Support Notes for Red Hat Enterprise Linux AS V.4 Update 4 for HP Integrity Servers

22. Output from the Management Processor (MP) serial ports may hang due to a failure to
reassert a transmit empty interrupt in the MP UART. When used as a serial console, this
output hang may lead to a hang during Linux boot. This condition may occur on any low-end
Integrity system using the MP console port as the Linux system console. This problem does
not exist on mid-range and high-end Integrity platforms.
When rebooting the system, the user should either manually confirm the system has booted,
or use scripts to track the system boot on the serial console and automatically intervene as
necessary. The only intervention required to continue the boot process is to send a character
to produce a receiver interrupt on the console UART (for example, pressing a key). Note
that while experiencing this console hang is rare, it can happen multiple times on the same
boot cycle.
23. Installation to a software RAID 6 volume may result in a kernel panic. If this occurs, try
using a different RAID type such as RAID 5.
24. The cdrecord program may hang when burning a CD-RW disk with unsupported media
using certain models of CD/DVD-ROM Combo and DVD+RW drives shipped in rx1600,
rx1620, rx2600, rx2620, and rx4640 servers.
Use only approved HP CD-RW media to prevent burn hangs. Try different brands of media
if HP media is not available.
25. The ELILO bootloader can pass command-line options to the Linux kernel. The max_addr=
and mem= options limit the amount of memory used by the kernel.
Some versions of the kernel handle these arguments incorrectly, resulting in an MCA that
crashes the system during boot. If the system boots successfully, there is no risk of a crash
due to this problem.
Booting with max_addr= or mem= is sometimes useful for debugging problems, but is not
a tested feature. A similar effect can be achieved by deconfiguring (with the EFI dimmconfig
command) or physically removing DIMMs.
26. This issue affects RHEL4 U3 and RHEL4 U4 on Itanium systems with more than 64 CPU
cores or threads.
The standard RHEL4 Itanium kernel supports up to 64 CPUs. RHEL4 can be installed on a
larger system, but only 64 CPUs will be used.
Each thread on each core counts as a CPU for this purpose. Configurations with more than
64 cores or 64 threads require the largesmp kernel in order to use all the threads.
The following table shows the maximum CPU core and thread configurations for
sx2000-based systems. If CPU threads are disabled, the Cores column applies. If threads are
enabled, the Threads column applies.
Threads (optional)CoresCPU SocketsCells
16841
321682
6432164
8040205
12864328
14472369
2561286416
rx7640 and rx8640 systems are limited to two and four cells, respectively, so they never need
the largesmp kernel.
Known Issues 11