Siemens SIMATIC Box PC 820, Руководство пользователя

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2-45
Box PC 820 / PC FI45 V2, Manual
A5E00051531-03
Option “ Memory Cache”
The following pop-up menu appears when you select the option “Memory cache” in
the main menu:
PhoenixBIOS Setup Utility
Item Specific Help
System Time:
F1
ESC
Help
Exit
System Date:
[ 15:35:32 ]
Select Item
Select Menu
+ / –
Enter Select
Change Values
Sub-Menu
F9
F10
Setup Defaults
Save and Exit
Diskette A:
[ 1,44 MB 3
1/
2 “]
Diskette B:
[ Disabled ]
Primary Master
[8455MB]
Primary Slave
[8455MB]
Memory Cache:
Boot Options
Keyboard Features
[Write
Hardware Options
System Memory:
Extended Memory:
Main
Secondary Master
[CD-ROM]
Secondary Slave
[None]
[ 04/05/1999 ]
640 KB
64512 KB
Controls caching of system
conventional memory and
memory above one megabyte
Disabled
Write Through
Write Back
Figure 2-12 Example: “Memory Cache” Submenu
A cache is a fast intermediate memory located between the CPU and the memory
(DRAM). Repeated memory access operations are executed in the fast cache, and
not in the main memory, provided the feature is enabled. It may be necessary to
disable the cache with certain hardware and software because intentional program
runtimes or delay times are prevented by the fast cache.
[Disabled] Cache is disabled.
[Write Through] Write access is only concluded when an entry is made in the main
memory.
[Write Back] Write access is concluded immediately, the entry in the RAM takes
place in the background.
Motherboard
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