Memory Controller (D0:F0)
8 Memory Controller (D0:F0)
8.1
Functional Overview
8.1.1
DRAM Frequencies and Data Rates
To reduce design complexity and clock network power, the Intel® SCH maintains a
fixed relationship to the FSB clock frequency. The FSB frequency can be 100 MHz or
133 MHz, resulting in support of the following clock frequencies and data rates for
DRAM.
FSB Clock
DRAM Clock
DRAM Data Rate
DRAM Type
Peak Bandwidth
100 MHz
133 MHz
200 MHz
266 MHz
400 MT/s
533 MT/s
DDR2
DDR2
3.2 GB/s
4.2 GB/s
8.1.2
DRAM Command Scheduling
The Intel® SCH memory controller operates at the common core clock, which is one
half the DDR2 memory clock frequency, or ¼ the DDR data rate. To provide efficient
scheduling, the controller is capable of scheduling two operations in the controller core
clock to be able to issue a command every memory clock (where scheduling rules for
the memory devices allow).
The memory controller operates on up to two requests at a time to provide pipelining
for memory commands where possible. It will issue page management commands
(activates and precharges) out of order for the later request, but will always service
reads and writes (CAS operations) in the order in which they were received by the
controller. This provides efficient scheduling while still maintaining in-order rules for
compatibility with the FSB IOQ.
The Intel® SCH never uses any additive latency, which is provided for in DDR2 to
create a posted CAS effect and improve scheduling efficiency in some memory
systems.
8.1.3
Page Management
The memory controller is capable of closing open pages after the pages have been idle
for a configurable period of time. This benefits the system for both power and
performance (when properly configured). From a performance standpoint, it helps
since it can reduce the number of page misses encountered. From a power perspective,
it allows the memory devices to reach the precharge power management state (power
down when all banks are closed), which has better power saving characteristics on
most memory devices than when the pages are left open and the device is in powered
down.
Datasheet
89
INTEL [ INTEL ]
