Cisco 3600 Series Multiservice Platforms

How to Determine the SIMM Configuration of a Cisco 3620 or 3640 Series Router

Document ID: 28370

Updated: Jul 07, 2005



When deciding whether to upgrade the memory on the box, it is necessary to determine the exact mix of memory currently installed. This document provides instructions to help you determine the DRAM SIMM configuration of a 3620 or 3640 router. These instructions do not apply to a 2600 or 3660.

Note: On a 2691, 3631, 3725, or 3745, issue the Cisco IOS® software show platform command to see the memory layout.



There are no specific requirements for this document.

Components Used

This document is only applicable to the Cisco 3620 and 3640 Series router.


Refer to Cisco Technical Tips Conventions for more information on document conventions.

Background Information

Cisco 3620 and Cisco 3640 (including 3640A) routers each contain four single in-line memory module (SIMM) sockets for Dynamic RAM (DRAM): bank 0 (SIMM 0), bank 1 (SIMM 1), bank 2 (SIMM 2), and bank 3 (SIMM 3). A socket corresponds to one bank of memory. Each socket can hold one DRAM SIMM of any size permitted for that router.

The 3620 and 3640 series routers have requirements and guidelines for memory. For more information on such guidelines, refer to the Memory Rules section in the document Product Bulletin - No. 544: Cisco 3600 Series Memory Options and Configuration Guide.


Complete these steps:

  1. Log into the router in enable mode:

  2. Issue the Cisco IOS software show version command to find the ROMMON version.

    Router#show version
    Cisco Internetwork Operating System Software
    IOS (tm) 3600 Software (C3640-JSX-M), Version 12.2(19), RELEASE SOFTWARE (fc3)
    Copyright (c) 1986-1999 by cisco Systems, Inc.
    Compiled Tue 30-Nov-99 05:39 by kpma
    Image text-base: 0x60008930, data-base: 0x614B2000
    ROM: System Bootstrap, Version 11.1(20)AA2, EARLY DEPLOYMENT RELEASE 
    Router uptime is 22 weeks, 2 days, 8 hours, 31 minutes
       System restarted by power-on
       System image file is "flash:c3640-jsx-mz.122-19.bin"
    !--- Output suppressed

    Note that in this output, the ROMMON version is 11.1(20)AA2.

  3. Use the ROMMON version to find the address of "dram_config" from this table:

    3620/3640 DRAM Config Addresses

    ROMMON Version Address of dram_config
    11.1(7)AX 0xa0002d18
    11.1(17)AA 0xa0002d18
    11.1(19)AA 0xa0002d18
    11.1(20)AA1 0xa0002d18
    11.1(20)AA2 0xa0002d28
    12.1(17r) 0xa0002cb8

    In this example, the address of dram_config corresponding to ROMMON version 11.1(20)AA2 is 0xa0002d28.

  4. Issue the Cisco IOS software show memory <dram_config address> command to show the value of "dram_config":

    Use the dram_config address from step 3 in the show memory command. For example:

    Router#show memory 0xa0002d28
    A0002D20:                   30000044 04000000          0..D....
    A0002D30: 0000001E 00000000 00000000 00000000  ................
    A0002D40: A0002D50 00000000 00000000 00000000   .-P............
    A0002D50: BFC04D60 80005B40 00000007 00000007  ?@M`..[@........
    A0002D60: 80005D50 00000008 00000003 00000001  ..]P............
    !--- Output suppressed

    Make a note of the first number in the first line of the output. In this example, it is 30000044.

    Tip: You can type an ending memory address slightly higher than the starting one in order to get just the first couple of lines, instead of the entire memory dump. In this specific case, you can type: show memory 0xa0002d28 0xa0002d30.

  5. Enter the first number here.

    Enter the first number from the show memory listing, then press the Tab key on your keyboard.

    Note: Do not use the Enter key.

  6. The memory configuration for your 3620 or 3640 router will be shown in this table:

    SIMM Slot SIMM Size
    Total Memory  

Related Information

Updated: Jul 07, 2005
Document ID: 28370