You check the chipset details for the motherboard.
For example, it could be 945G and ICH7. The diagram
here, lists four SATA ports.
http://techreport.com/r.x/pentiumd-820/945g-block-diagram.gif
They may have equipped just connectors SATA0 and
SATA2, so the drives both show as fake "Master"
in software. The other connectors may not have been
soldered in, to save a few pennies.
SATA0 Master \__ For IDE ribbon cable emulation purposes
SATA1 Slave /
SATA2 Master \__ For IDE ribbon cable emulation purposes
SATA3 Slave /
This is an example of a 945G board. The 945G is the one
underneath the tall aluminum heatsink. The ICH7 is the one
near the four SATA connectors. Since the ICH7 chip is bare,
and has no heatsink on top, that allows the user to read the
number off the top, and verify the chip name. Perhaps
the number is 82801G or 82801GR or something.
http://web.archive.org/web/20051013082857/http://www.intel.com/design/motherbd/cz/pix/d945gcz_lg.jpg
Note that, in that motherboard example, the number was erased
from the top of the chip. The actual board, you'll be able
to read a number off the top.
It should be as easy to read, as this one.
http://img.tomshardware.com/us/2006/01/28/intel_ich7m.jpg
You can also use the SLxxx number, enter it on the ark.intel.com
site, and it'll give some more details.
http://ark.intel.com/search?q=sl8yb
You can also search using "ICH7" as a name, and try to locate
the most likely part number.
http://ark.intel.com/products/27679/Intel-82801GB-IO-Controller
Total # of SATA Ports 4
Integrated IDE 1 Channel
And that info, means a maximum of 6 drives can be connected
to the chip. Four SATA and two IDE. But only if the connectors
are soldered to the motherboard for it.
*******
When you ask a question like this, it helps to mention
the details of the computer, like Dell Dimension 5100 or whatever.
I can't be sure any of the above, is related to your computer.
Paul