AAEON PCM-5895 Rev.B - Manual (Page 43)

C o m p a c t B o a r d P C M - 5 8 9 5 R e v . B
Chapter 2 Quick Installation Guide 2- 30
The problem is related to the fact that one device is on the cable and the
other is populated on the motherboard.
A 40-pin cable has PDIAG- available on all its connectors. Therefore,
PDIAG- may be signaled from the cable-based HDD, through the
motherboard, and to the CF (or vice versa).
Unfortunately, the higher UDMA modes cannot be supported on a 40-pin
cable.
An 80-pin cable is typically marked with the specific connectors intended
for motherboard and drives. The PDIAG- signal is allowed to travel
between the two drives on the cable, but is not connected to the
motherboard. Inside the cable’s motherboard connector, the PDIAG- signal
is disconnected from the two drives, and grounded for the motherboard. As
a result, the PDIAG- signal cannot travel between the HDD (on the cable)
and a CF (on the motherboard).
There are three options for supporting configurations with both HDD and
CF:
1) Use a 40-pin cable. This solution limits the user to the lower UDMA
speeds.
2) Abandon the CF socket on the LX DB800 baseboard and use a CF
adapter that attaches directly to the 80-pin cable. This solution allows the
HDD to operate at the higher UDMA speeds and also maintains support for
the 80-pin cable detection.
3) Modify an 80-pin cable (or build a modified cable). Cutting off the host
end of the 80-pin cable at the point where it attaches to the first drive
connector allows the PDIAG- signal to pass from the HDD to the CF socket.
This also removes the hardware support for detecting the presence of the
80-pin cable, and requires the BIOS be modified so that 80-pin support is
the default.
2.38 PCI-104 Slot (PCI1)
Standard Specification
2.39 PCI-104 Slot (PCI2)
Standard Specification