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IDE has been around since 1986, and Apple has been using IDE drives
in Macs since 1995. Apple first used SATA drives in 2003, and as of
2006 they are in use across the Macintosh line (more on
that below).
I'm a low-end Mac user by necessity, and all of the Macs I use
regularly have IDE drives. I started to get an inkling that something
was up a few months ago when I tried to find a hard drive deal for my
266 MHz WallStreet
PowerBook - and DealMac
didn't list any IDE notebook drives. This morning I
checked DealMac for 3.5" hard drives, and received the message, "No
recent deals found for IDE Hard Drives."
It's not that IDE hard drives aren't still available - they are, but
the market has shifted to SATA, so there's little point running deals
on IDE drives when people are looking for SATA drives.
On top of that, many new hard drives aren't available for IDE, just
for SATA.
SATA for Older Macs
That got me to wondering if it might not make more sense to put a
SATA controller card in one of my G4 Power Macs so I could benefit from
the newest, fastest, highest capacity, and best deal hard drives.
No luck at DealMac, which only lists an eSATA adapter in its listing
of
SATA Controller Card Deals. Without SATA, that adapter does no
good. On to Other World Computing, a company that knows and loves older
Macs. Its listing of
SATA cards for PCI Macs starts at $64 for a FirmTek card that
works in any Mac with PCI slots and even supports Mac OS 8.x.
When you're looking at computers that sell for $200 to $300 on the used
market, it's not easy to justify that expense. On the other side,
you can buy a dual 1.8
GHz Power Mac G5 for $400 and have SATA built right in - along with
more processing power (my fastest is a dual 1.6 GHz G4), a faster
memory bus, support for 4 GB of RAM, and better graphics (my best
video card is a Radeon 9000; a G5 Power Mac would give me GeForce
5200).
Makes you think twice about upgrading the old G4 Power Mac - not
that I can afford either at present. Still, it's nice to know the
options for future reference.
Another Option
Of course, a third alternative is an Intel-based Mac mini. For under
$600, I could have a brand new 2.26 GHz dual-core Mac mini with 2 GB of
RAM, a 160 GB hard drive, GeForce 9400M graphics, and Mac OS X 10.6 "Snow Leopard".
I'm already using OS X 10.5
"Leopard" on one of my Power Macs, and it would be trivial to swap
in a Mac mini. I can't even imagine the processing power compared with
dual 1.6 GHz G4 CPUs.
On the used side, I could buy a 1.83 GHz Core Duo Mac mini for about
the same price as that dual 1.8 GHz Power Mac G5 (less when you factor
in shipping). Add $25
for Snow Leopard, and I'd be quite a bit less "low end" than I am
today, even with the Intel GMA 950 graphics on the older Intel-based
minis.
Despite the fact that any of these options are outside of my budget
at present, it's good to have a benchmark when planning ahead. I
suspect that I won't be doing much in the way of upgrading my wonderful
old Power Macs and will eventually be buying an Intel-based Mac mini as
my main Leopard machine. Although I like expansion slots and drive
bays, realistically the Mac mini provides what I need.
SCSI vs. IDE
Apple was the first personal computer maker to adopt SCSI hard
drives (starting in 1986 with the Mac Plus) and the last to adopt IDE
hard drives (in 1995 with the Quadra 630 and PowerBook 150).
SCSI was and remains a superior protocol. With IDE/ATA drives, the
computer's CPU is involved in a lot more drive management duties. With
SCSI, most of those housekeeping details are handled by the SCSI chips,
which are independent controllers. You can copy files from one SCSI
device to another with no need to communicate with the CPU.
However, IDE has one huge advantage over SCSI: It's cheaper. Because
it doesn't requires a SCSI controller, the controller board on the
drive itself costs less to make, so in cases where the same exact
mechanism is available for both protocols, the IDE drive will be
cheaper - usually a lot cheaper.
Back in 1986, when the first SCSI Mac and the first IDE PCs came to
market, 80386 CPUs were the top end of the market. 16 MHz 386 CPUs that
had to manage the hard drive, knowing what files were stored on it and
which tracks and sectors they occupied - details handled by SCSI. This
took its toll on overall system performance, but at CPUs got faster and
more powerful, CPUs needed to dedicate a smaller and smaller percentage
of their power to the drive bus.
When Apple began the transition to IDE in 1995, it was used on its
low-end consumer models, both of which ran at 33 MHz. IDE didn't come
to the Power Mac line until late 1997, when the Beige G3 became the first "pro"
Mac to ship with an IDE hard drive - and even then SCSI remained an
option.
