Compaq EV68A Opcodes Reserved for PALcode, Hwst Instruction, Hwld Instruction Fields Descriptions

Opcodes Reserved for PALcode

Figure 6–1 HW_LD Instruction Format

31	26 25		21 20	16 15	13 12 11	0
	OPCODE	RA	RB			DISP
TYPE
LEN								FM-05654.AI4

Table 6–3describes the HW_LD instruction fields.

Table 6–3 HW_LD Instruction Fields Descriptions

Extent	Mnemonic	Value	Description
[31:26]	OPCODE	1B16	The opcode value.
[25:21]	RA	—	Destination register number.
[20:16]	RB	—	Base register for memory address.
[15:13]	TYPE	0002	Physical — The effective address for the HW_LD instruction is physical.
		0012	Physical/Lock — The effective address for the HW_LD instruction is
			physical. It is the load lock version of the HW_LD instruction.
		0102	Virtual/VPTE — Flags a virtual PTE fetch (LD_VPTE). Used by trap logic
			to distinguish a single TB miss from a double TB miss. Kernel mode access
			checks are performed.
		1002	Virtual — The effective address for the HW_LD instruction is virtual.
		1012	Virtual/WrChk — The effective address for the HW_LD instruction is
			virtual. Access checks for fault-on-read (FOR), fault-on-write (FOW), read
			and write protection.
		1102	Virtual/Alt — The effective address for the HW_LD instruction is virtual.
			Access checks use DTB_ALT_MODE IPR.
		1112	Virtual/WrChk/Alt — The effective address for the HW_LD instruction is
			virtual. Access checks for FOR, FOW, read and write protection. Access
			checks use DTB_ ALT_MODE IPR.
[12]	LEN	0	Access length is longword.
		1	Access length is quadword.
[11:0]	DISP	—	Holds a 12-bit signed byte displacement.

6.4.2 HW_ST Instruction

PALcode uses the HW_ST instruction to access memory outside the realm of normal Alpha memory management and to do special forms of Dstream store instructions. Data alignment traps are inhibited for HW_ST instructions. Figure 6–2shows the HW_ST instruction format.

Figure 6–2 HW_ST Instruction Format

31	26 25		21 20	16 15	13 12 11	0
	OPCODE	RA	RB			DISP
TYPE
LEN								FM-05654.AI4

6–4 Privileged Architecture Library Code 21264/EV68A Hardware Reference Manual