Signal
Name
I/O
Type
Default
Mode
Ball
Coun
t
Default
Direction
and Logic
State
Power
Well
Internal/
External
Resistor Pull-
Up/Down
Description
GPIO53
I/O
Native
1
O (High)
CORE
Platform
Dependant. Weak
internal pull-up
General Purpose I/O Port 53. Not
Multiplexed.
3
External platform dependent.
DMI Coupling Strap.
0 AC Coupling (Pull-Down Required)
1 DC Coupling (Default)
GPIO54
2
I/O
Native
1
I
CORE
General Purpose I/O Port 54. Not
Multiplexed
3
GPIO55
I/O
Native
1
O (High)
CORE
Weak internal
pull-up
General Purpose I/O Port 55. Not
Multiplexed.
3
Strap for BIOS Boot-Block Update
Scheme. This mode allows the PCH to
swap the Top-Block in the SPI (the boot
block) with another location.
GPIO55
0 Enable Top-Block Swap (Pull-down
required)
1 Disable Top-Block Swap (Default)
The internal pull-up is disabled after
PLTRST# deasserts. If the signal is
sampled low, this indicates that the
system is strapped to the “Top-Block
Swap” mode (the PCH inverts A16 for all
cycles targeting BIOS space).
The status of this strap is readable via
the Top Swap bit (Chipset Config
Registers:Offset 3414h:bit 0). Software
will not be able to clear the Top-Swap bit
until the system is rebooted without
GPIO55 being pulled down.
GPIO56
I/O
Native
1
I
SUS
General Purpose I/O Port 56. Not
Multiplexed.
3
GPIO57
I/O
GPI
1
I
SUS
General Purpose I/O Port 57. Not
Multiplexed.
SML1CLK/
GPIO58
I/O
SML1CL
K
1
I
SUS
When SMBUS:
External pull-up
required
System Management Link 1 Clock.
SMBus link to external BMC.
External pull-up resistor to VCCSUS3P3 is
required.
Resistor value should be calculated based
on the bus load, refer to the Platform
Design Guide.
If SML1CLK interface is not used, the
signals can be used as GPIO Port 58.
OC0#/
GPIO59
2
I/O
OC0#
1
I
SUS
Overcurrent Indicators. These signals set
corresponding bits in the USB controllers
to indicate that an overcurrent condition
has occurred.
OC[3:0]# may optionally be used as
GPIO Ports [42,41,40,59].
OC# pins are 3.3V and NOT 5 V tolerant.
OC# pins must be shared between ports
OC#[3:0] can only be used for EHCI
controller #1
continued...
Crystal Forest—Technical Reference
Intel
®
Xeon
®
Processor E3-1125C with Intel
®
Communications Chipset 8910 Development Kit
User Guide
October 2012
50
Order No.: 328009-001US