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THE CS NOTES

Memory Chip Organization and Interleaving

1. Understanding Chip Specifications

  • Format: ⭐$$CapacityOfChip = (\text{Number of Words}) × (\text{Word Size in bits})$$
    • Example: 64K × 1 = 64K words, each word is 1 bit wide → 64K bits total.
    • Example: 512K × 8 = 512K words, each word is 8 bits wide (1 byte) → 512K×8512K times 8 bits total.

2. Converting to Bytes and Bits

  • Bits to Bytes: Divide by 8.
  • Bytes to Bits: Multiply by 8.

3. Calculating Number of Chips Needed
Formula:

$$Number of chips= \frac{\text{Required capacity in bits}}{\text{Capacity per chip in bits}}$$

Example:

  • Required: 512K × 8 bits = 4096K bits.
  • Per chip: 64K × 1 bit = 64K bits.
  • Chips needed= 4096K / 64K = 64

4. Organization for Required Word Width

  • To get 8-bit word width from 1-bit chips, group 8 chips in parallel (same address lines, separate data lines).
  • To get the total memory size, stack enough such groups.

Example for 512K × 8 using 64K × 1 chips:

  • First, 8 chips in parallel → 64K × 8.
  • Required 512K × 8 → 512K / 64K = 8 such groups.
  • Total chips = 8 chips/group×8 groups = 64 chips