466 DX/2  (259-5149)             Cache Memory           Faxback Doc. # 2220

The computer supports 64KB, 128KB, or 256KB of secondary cache memory.

   64K External Cache Part # AXX-7072 has replaced AX259-7230
  128K External Cache Part # AXX-7231 has replaced AX259-7231
  256K External Cache Part # AXX-7071 has replaced AX259-7232

NOTE: The memory kits listed above are orderable from National Parts.

Cache Memory Configurations:

Each secondary cache memory configuration requires one 15ns dirty bit
SRAM, one 15 ns tag SRAM, and four or eight 20 ns data SRAMs. The
following table shows the number and type of SRAMs required for each
configuration:

┌─────────────────────────────────────────────────┐
│SRAM TYPE, LOCATION, AND SIZE                    │
├────────────┬─────────┬───────────┬──────────────┼────────┐
│ DATA:      │ DATA:   │ TAG:      │ DIRTY BIT:   │ TOTAL  │
│ U46-U49    │ U42-U45 │ U50       │ U51          │ CACHE  │
│ (Bank 0)   │         │           │              │ MEMORY │
├────────────┼─────────┼───────────┼──────────────┼────────┤
│ 8KB x 8    │ 8KB x 8 │ 8KB x 8   │ 64KB x 1     │ 64KB   │
├────────────┼─────────┼───────────┼──────────────┼────────┤
│ 32KB x 8   │ ---     │8KB x 8 or │ 64KB x 1     │ 128KB  │
│            │         │32KB x 8   │              │        │
├────────────┼─────────┼───────────┼──────────────┼────────┤
│ 32KB x 8   │ 32KB x 8│ 32KB x 8  │ 64KB x 1     │ 256KB  │
└────────────┴─────────┴───────────┴──────────────┴────────┘
┌─────────────────────────┐
│Main Logic Board Layout: │
└─────────────────────────┘
                         Back of Computer
     ┌─┬───┬─┬──────────┬─┬───┬─┬───┬─┬─┬─┬─┬─────────────────┐
     │ └───┘ └──────────┘ └───┘ └───┘ └─┘ └─┘┌┐               │
     │(123)                                  └┘               │
     │ °°° J31                                    (123)       │
     │ °°° J30                      ┌─┐            °°° J9  ┌─┐│
     │ °°° J29                      │ │            °°° J11 │ ││
     │ °°° J28                      │ │           (123)    ├─┤│
     │ °°° J27                      │ │(321)               │ ││
     │ °°° J26                      │ │ °°° J13            └─┘│
     │ ┌┐┌┐┌┐┌┐┌┐           J32 °   │ │ °°° J14               │
     │ ││││││││││               °   │ │(321)             ┌┐   │
     │ ││└┘└┘└┘└┘                   │ │                  ││┌┐ │
     │ └┘   (97531)                 │ │                  ││││ │
     │       °°°°° J16              │ │<── Riser         ││││ │
     │       °°°°°                  │ │    Card          ││││ │
     │    (10-8642)                 │ │    Connector     ││││ │
     │┌┐┌┐┌┐┌┐┌┐┌┐┌┐┌┐┌┐┌┐          │ │                  ││││ │
     │││││││││││││││││││└┘          │ │                  ││││ │
     │└┘└┘└┘└┘└┘└┘└┘└┘└┘└─ U51      │ │                  └┘└┘ │
     │└──────┘└──────┘└─ U50        │ │                       │
     │ Bank 1  Bank 0               │ │                       │
     │U46-U49  U42-U45              └─┘                       │
     │                                                        │
     │┌────────────────────┐                                  │
     │├────────────────────┤                                  │
     │├────────────────────┤                                  │
     │├────────────────────┤                                  │
     │╞════════════════════╡                                  │
     │├────────────────────┤                                  │
     │├────────────────────┤                                  │
     │├────────────────────┤                                  │
     │└────────────────────┘                                  │
     │┌─────────────────────────────┐                         │
     │└─────────────────────────────┘                         │
     │ °° J20                                                 │
     └────────────────────────────────────────────────────────┘

Secondary Cache Memory (J16):
┌────────────┬───────────────────────────────────────┐
│CACHE SIZE  │ J16 JUMPER SETTINGS                   │
├────────────┼───────────────────────────────────────┤
│None        │ 1-2,3-4,5-6,9-10 (factory settings)   │
│64KB        │ No jumpers installed (remove factory jumpers)
│128KB       │ 1-2,5-6,7-8                           │
│256KB       │ 1-2,3-4,5-6,9-10                      │
└────────────┴───────────────────────────────────────┘

┌──────────────────┐
│Installing SRAMs: │
└──────────────────┘

Before you begin, carefully read the following steps and the cache
memory kit instructions.

Note: Retain the antistatic package the SRAMs are shipped in, in case
      you later remove SRAMs.

To install SRAMs:

1. Turn off the computer, and disconnect all cables.
2. Discharge any accumulated static electricity from your body by
   touching a grounded metal object. Then, open the computer.
3. Remove any expansion adapters installed in the three-slot expansion
   area by removing the expansion slot screws, disconnecting any data
   cables, and gently moving each adapter back and forth while pulling
   it out of the riser card connector.
4. Install each SRAM in the appropriate socket.

   Align the notch on each SRAM with the notch on the socket. Being
   careful not to bend the pins, press down on the SRAM until it is
   fully inserted.

5. Set Jumper block J16 for the new configuration. (See Above Chart)
6. Reinstall any expansion adapters you removed.
7. Be sure the internal cables are securely connected and do not cause
   mechanical interference. Then, close the computer.
8. Reconnect all cables.

Removing SRAMS:

Use a DIP device removal tool to remove SRAMs. Store SRAMs in an
antistatic package. Set Jumper Settings above.