Product Bulletin - No. 544

Cisco 3600 Series Memory Options and Configuration Guide

Introduction

This Product Bulletin for the Cisco 3600 Series covers the following:

• Processor and memory specifications
  
  
• Platform hardware overview
  
  
• Cisco 3600 Series memory
  
  
• Cisco IOS^® minimum DRAM and Flash memory requirements
  
  
• Factory standard DRAM and Flash memory options
  
  
• Memory rules
  
  
• Main and shared DRAM functionality
  
  
• Network module memory requirements
  
  
• Flash and personal computer memory card international association (PCMCIA) memory options
  
  
• Factors that affect default memory configurations
  
  
• Memory product numbers and APV
  
  

Processor and Memory Specifications

Platform Hardware Overview

Cisco 3660

• 255 Mhz RM5271 RISC processor with 32K internal cache
  
  
• System controller with PCI bus and 4 DMA channels
  
  
• 25Mhz PCI based 6-slot bus
  
  
• 64-bit wide DRAM memory system
  
  
• Two 10ns, 168-pin DIMM slots for up to 256 MB of SDRAM
  
  
• Non-parity and parity SDRAM DIMMS supported
  
  
• Two 80-pin SIMM slots for up to 64 MB of Flash memory
  
  
• Six general purpose PCI bus slots for Network Modules
  
  
• Two PCMCIA slots for additional Flash memory capabilities
  
  
• 115.2 kbps asynchronous support for console and auxiliary ports
  
  
• No xboot functionality. Netbooting not supported in Remote Monitoring (RMON) mode
  
  

Cisco 3640

• 100 Mhz R4700 RISC processor with 32K internal cache
  
  
• System controller with PCI bus and 4 DMA channels
  
  
• 25 Mhz PCI based 4-slot bus
  
  
• 64-bit wide DRAM memory system (configurable for 32 bit also)
  
  
• Four 60ns,72-pin SIMM slots for up to 128 MB of DRAM
  
  
• Non-parity DRAM SIMMS supported
  
  
• Two 80-pin SIMM slots for up to 32 MB of Flash memory
  
  
• Four general purpose PCI bus slots for network modules
  
  
• Two PCMCIA slots for additional Flash memory capabilities
  
  
• 115.2 kbps asynchronous support for console and auxiliary ports
  
  
• No xboot functionality. Netbooting not supported in RMON mode
  
  

Cisco 3620

• 80 Mhz R4700 RISC processor
  
  
• System controller and PCI bus interface
  
  
• 20 Mhz PCI based 2 slot bus
  
  
• 32-bit wide DRAM memory system
  
  
• Four 60ns, 72-pin SIMM slots for up to 64 MB of DRAM
  
  
• Non-parity DRAM SIMMS supported
  
  
• Two 80-pin SIMM slots for up to 32 MB of flash memory
  
  
• Two general purpose PCI bus slots for network modules
  
  
• Two PCMCIA slots for additional Flash memory capabilities
  
  
• 115.2 kbps asynchronous support for console and auxiliary ports
  
  
• No xboot functionality. Netbooting not supported in RMON mode
  
  

The following table list the maximum number of Network Modules that can be configured on a Cisco 3640/3620, and the minimum Cisco IOS version required.

Cisco 3600 Series Memory

The Cisco 3600 Series supports run-from-ram images only. The Cisco 3600 Series routers support the following types of memory:

• Main processor memory—Used to store the running configuration and routing tables. Cisco IOS software is executed from the main memory.
  
  
• Shared (packet) memory—Used for packet buffering by the router's network interfaces.
  
  
• Flash memory—Used to store the IOS^® software image. Can be stored on either the Flash SIMM, or PCMCIA card.
  
  
• Nonvolatile random-access memory (NVRAM)—Used to store the system configuration file and the virtual configuration register.
  
  
• EPROM-based memory—Stores the ROM monitor, that allows booting an operating system software image from Flash or PCMCIA memory when Flash memory does not contain a valid boot helper image.
  
  

Minimum Memory Requirements for DRAM and Flash

Standard Default Factory Options for DRAM and Flash Changes to New System Cisco 3600 Series Default Memory Configuration

As of October 26th, 1998 the Cisco 3600 Series default DRAM memory size has been increased to 32 MB (MEM3600-32D-INCL) replacing the old default of 16 MB. This replaces the existing 16 MB DRAM memory option available on both the Cisco 3640 and Cisco 3620.

