standard, in that the data cable is 7 signals,
and the power is 15 signals. The design seems to be predicated on
using a "wafer" connector, and is optimized for supporting server backplanes
and "snapping" drives into place. That means the connector was
designed, to make servers easier to design. Designing it for
the desktop was an afterthought. The fact that the first
generation SATA cables would fall out, shows how much attention
was paid to desktops. That has since been fixed.

I still wouldn't give them high marks for the connector. On some
motherboards, the SATA connector on the motherboard has been ripped
right off the motherboard, by plugging and unplugging. When
was the last time that happened to a ribbon cable connector ?

Paul

"Bob" wrote in message
...
Why are SATA drives faster than PATA when parallel ports are faster
than serial?

Thanks.

Actually, serial can be, and is, much faster than parallel.
The standard serial ports have been replaced with USB,
which is serial. Serial can reach speeds impossible with
parallel. The problem with parallel is that, with increased
speeds, bit delays in signal propogation become a
problem. For each byte of data, signal pulses for each
line in parallel transmission have to arrive simultaneously.
At slower speeds the pulse widths are sufficient that a slight
delay in one or more of the bits may not be significant. At
high speeds, with sub-nanosecond pulse widths, controlling
the propogation delays on each line becomes difficult. This
is also why PCI is being replaced by PCIe. If you look at
the conductive traces on a PCI motherboard, you will notice
a lot of zig-zagging. This is to delay signals on the shorter
more direct lines.

Getting back to SATA, SATAIII speeds would be impossible
with parallel connections in a PC environment.

On 9/22/2010 5:34 PM, Bob wrote:
Why are SATA drives faster than PATA when parallel ports are faster
than serial?

Thanks.

"Parallel" and "serial" computer ports have nothing to do with PATA and
SATA ports other than possibly existing in the same computer. The real
limitation of transferring signals in parallel lies in synchronizing them
perfectly (a parallel port is nothing more than a number of serial ports
expected to work in unison). In some circumstances, SCSI Ultra-640 for
example, it is possible to push data at 640MB/s which is much faster than
SATA achieves now or is likely to in the near future. The problem with this
uber-fast parallel format is that nobody outside of a narrow industry niche
would be willing to bear the cost of using it as a PC standard and for this
reason the standard was pretty much ignored by the industry and production
parallel SCSI devices really didn't progress beyond Ultra-320 (which isn't
a slouch when it comes to speed despite being virtually ancient history!)

"Ian D" wrote in message
...

"Bob" wrote in message
...
Why are SATA drives faster than PATA when parallel ports are faster
than serial?

Thanks.

Actually, serial can be, and is, much faster than parallel.

Precicely why we should stop buying multi-core parallel processors and push
the manufacturers to go back to the single threaded GHz wars. Rant over!

On Sep 22, 5:46*pm, "Ian D" wrote:
Actually, serial can be, and is, *much faster than parallel.
The standard serial ports have been replaced with USB,
which is serial. *Serial can reach speeds impossible with
parallel. *The problem with parallel is that, with increased
speeds, bit delays in signal propogation become a
problem. *For each byte of data, signal pulses for each
line in parallel transmission have to arrive simultaneously.

thanks for the informative answer.

And good question, Bob. I had always wondered that myself, since
theoretically, parallel anything should be faster than serial anything.

"Bob" wrote in message
...
Why are SATA drives faster than PATA when parallel ports are faster
than serial?

Thanks.


Because parallel ports are NOT axiomatically faster than serial ports.