
128
PRELIMINARY
82453KX/GX, 82452KX/GX, 82451KX/GX (MC)
A
Figure 3. MIC to Memory Interconnections
3.3.1.2 4-Way DRAM Configuration (450GX Only)
MIC
I0D[17:0]
I1D[17:0]
I2D[17:0]
I3D[17:0]
I0D[35:18]
I1D[35:18]
I2D[35:18]
I3D[35:18]
I0D[53:36]
I1D[53:36]
I2D[53:36]
I3D[53:36]
I0D[71:54]
I1D[71:54]
I2D[71:54]
I3D[71:54]
MDE[17:0]
MDE[35:18]
MDE[53:36]
MDE[71:54]
MICCMD[6:0]#
I0D[71:0] = Interleave 0 Data Bus.
I1D[71:0] = Interleave 1 Data Bus.
I2D[71:0] = Interleave 2 Data Bus.
I3D[71:0] = Interleave 3 Data Bus.
MICs
In the 4-way interleaved DRAM configuration, the memory controller supports up to 8 rows of conventional
DRAM. Each of these rows can be up to 512 Mbytes, using 64-Mbit technology. This configuration is illustrated
in Figure 4, as implemented with DSSIMMs.
The basic structure of the 4-way interleaved memory (Figure 4) is four 72-bit word wide connections from the
DRAM time multiplexed to the MC. This multiplexing allows the MC to read or write memory at the rate of one
72-bit word each clock cycle and to hide much of the access latency of the DRAM devices.
Logically, the 4-way configuration requires eight RAS# lines and eight CAS# lines (one for each row). The
RAS# signals latch the row address in the four interleaves, and the CAS# signals latch the column address in
each interleave. MA[12:0] and WE# are broadcast to all devices, and must be buffered to each DSSIMM. The
exact buffer type used is system design dependent.
The minimum memory size for this configuration is 4 Mbytes using 4-Mbit technology organized as 512kx8
devices (1 row, 4 Mbytes, operating as non-interleaved). The maximum size is 4 Gbytes using 64-Mbit
technology. Mixing of row sizes is supported; however, within a row, all SIMMs must be the same size.