Side-Port Memory Interface
© 2009 Advanced Micro Devices, Inc.
45732 AMD 780E Databook 3.10
Proprietary
2-3
Figure 2-3 RS780E Host Bus Interface Signals
2.2
Side-Port Memory Interface
In order to significantly decrease system power and increase graphics performance, the RS780E provides an optional
side-port memory interface for dedicated frame buffer memory, to be used exclusively for the integrated graphics core.
The side-port memory interface can significantly reduce system power by allowing the CPU to stay in its lowest power
state during periods of inactivity. Screen refreshes are fetched from the side-port memory, and there is no need to "wake
up" the CPU to fetch screen refresh data.
The RS780E memory controller is unique and highly optimized. It operates in 16-bit mode at very high speed (up to
DDR2-800 and DDR3-800, and up to DDR3-1200 when the core voltage is fixed at 1.1V), and has a programmable
interleaved mode that significantly increases the memory bandwidth and reduces data latency to the integrated graphics
core. The additional bandwidth provided to the internal graphics core will also aid the RS780E in reaching and exceeding
Microsoft's Windows Vista
®
Premium logo requirements.
2.2.1 DDR2 Memory Interface
Figure 2-4, “RS780E Side-Port Memory Interface,” on page 2-4
illustrates the side-port memory interface of the
RS780E.
The RS780E memory controller supports up to 128MB of dedicated side-port frame buffer DDR2 memory. It controls a
single rank of DDR2 devices in 16-bit memory configuration. It supports device sizes of 256, 512, and 1024 Mbits, and a
device width of x16. Because the memory controller supplies only one chip select signal, only devices with one chip
select are supported. A wide range of DDR2 timing parameters, configurations, and loadings are programmable via the
RS780E memory controller configuration registers
HT_RXCADN
2
2
RS78
0E
CPU
HT_TXCALP
HT_RXCALN
HT_RXCALP
HT_TXCALN
HT_RXCADP
HT_RXCTLN
HT_RXCTLP
HT_RXCLKN
HT_RXCLKP
16
16
HT_TXCADN
2
2
HT_TXCADP
HT_TXCTLN
HT_TXCTLP
HT_TXCLKN
HT_TXCLKP
16
16
2
2
2
2