Intel 521 Data Sheet - Page 70

Land Listing and Signal Descriptions Table 4-3. Signal Description (Sheet 5 of 8) Name Type Description IGNNE# INIT# ITP_CLK[1:0] LINT[1:0] LL_ID[1:0] LOCK# MCERR# MSID[1:0] Input IGNNE# (Ignore Numeric Error) is asserted to force the processor to ignore a numeric error and continue to execute noncontrol floating-point instructions. If IGNNE# is de-asserted, the processor generates an exception on a noncontrol floating-point instruction if a previous floating-point instruction caused an error. IGNNE# has no effect when the NE bit in control register 0 (CR0) is set. IGNNE# is an asynchronous signal. However, to ensure recognition of this signal following an Input/Output write instruction, it must be valid along with the TRDY# assertion of the corresponding Input/Output Write bus transaction. Input INIT# (Initialization), when asserted, resets integer registers inside the processor without affecting its internal caches or floating-point registers. The processor then begins execution at the power-on Reset vector configured during power-on configuration. The processor continues to handle snoop requests during INIT# assertion. INIT# is an asynchronous signal and must connect the appropriate pins/lands of all processor FSB agents. If INIT# is sampled active on the active to inactive transition of RESET#, then the processor executes its Built-in Self-Test (BIST). Input ITP_CLK[1:0] are copies of BCLK that are used only in processor systems where no debug port is implemented on the system board. ITP_CLK[1:0] are used as BCLK[1:0] references for a debug port implemented on an interposer. If a debug port is implemented in the system, ITP_CLK[1:0] are no connects in the system. These are not processor signals. Input LINT[1:0] (Local APIC Interrupt) must connect the appropriate pins/lands of all APIC Bus agents. When the APIC is disabled, the LINT0 signal becomes INTR, a maskable interrupt request signal, and LINT1 becomes NMI, a nonmaskable interrupt. INTR and NMI are backward compatible with the signals of those names on the Pentium processor. Both signals are asynchronous. Both of these signals must be software configured via BIOS programming of the APIC register space to be used either as NMI/INTR or LINT[1:0]. Because the APIC is enabled by default after Reset, operation of these signals as LINT[1:0] is the default configuration. The LL_ID[1:0] signals are used to select the correct loadline slope for the Output processor. LL_ID[1:0] = 00 for the Pentium 4 processor in the 775-land package. Input/ Output LOCK# indicates to the system that a transaction must occur atomically. This signal must connect the appropriate pins/lands of all processor FSB agents. For a locked sequence of transactions, LOCK# is asserted from the beginning of the first transaction to the end of the last transaction. When the priority agent asserts BPRI# to arbitrate for ownership of the processor FSB, it will wait until it observes LOCK# de-asserted. This enables symmetric agents to retain ownership of the processor FSB throughout the bus locked operation and ensure the atomicity of lock. Input/ Output MCERR# (Machine Check Error) is asserted to indicate an unrecoverable error without a bus protocol violation. It may be driven by all processor FSB agents. MCERR# assertion conditions are configurable at a system level. Assertion options are defined by the following options: • Enabled or disabled. • Asserted, if configured, for internal errors along with IERR#. • Asserted, if configured, by the request initiator of a bus transaction after it observes an error. • Asserted by any bus agent when it observes an error in a bus transaction. For more details regarding machine check architecture, refer to the IA-32 Software Developer's Manual, Volume 3: System Programming Guide. Output MSID[1:0] are provided to indicate the market segment for the processor and may be used for future processor compatibility or for keying. 70 Datasheet