Upgrading Simm Dram; Table 3-4 Dram Access Times - Intel i960 Series User Manual

HARDWARE REFERENCE
Frequency Operation
16 MHz Read
20 MHz Read
25 MHz Read
25 MHz Read
33 MHz Read
40 MHz Read
40 MHz Read
16 MHz Write
20 MHz Write
25 MHz Write
25 MHz Write
33 MHz Write
40 MHz Write
40 MHz Write
NOTES:
1. Bandwidths stated are sustained bandwidths, not peak.
2. The extra cycle is the overhead of DRAM precharge. DRAM precharge time only impacts back-to-back cycles.
3.4.2

Upgrading SIMM DRAM

On-board DRAM is located in two SIMM sockets as shown in Figure 3-1 (pg. 3-1). The standard
configuration is 2 Mbytes of memory and may be upgraded to 8 or 32 Mbytes. Table 3-5 shows the
modules which you may use. The memory modules should use 60 or 70 ns Fast Page Mode DRAM
(60 ns memory results in better performance at 25 and 40 MHz operation). Use fast page mode, x32 or
x36, 72 pin SIMMs.
The SIMM block consists of two standard 72-pin SIMM sockets, arranged as two banks. Both SIMM
sockets must contain SIMMs; these cannot be left empty. The sockets accept the following SIMM types.
• 256 Kbyte x 32 = 1 Mbyte
• 256 Kbyte x 36 = 1 Mbyte
The x36 SIMM parity bits are not used in this design. However, the x36 SIMMs are standard for PCs
and workstations, which makes them more readily available. The only penalty is more loading on the
address and control lines due to the extra DRAM devices on the x36 SIMM.
All address and control lines to the SIMMs are terminated with 22 ohm resistors.
3-6
Table 3-4. DRAM Access Times
DRAM Speed Clock Cycles
60, 70ns 3,1,1,1
60, 70ns 3,1,1,1
60ns 3,1,1,1
70ns 4,1,1,1,1
60, 70ns 4,1,1,1,1
60ns 4,1,1,1,1
70ns 5,2,2,2,1
60, 70ns 3,2,2,2
60, 70ns 3,2,2,2
60ns 3,2,2,2
70ns 4,2,2,2,1
60, 70ns 4,2,2,2,1
60ns 4,2,2,2,1
70ns 4,2,2,2,1
• 1 Mbyte x 32 = 4 Mbyte
• 1 Mbyte x 36 = 4 Mbyte
Wait States
1,0,0,0
1,0,0,0
1,0,0,0
2
2,0,0,0
2
2,0,0,0
2
2,0,0,0
2
3,1,1,1
1,1,1,1
1,1,1,1
1,1,1,1
2
2,1,1,1
2
2,1,1,1
2
2,1,1,1
2
2,1,1,1
• 4 Mbyte x 32 = 16 Mbyte
• 4 Mbyte x 36 = 16 Mbyte
Sustained
1
Bandwidth
36 Mbytes/sec
45 Mbytes/sec
66 Mbytes/sec
50 Mbytes/sec
66 Mbytes/sec
80 Mbytes/sec
53 Mbytes/sec
25.6 Mbytes/sec
32 Mbytes/sec
44.5 Mbytes/sec
36 Mbytes/sec
48 Mbytes/sec
58 Mbytes/sec
58 Mbytes/sec