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參數(shù)資料
| 型號(hào)： | AM486DX2 |
| 廠商： | Advanced Micro Devices, Inc. |
| 英文描述： | Am5X86⑩ Microprocessor Family |
| 中文描述： | Am5X86⑩微處理器家族 |
| 文件頁數(shù)： | 29/67頁 |
| 文件大?。?/td> | 1613K |
| 代理商： | AM486DX2 |
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Am5
X
86 Microprocessor
29
AMD
PRELIMINARY
10
9
Data
HITM
EADS
INV
Read
BRDY
AHOLD
BLAST
ADS
W/R
M/IO
ADR
CLK
W n+4
W n
W n+8
W n+C
Figure 12. Snoop Hit Cycle with Write-Back
Note:
The circled numbers in this figure represent the steps in section 4.8.5.3.
1
7
8
5
4
6
3
2
CACHE
from CPU
to CPU
from CPU
Step 8 As an example, AHOLD is now removed. In the
next clock cycle, the current address of the
write-back access is driven onto the address
bus.
Step 9 The write-back access is finished when BLAST
and BRDY both transition to 0.
Step 10In the clock cycle after the final write-back
access, the snooping cache drives HITM back
to 1.
The status of the snooped and written-back line is now
either shared (INV = 0) or is changed to invalid (INV = 1).
4.8.6
Reordering of Write-Backs (AHOLD) with
BOFF
As seen previously, the Bus Interface Unit (BIU) com-
pletes the processor-initiated access first if the snooping
access occurs after the start of the processor-initiated
access. If the HITM signal occurs one clock cycle before
the ADS = 0 of the processor-initiated access, the write-
back receives priority and is executed first.
However, if the snooping access is executed after the
start of the processor-initiated access, there is a
methodology to reorder the access order. The BOFF
signal delays outstanding processor-initiated cycles so
that a snoop write-back can occur immediately (see
Figure 13).
Scenario
: If there are outstanding processor-initiated
cycles on the bus, asserting BOFF clears the bus pipe-
line. If a snoop causes HITM to be asserted, the first
cycle issued by the microprocessor after deassertion of
BOFF is the write-back cycle. After the write-back cycle,
it reissues the aborted cycles. This translates into the
following sequence:
Step 1 The processor starts a cacheable burst read
cycle.
Step 2 One clock cycle later, AHOLD is asserted. This
switches the address bus into an input one clock
cycle after AHOLD is asserted.
Step 3 Two clock cycles after AHOLD is asserted, the
EADS and INV signals are asserted to start the
snooping cycle.
Step 4 Two clock cycles after EADS is asserted, HITM
becomes valid. The line is modified, therefore
HITM = 0.
Step 5 Note that the processor-initiated access is not
completed because BLAST = 1.
Step 6 With HITM going Low, the core system logic
asserts BOFF in the next clock cycle to the
snooping processor to reorder the access.
BOFF overrides BRDY. Therefore, the partial
read is not used. It is reread later.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| AM486DX4 | High-Performance, Clock-Selectable, 3.3 V, 32-Bit Microprocessor(3.3V高性能時(shí)鐘可選32位微處理器) |
| AM49DL320BGB701S | 32 Megabit (4 M x 8-Bit/2 M x 16-Bit) CMOS 3.0 Volt-only, Simultaneous Operation Flash Memory and 32 Mbit (2M x 16-Bit) Pseudo Static RAM |
| AM49DL320BGB701T | 32 Megabit (4 M x 8-Bit/2 M x 16-Bit) CMOS 3.0 Volt-only, Simultaneous Operation Flash Memory and 32 Mbit (2M x 16-Bit) Pseudo Static RAM |
| AM49DL320BGB851S | 32 Megabit (4 M x 8-Bit/2 M x 16-Bit) CMOS 3.0 Volt-only, Simultaneous Operation Flash Memory and 32 Mbit (2M x 16-Bit) Pseudo Static RAM |
| AM49DL320BGB851T | 32 Megabit (4 M x 8-Bit/2 M x 16-Bit) CMOS 3.0 Volt-only, Simultaneous Operation Flash Memory and 32 Mbit (2M x 16-Bit) Pseudo Static RAM |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AM486DX2-66V16BGC | 制造商:Advanced Micro Devices 功能描述:MPU AM486 RISC 32-Bit 0.35um 66MHz 5V 168-Pin PGA |
| AM486DX2-66V16BGI | 制造商:Advanced Micro Devices 功能描述:MPU AM486 RISC 32-Bit 0.35um 66MHz 5V 168-Pin PGA |
| AM486DX2-66V16BHI | 制造商:Advanced Micro Devices 功能描述:MPU AM486 RISC 32-Bit 0.35um 66MHz 5V 208-Pin SQFP |
| AM486DX4100C16BGI | 制造商:AMD 功能描述:* |
| AM486DX5-133V16BHC | 制造商:Advanced Micro Devices 功能描述:MPU AM486 RISC 32-Bit 0.35um 133MHz 5V 208-Pin SQFP |
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