D–10 PALcode Restrictions and Guidelines
21264/EV68A Hardware Reference Manual

Restriction 9 : PALmodeIstream Address Ranges

Bad_interrupt_flow_entry:
ADDQ R31,R31,R0
STF Fa,(Rb) ; This STF might not undergo adirty source register
; check and might give wrong results
ADDQ R31,R31,R0
ADDQ R31,R31,R0
................................
Good_interrupt_flow_entry:
ADDQ R31,R31,R0; Enables FP dirty source register
; check for (PC[1:0] == 00)
ADDQ R31,R31,R0; Enables FP dirty source register
; check for (PC[1:0] == 01)
ADDQ R31,R31,R0; Enables FP dirty source register
; check for (PC[1:0] == 10)
ADDQ R31,R31,R0; Enables FP dirty source register
; check for (PC[1:0] == 11)
ADDQ R31,R31,R0
STF Fa,(Rb); This STF willsuccessfully undergo
; a dirty source register check
ADDQ R31,R31,R0
ADDQ R31,R31,R0
D.6 Restriction 9 : PALmode Istream AddressRanges
PALmode[physical]Istream addresses must ensure proper sign extension for the
selectedvalue of I_CTL[VA_48]. When I_CTL[VA_48]is clear, indicating 43-bit vir-
tual addressformat, PALmode[physical] Istream addresses must sign-extend address
bitsa bovebit 42 although the physical address range is 44 bits. An illegal address can
only be generated by a PALmodeJSR-type instruction or a HW_RET instruction
returningto a PALmode address.
D.7 Restriction 10: Duplicate IPR Mode Bits
The virtualaddress size is selectable by programming IPR bits I_CTL[VA_48]
and VA_CTL[VA_48]. These bit valuesshould usually be equal when operating in
native(virtual) mode. The I_CTL[VA_48] bit determinesthe DTB double3/double4
PALcodeentry, the JSR mispredict comparison width, the VPC address generation
width,the Istream ACV limits, and the IVA_FORM format selection. The
VA_CTL[VA_48] bit determinesthe VA_FORM format selection and the Dstream
ACV limits. IPR mode bits I_CTL[VA_FORM_32]and VA_CTL[VA_FORM_32]
shouldbe consistent when executing in native mode.