The 32 MB DRAM memory default is available on all new system orders placed after October 26th, 1998 on the following feature sets including: 11.1A, 11.2P, 11.3, 11.3T, 12.0, and 12.0T. There will be no additional charge for this memory increase. The Cisco 3600 Series minimum DRAM memory requirement of 24 MB for the IP and IP/IPX/AT/DEC feature sets is still valid for customers who are upgrading to 12.0(1) or 12.0(1)T, and who currently run with 16 or 20 MB of DRAM memory. There are no changes to the Cisco 3600 Series Flash memory default, currently set at 4 MB.

The new DRAM product numbers will include:

• Cisco 3630 (DRAM)
  
  
• • MEM3620-32U48D
    
    
  • MEM3620-32U48D
    
    
  • MEM3620-32U64D
    
    
• Cisco 3640 (DRAM)
  
  
• • MEM3640-32U48D
    
    
  • MEM3640-32U64D
    
    
  • MEM3640-32U128D
    
    
• Cisco 3660 (SDRAM)
  
  
• • MEM3660-32D
    
    
  • MEM3660-64D
    
    
  • MEM3660-128D
    
    

The obsoleted DRAM product numbers for the Cisco 3620 will include:

• MEM3620-16U24D
  
  
• MEM3620-16U32D
  
  
• MEM3620-16U48D
  
  
• MEM3620-16U64D
  
  

The following include the only memory options that are orderable from the factory. If additional memory is required because of the network module configuration, or IOS image size, then only the below configurations are available. Customers may choose to purchase additional memory elsewhere in order to obtain non-standard, and in some cases non-64-bit wide memory configurations.

Memory options orderable from factory for the Cisco 3640:

• MEM3640-16U24D
  
  
• MEM3640-16U32D
  
  
• MEM3640-16U48D
  
  
• MEM3640-16U64D
  
  
• MEM3640-16U128D
  
  

Memory options orderable from factory for the Cisco 3660:

• MEM3660-32U64D
  
  
• MEM3660-32U96D
  
  
• MEM3660-32U128D
  
  
• MEM3660-32U256D
  
  

Memory Rules

The Cisco 3620, Cisco 3640 and Cisco 3660 have different memory options and product numbers due to the difference in memory architectures. The Cisco 3640 can support industry standard dual-bank 8 and 32 MB SIMMs, because of it's 64-bit memory architecture. The Cisco 3620, with a 32-bit architecture, cannot use dual-bank SIMMs, but instead uses a custom Cisco 8 MB single-bank SIMM. It cannot be mixed with the dual-bank 8 MB SIMMs. Both the Cisco 3620 and Cisco 3640 use the same 4 MB and 16 MB SIMMs, but have different product numbers. By default, the 3640 and 3620 ship with non-parity DRAM SIMMS, but parity SIMMs are supported if all banks contain SIMMs that have parity enabled. If parity SIMMs are mixed in a system with non-parity SIMMs the parity function is not supported on any of the SIMMs. Only certain combinations of DRAM SIMMS are permitted. These combinations are shown in Table 6 for the Cisco 3660, in Table 7 for the Cisco 3640 and in Table 8 for the Cisco 3620.

General Guidelines

• The sum of memory in slots 0 and 1 must be a power of 2 in order to stuff slots 2 and 3.
  
  
• Largest memory sizes must always be first.
  
  
• No holes. An unoccupied slot cannot be followed by an occupied one.
  
  
• ROM monitor will display a warning message if illegal SIMM placement or sizing has occurred.
  
  

For the Cisco 3660 the following SDRAM rule apply:

For 64-bit mode operation on the Cisco 3640 the following DRAM rules apply:

For the Cisco 3620 the following rules apply:

Main and Shared DRAM Memory Functionality

The Cisco 3660, Cisco 3640 and Cisco 3620 platforms are partitioned into main processor memory (pmem), and shared packet memory (I/O memory) area's. The IOS software is capable of making a distinction between the two with a finer granularity then if there were hardware distinctions between the two. For example, with 16 MB DRAM configurations, the memory is split by default into 12MB for pmem and 4MB for I/O memory. This 75/25 split occurs upon system initialization, and allows enough packet memory to bring up the most common interface combinations regardless of the total amount of DRAM present in the Cisco 3640/3620 and SDRAM in the Cisco 3660.

