Siemens SIMATIC PC 670, Equipment Manual

Page: 97 / 200

Configuring the Computing Unit in BIOS Setup
Release 04/02
5-9
Panel PC 670 Computing Unit, Equipment Manual
”Memory Cache” Submenu
The following pop-up menu appears when you select the submenu “Memory
cache” in the main menu:
PhoenixBIOS Setup Utility
Item Specific Help
System Time:
ESC Exit
System Date:
Select Item
Select Menu
+ / –
Select
Change Values
Sub-Menu
F9
F10 Setup Defaults
Save and Exit
Diskette A: [1.44 MB, 31/2” ]
Primary Master [20496 MB]
Primary Slave [None]
Memory Cache:
Boot Options
Keyboard Features
Hardware Options
System Memory:
Extended Memory:
Secondary Master [CD–ROM]
Secondary Slave [None]
[ 03/12/2002 ]
640 KB
121856 MB
Enter
Help
F1
Main
[ 15 :35:32 ]
[Write Back]
Disabled
Write Through
Write Back
Controls caching of
system conventional
memory and memory
above one megabyte.
Figure 5-4 “Memory Cache” Field
A cache is a fast memory buffer between the CPU and main memory (DRAM).
Recurrent memory access operations are executed in the fast cache, instead of
the main memory, if the function is enabled. In rare instances involving some
hardware and software combinations, it may be necessary to disable the cache
because the program runtimes or waits are too short on account of the fast cache.
[Disabled] Cache is disabled
[Write Through] Write access is not concluded until the entry has been made in main
memory
[Write Back] Write access is concluded immediately; the entry in main memory
takes place in the backround (default)