IDE vs. SATA
The IDE/ATA protocol advanced over the years, and the latest version
(ATA-7 or Ultra ATA/133) supports transfer rates up to 133 MB per
second, over eight times the bandwidth of the 16 MB/s ATA-1 through
ATA-3 standards.
Just as USB replaced older, slower serial and parallel protocols and
FireWire was designed to displace SCSI, Serial ATA (SATA) was designed
to move beyond parallel ATA. The original SATA specification has a
bandwidth of 150 MB/s, SATA 300 (a.k.a. SATA 2) doubled that, and the
third generation SATA specification, released in May 2009, doubles that
to provide 600 MB/s of bandwidth.
The biggest difference between SATA and IDE/ATA is the data
connection. Parallel ATA and SCSI drives use those wide, flat ribbon
cables most of us are familiar with. SATA, like USB and FireWire, uses
a lot less wires, and all three of these protocols use round cables
that are much easier to route inside your computer.
In the case of SATA, there are seven conductors - two pairs of data
lines and three grounds. The connector is much smaller than the ones
used for IDE drives (notebook IDE drives use a different, smaller
connector than 3.5" and larger IDE devices).
Unlike IDE, where a bus can support two drives (master and slave) on
a single cable, SATA is designed to use one cable per device, although
port expanders (or multipliers) have been developed to allow more than
one SATA device to connect to a single SATA controller port.
SATA has been around since 2003, and Apple was among the first
companies to embrace it. The first Power Mac G5, released in
June 2003, was the first Mac to use SATA. When Apple made the
transition from PowerPC CPUs to Intel CPUs in 2006, it moved the entire
Macintosh line to SATA.
SATA vs. FireWire vs. USB 3.0
Protocol MB/s Mb/s USB 1.1 1.5 12 FireWire 400 50 400 USB 2.0 60 480 FireWire 800 100 800 SATA 150 150 1200 SATA 300 300 2400 FireWire 3200 400 3200 SATA 600 600 4800 USB 3.0 600 4800
ATA protocol throughput is always rated in megabytes per
second (MB/s), while other serial protocols - such as USB and FireWire
- are rated on megabits per second (Mb/s). Here's a quick
comparison of total bandwidth. Note that in USB, no device can use all
available bandwidth.
In terms of bandwidth, among the protocols in widespread use today,
SATA 300 wins hands down with three times the bandwidth of FireWire
800, which itself has about 2.5 times the bandwidth of USB 2.0 for a
single drive (a USB device can only use about two-thirds of total
bandwidth). In theory, SATA wins hands down, although few devices can
saturate the FireWire 800 bus.
Another area of difference is bus power. SATA is strictly a data
bus; it is not designed to provide power to an attached device. USB has
a 5V power line that can provide up to 500 mA of current (2.5 Watts of
power) to a device, while FireWire can provide up to 30V of power,
although 9V to 12V is typical on laptops. In terms of power, FireWire
can supply up to 60 Watts, although 10 to 20 is more common.
USB 3.0, which will become widely available in 2010, is designed to
be more competitive, providing at least 4V and up to 900 mA of current
as well as additional data lines - USB 3.0 can send data over one set
of lines and receive over another, while earlier USB protocols cannot
send and receive concurrently.
Looking Ahead
In the short term, SATA 300 will continue to dominate inside the
computer, FireWire - despite the superiority of more intelligent
devices - will become increasingly marginalized, and SuperSpeed USB 3.0
will quickly become the norm for external devices that can benefit from
its greater bandwidth and/or power. iPhones and iPods will charge more
quickly, 3.5" bus-powered external drives may be possible, and
simultaneous send and receive will give it a real leg up over USB
2.0.
Longer term, I can see USB 3.0 replacing SATA inside your computer.
With SATA, you have two cables, data and power. With USB 3.0, there
will be sufficient bus power for most devices, eliminating another set
of cables inside your computer.
Looking at Apple's track record, I wouldn't be at all surprised to
see it among the first to offer USB 3.0 on its computers - and perhaps
the first to use it internally instead of SATA when native USB 3.0
drive mechanisms become available.
And in a few years, we may report, "SATA is dead. Long live USB
3.0!"
Dan Knight has been using Macs since 1986,
sold Macs for several years, supported them for many more years, and
has been publishing Low End Mac since April 1997. If you find Dan's articles helpful, please consider making a donation to his tip jar.
Links for the Day
Mac of the Day: Radius System 100, introduced 1995.03.27. An all-out system designed for graphics professionals.
