AMD-K6-2ESLASH233AMZ datasheet(243/332 Pages) AMD

243 / 332 page

Chapter 11

System Management Mode (SMM)

225

22529B/0—January 2000

AMD-K6™-2E Processor Data Sheet

Preliminary Information

Table 44 shows the format of the I/O trap restart slot.

The processor initializes the I/O trap restart slot to 0000h upon

entry into SMM. If SMM was entered due to a trapped I/O

instruction, the processor indicates the validity of the I/O

instruction by se tti ng or cleari ng bit 1 of the I/O trap

doubleword at offset FFA4h in the SMM state-save area. The

SM M s e rv i c e ro uti n e s h o u l d te st bi t 1 o f th e I /O trap

doubleword to determine if a valid I/O instruction was being

executed when entering SMM and before writing the I/O trap

restart slot. If the I/O instruction is valid, the SMM service

routine can safely rewrite the I/O trap restart slot with the value

00FFh, which causes the processor to re-execute the trapped I/O

instruction when the RSM instruction is executed. If the I/O

instruction is invalid, writing the I/O trap restart slot has

undefined results.

If a second SMI# is asserted and a valid I/O instruction was

trapped by the first SMM handler, the CPU services the second

SMI# prior to re-executing the trapped I/O instruction. The

second entry into SMM neve r has bit 1 of th e I/O trap

doubleword set, and the second SMM service routine must not

rewrite the I/O trap restart slot.

During a simultaneous SMI# I/O instruction trap and debug

breakpoint trap, the AMD-K6-2E processor first responds to the

SMI# and postpones recognizing the debug exception until

after returning from SMM via the RSM instruction. If the debug

registers DR3–DR0 are used while in SMM, they must be saved

and restored by the SMM handler. The processor automatically

saves and restores DR7–DR6. If the I/O trap restart slot in the

SMM state-save area contains the value 00FFh when the RSM

instruction is executed, the debug trap does not occur until

after the I/O instruction is re-executed.

Table 44. I/O Trap Restart Slot

31–16

15–0

Reserved

I/O Instruction restart on return from SMM:

0000h = Execute the next instruction after the trapped I/O

00FFh = Re-execute the trapped I/O instruction

AMD-K6-2E/233AMZ Datasheet(PDF) 243 Page - Advanced Micro Devices

AMD-K6-2E/233AMZ Datasheet(HTML) 243 Page - Advanced Micro Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL