How do I tell Firewire 400 vs 800 ports

It should say what types of ports they are in your System Profiler.

Also the ports don't look exactly the same. The connection is a little different.

lenn

Conness wrote:

I have the white 20" iMac, about a year old or so.

White 20" iMacs have FW400 only (two ports). The white 24" and
all ALU iMacs have both FW400 and FW800 (one of each):

http://support.apple.com/specs/imac/iMacLate2006.html

You can use a FW800 external drive on your FW400 ports (at FW400
speed, of course). Just use a 9-pin to 6-pin firewire adapter cable.

Looby

You'll be running at the speed of your iMac's firewire 400 ports.

lenn

You can't get a 400-to-800 adapter that will speed things up for you. The port can only operate at 400 Mbps.

That said, it hardly matters. If you're only using one disk at a time, it is not likely to matter. The theoretical maximum transfer rate for a 7200 RPM disk is something like 55 MB/sec, but in practice you rarely see more than half that. The 400Mbps FireWire connection is operating faster than the hard disk reads and writes.

J D McIninch wrote:

That said, it hardly matters. If you're only using one disk at a time, it is not likely to matter. The theoretical maximum transfer rate for a 7200 RPM disk is something like 55 MB/sec, but in practice you rarely see more than half that.

I'm not aware of any "theoretical maximum" transfer rate, but in any case,
55 MB/s is SLOOOOOW by today's standards. Many ordinary, garden-variety,
7200 rpm SATA drives routinely deliver anywhere from 80 to 120 MByte/sec
sustained R/W transfer rates -- and according Seagate technical forecasts,
the present technology (perpendicular recording / GMR heads) is nowhere
near its limit. Speed/density will continue to grow by leaps and bounds.

[Actual performance measurements for Real™ disk drives|http://www.tomshardware.com/charts/3-5-hard-drive-charts/maximum-read-tr ansfer-rate,666.html?p=1826%2C1782%2C1844%2C1772%2C1845%2C1780%2C1799%2C1777%2C1 803%2C1798%2C1788%2C1815%2C1812%2C1794%2C1805%2C1791%2C1809%2C1833%2C1807%2C1766 %2C1842]

Looby