AMD-X5-133ADW AMD [Advanced Micro Devices], AMD-X5-133ADW Datasheet - Page 53

• Manufacturer Part Number: AMD-X5-133ADW
• Manufacturer: AMD [Advanced Micro Devices]

4. The SMBASE Relocation feature affects the way
Note: The execution of an IRET instruction enables
Non-Maskable Interrupt (NMI) processing.
7.9.3 Halt during SMM
HALT should not be executed during SMM, unless in-
terrupts have been enabled. Interrupts are disabled on
entry to SMM. INTR and NMI are the only events that
take the CPU out of HALT within SMM.
7.9.4 Relocating SMRAM to an Address above
Within SMM (or Real mode), the segment base registers
can be updated only by changing the segment register.
The segment registers contain only 16 bits, which allows
only 20 bits to be used for a segment base address (the
segment register is shifted left 4 bits to determine the
segment base address). If SMRAM is relocated to an
address above 1 Mbyte, the segment registers can no
longer be initialized to point to SMRAM.
These areas can still be accessed by using address
override prefixes to generate an offset to the correct
address. For example, if the SMBASE has been relo-
cated immediately below 16 Mbytes, the DS and ES
registers are still initialized to 0000 0000h. Data in SM-
RAM can still be accessed by using 32-bit displacement
registers
move esi,OOFFxxxxh
move ax,ds:[esi]
EXT = 0
EXT = 1
Notes:
1. Bit 19 in TR5 is EXT. If EXT = 0, TR4 has the standard 486 processor definition for write-through cache.
2. The values of Set State are: 00 = Invalid; 01 = Exclusive; 10 = Modified; 11 = Shared.
Write-Through
Write-Back
pushed onto the stack. If the offset of the interrupted
procedure is greater than 64 Kbytes, it is not possi-
ble for the interrupt/exception handler to return con-
trol to that procedure. (One work-around is to
perform software adjustment of the return address
on the stack.)
the CPU returns from an interrupt or exception dur-
ing an SMI handler.
Notes:
1. The values of STn and ST3–ST0 are: 00 = Invalid; 01 = Exclusive; 10 = Modified; 11 = Shared.
2. During a cache look-up, bit 11 is read only and always 0. The bit is read/write otherwise.
1 Mbyte
used
Not
31
30–29
STn
Not used
31–20
Rsvd.
28
;64K segment
27–26
immediately below 16M
ST3
Ext
19
Table 18. Test Register TR5 Bit Descriptions
Table 17. Test Register TR4 Bit Descriptions
25–24
ST2
Set State
18–17
Not used
Tag
Am5
23–22
ST1
X
PRELIMINARY
86 Microprocessor
21–20
ST0
Reserved
16
8
The Cache Test Registers for the Am5
sor are the same test registers (TR3, TR4, and TR5)
provided in Am486 microprocessors. TR3 is the cache
test data register. TR4, the cache test status register,
and TR5, the cache test control register, operate togeth-
er with TR3.
If WB/WT meets the necessary setup timing and is sam-
pled Low on the falling edge of RESET, the processor
is placed in Write-through mode and the test register
function is identical to the Am486 microprocessors. If
WB/WT meets the necessary setup timing and is sam-
pled High on the falling edge of RESET, the processor
is placed in Write-back mode and the test registers TR4
and TR5 are modified to support the added write-back
cache functionality. Tables 17 and 18 show the individ-
ual bit functions of these registers. Sections 8.1 and 8.2
provide a detailed description of the field functions.
Note: TR3 has the same functions in both Write-through
and Write-back modes.These functions are identical to
the TR3 register functions provided by Am486 micro-
processors.
8.1
This section includes a detailed description of the bit
fields defined for TR4.
Note: Bits listed in Table 17 as Reserved or Not used
are not included in these descriptions.
Reserved
Tag (bits 31–12): Read/Write, always available in
Write-through mode. Available only when EXT=0 in
TR5 in Write-back mode. For a cache write, this is
the tag that specifies the address in memory. On a
cache look-up, this is tag for the selected entry in the
cache.
19–16
TEST REGISTERS 4 AND 5
MODIFICATIONS
TR4 Definition
Not used
15–12
15–12
Not used
Index
Index
11–4
11
0
Valid
Valid
10
Entry
Entry
3–2
LRU
LRU
9–7
X
86 microproces-
Valid
Valid
6–3
(rd)
(rd)
AMD
Control
Control
1–0
used
used
2–0
Not
Not
53