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Integrated Functions (Continued)

4.3.5

Address Translation

The memory controller supports two address translations

depending on the method used to interleave pages. The

hardware automatically enables high order interleaving.

Low order interleaving is automatically enabled only under

specific memory configurations.

4.3.5.1

High Order Interleaving

High Order Interleaving (HOI) uses the most significant

address bits to select which bank the page is located in.

This interleaving scheme works with any mixture of DIMM

types. However, it spreads the pages over wide address

ranges. For example, two 8 MB DIMMs contain a total of

four component pages. Two pages are together in one

DIMM separated from the other two pages by 8 MB.

4.3.5.2

Auto Low Order Interleaving

The memory controller requires that banks [0:1] if both

installed, be identical and banks [2:3] if both installed, be

identical. When banks [0:1] are installed or banks [2:3] are

installed Auto Low Order Interleaving (LOI) is in effect for

those bank pairs. Therefore each DIMM (banks [0:1] or[

:[2,3) must have the same number of DIMM banks, compo-

nent banks, module sizes and page sizes.

LOI uses the least significant bits after the page bits to

select which bank the page is located in. This requires that

memory is a power of 2, that the number of banks is a

power of 2, and that the page sizes are the same. As stated

before, for LOI to work, the DIMMs have to be of the same

type. LOI does give a good benefit by providing a moving

page throughout memory. Using the same example as

above, two banks would be on one DIMM and the next two

banks would be on the second DIMM, but they would be

linear in address space. For an eight bank system that has

1 KB address (8 KB data) pages, there would be an effec-

tive moving page of 64 KB of data.

4.3.5.3

Physical Address to DRAM Address

Conversion

Tables 4-16 and 4-17 give Auto LOI address conversion

examples when two DIMMs of the same size are used in a

system. Table 4-16 shows a one DIMM bank conversion

example, while Table 4-17 shows a two DIMM bank exam-

ple.

Tables 4-18 and 4-19 give Non-Auto LOI address conver-

sion examples when either one or two DIMMs of different

sizes are used in a system. Table 4-18 shows a one DIMM

bank address conversion example, while Table 4-19 shows

a two DIMM bank example. The addresses are computed

on a per DIMM basis.

Since the DRAM interface is 64 bits wide, the lower three

bits of the physical address get mapped onto the DQM[7:0]

lines. Thus, the address conversion tables (Tables 4-16

through 4-19) show the physical address starting from A3.

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