Intel MPCBL0001 manual Reset Logic, Hard Reset Request, Soft Reset Request

Hardware Management Overview

3.12.1Reset Logic

The following topics describe the two types of reset requests and the boot relationships among them. The two types of reset requests available on the MPCBL0001 are:

•Hard reset request (always results in a cold boot)

•Soft reset request (can result in either a warm or cold boot)

A hard reset request occurs whenever the processor Reset line is asserted and then deasserted. A soft reset occurs whenever an assertion occurs on the processor Init line. Whenever a soft reset request occurs, the BIOS checks two memory locations to determine whether to initiate a warm boot while leaving main memory intact or a cold boot that clears memory.

Whenever the BIOS detects that the reset is either a hard reset or a cold boot, it specifically clears the memory location 40h:72h so it does not contain a 1234h. Under warm boot conditions, this memory location contains a 1234h (the developer’s application writes this value in this location [using /dev/mem] when it is started). If a hard reset occurs (as defined in the hard reset topic below), it is certain that the 40h:72h location contains a non-1234h value.

3.12.2Hard Reset Request

A Hard Reset, or CPU Reset, is defined as the assertion of the processor reset signal (see Table 24, “Reset Request” on page 58). This initializes the processor state and registers, disables internal caches, and causes the processor to unconditionally begin execution from the reset vector. A hard reset is initiated by the following events:

1.A power up of the SBC. The SMC enables the onboard power supplies.

2.The SMC negates the ICH3_PWROK signal (see Note below).

3.A “reset” command from the Port CF9h I/O register (refer to the “Intel® 82801CA I/O Controller Hub 3 (ICH3-S) Datasheet” for information about this register).

4.Watchdog timer (WDT #1) expires and is configured to initiate a hard reset. See “Watchdog Timers (WDTs)” on page 62 for more information.

5.Watchdog timer (WDT #3) expires after failure to perform the first instruction fetch.

6.A command (cmmset -l bladex -d powerstate -v reset) is issued from MPCMM0001.

Note: The IPMC can negate the dedicated signal ICH3_PWROK to initiate a processor reset. ICH3_PWROK indicates whether power is OK. If the IPMC deasserts ICH3_PWROK, the hardware asserts the processor reset lines.

3.12.3Soft Reset Request

The assertion of the processor’s INIT signal causes a soft reset or “CPU INIT” (see Table 24, “Reset Request” on page 58). The ICH3 is normally responsible for driving the INIT signal. A CPU INIT event causes the processor(s) to fetch the reset vector at the next instruction boundary. The majority of the processor and all of the cache states are unaffected by an INIT event.

After the INIT event, hardware may be reset (or not reset) under BIOS control. PCI buses are reset using their respective bridge control registers. This signal is then level translated to the processor compatible signal level. INIT may be caused by the following events:

Intel NetStructure® MPCBL0001 High Performance Single Board Computer 57

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