path: root/doc
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authorH. Peter Anvin <hpa@zytor.com>2009-05-18 13:42:19 -0700
committerH. Peter Anvin <hpa@zytor.com>2009-05-18 13:44:35 -0700
commit4826c90afd85d3bc8ee963de0bf1438340db865a (patch)
tree5975a83deef10ec240c35bcdafed5a168c49be55 /doc
parent208721a5fa25e5a12d31e7a51488bf5ea7e2a680 (diff)
Try to HLT the processor during idlesyslinux-3.81-pre4
Try to HLT the processor during idle. All the events we care about should have interrupts associated with them, except possibly the serial console. Try to deal with the serial console by waiting some time before going into HLT, and giving the user the option of enabling the serial console interrupt, on the assumption that the BIOS will simply IRET. Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'doc')
1 files changed, 12 insertions, 0 deletions
diff --git a/doc/syslinux.txt b/doc/syslinux.txt
index 94141415..f654bffd 100644
--- a/doc/syslinux.txt
+++ b/doc/syslinux.txt
@@ -339,6 +339,7 @@ SERIAL port [[baudrate] flowcontrol]
"flowcontrol" is a combination of the following bits:
0x001 - Assert DTR
0x002 - Assert RTS
+ 0x008 - Enable interrupts
0x010 - Wait for CTS assertion
0x020 - Wait for DSR assertion
0x040 - Wait for RI assertion
@@ -366,6 +367,17 @@ SERIAL port [[baudrate] flowcontrol]
ports detected by the BIOS. They may or may not correspond to
the legacy port values 0x3F8, 0x2F8, 0x3E8, 0x2E8.
+ Enabling interrupts (setting the 0x008 bit) may give better
+ responsiveness without setting the NOHALT option, but could
+ potentially cause problems with buggy BIOSes.
+NOHALT flag_val
+ If flag_val is 1, don't halt the processor while idle.
+ Halting the processor while idle significantly reduces the
+ power consumption, but can cause poor responsiveness to the
+ serial console, especially when using scripts to drive the
+ serial console, as opposed to human interaction.
CONSOLE flag_val
If flag_val is 0, disable output to the normal video console.
If flag_val is 1, enable output to the video console (this is