In addition, user's have the ability to choose from several options to change this split when required. The new IOS command memory-size (I/O memory) percentage allows DRAM split increases of 30, 40 and 50 perent depending on the type and number of network modules configured.

The Cisco IOS supports an auto-adjusting feature upon startup in which if the I/O memory-percentage has been configured too high; leaving insufficient pmem available for bringing up the IOS image, then the IOS automatically reduces the percentage to a lower value. If the default is not sufficient for an image to boot up, then the user does not have enough DRAM/SDRAM for that particular subset image, and the router will complain in the same manner as existing Cisco platforms that encounter insufficient processor memory.

Main and packet DRAM/SDRAM cannot share or borrow from the other as on the 25xx series routers. If the main DRAM/SDRAM memory is insufficient then either an increase in memory is required; or if the memory size had be adjusted via the IOS, then it would require a decrease.

At least 2 MB of free processor memory and 1.2 MB of free I/O memory is required for most average size networks. You can use the Cisco IOS command show memory free to view the amount of used and available system memory.

Network Modules Memory Requirements

The amount of packet memory required is dependent on the number and types of Network Modules configured, but is also dependent on the amount of memory the Cisco IOS uses for each specific feature. For example, additional processor and packet memory is used when a CT1 or CE1 is configured for Integrated Services Digital Network (ISDN). When the CT1 or CE1 network modules are used in channelized mode much less memory is required. See Table 15 below.

For two or more T1/E1 PRIs, or 12 or more basic rate interfaces (BRIs) configured, Cisco recommends a 60/40 memory split. At this time, the Cisco 3600 Series is shipped with a default memory split of 75/25, so the user will have to reconfigure with the Cisco IOS command memory-size I/O memory 40, or they may receive a SYS-2 MALLOCFAIL error message. This error message occurs when less then 1.2 MB of free I/O memory is available for system use. Increasing the I/O memory size will eliminate this error message.

Table 15 shows the total amounts of memory required, which is a combination of processor and packet memory. The CT1 and CE1 numbers are based on memory required when ISDN Primary-group timeslots have been configured.

As a basic rule of thumb the required DRAM memory for a 60/40 split of each T1/primary rate interface (PRI) can be calculated by assuming that each module requires 4.5 MB of memory, and the E1/PRI requires 6 MB of memory. If the total number is above a factory orderable size then the next available orderable size is recommended.

Flash and PCMCIA Memory Options

Flash SIMM

The Cisco 3600 Series routers contain two Flash memory SIMM sockets for storing the Cisco IOS software image. These SIMMs are not interchangeable with the DRAM SIMMs in the Cisco 3640/3620 and the SDRAM DIMMs in the Cisco 3660. The Flash memory can be upgraded by replacing the existing SIMM with and 8 or 16 MB SIMM, or by adding an additional SIMM to the 2nd Flash memory socket. Unequal value SIMMs are supported by Flash. You must always have at least 1 Flash SIMM installed in the router for normal operations. Partitioning of the Flash memory (Dual Bank Flash [DBF]) is supported if the router is configured for at least 8MB of memory.

Flash PCMCIA

The Cisco IOS software image can also be stored on a PCMCIA Flash card on either of the 2 available PCMCIA slots provided on the Cisco 3660, Cisco 3640 and Cisco 3620. Partitioning is also supported on the PCMCIA cards that support 8 MB or more capacity.

Factors that Affect Default Memory Configurations

The size of the Network routing tables and access lists have the greatest impact on the amount of DRAM required. Only the main processor memory is affected, not the I/O memory, by the size of the routing tables. Increasing the I/O memory only affects the Network Modules packet buffers. In an ideal situation, 16 MB of DRAM with the default memory split, can support up to 10,000 IP and 9,000 IPX routes in the routing tables.

The use of multiple high density Network Modules, such as T1/E1 or MBRI, will require additional packet be configured using the Cisco IOS command memory-size I/O memory command. A 60/40 split is recommend in most situations where more then 2 T1/E1 PRI's or 3 NP-8B's are configured, but 50/50 will also work if network routing tables will allow. The router error message SYS-2-MALLOCFAIL is an indication that insufficient I/O memory is available for the Network Modules configured. This error occurs when less then 1.2 MB of free I/O memory is available to the system. See the preceding Network Module Memory Requirements table for specific amount of memory required.

Memory Product Numbers

Cisco has changed the way that memory upgrades are packaged for the Cisco 3640. This new packaging will reduce customer failures by making it impossible to order invalid memory configurations.