Memory Question

One of my routers, a 2521, seems to have 14MB of DRAM, according to the show ver command. It says that there are 14336K. However, it seems very unlikely that there is actually a 14MB stick in there, and more likely that it is 16 but with 2 MB doing something else. I'm thinking it's something like the way Linux machines don't report the space for the kernel in total memory, because it can never be free.

However, both a 2501 and 2514 show 16384K as I would expect.

Is there something different about the 2521?

Also, I thought that this line also showed flash, but apparently it doesn't.

cisco 2500 (68030) processor (revision A) with 16384K/2048K bytes of memory.

I thought that the 2048K was flash, but show flash shows this:

8192K bytes of processor board System flash (Read ONLY)

8 MB of flash?

Can someone clear this up for me?

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Comments

mwgood

Some of the answer is here - http://www.cisco.com/warp/public/130/choosing_ios.shtml#ios

Darthn3ss

^ i didn't look at that but is it possible that you have a 2mb partition?

jvax

Rearden wrote:

One of my routers, a 2521, seems to have 14MB of DRAM, according to the show ver command. It says that there are 14336K. However, it seems very unlikely that there is actually a 14MB stick in there, and more likely that it is 16 but with 2 MB doing something else. I'm thinking it's something like the way Linux machines don't report the space for the kernel in total memory, because it can never be free.

However, both a 2501 and 2514 show 16384K as I would expect.

Is there something different about the 2521?

Also, I thought that this line also showed flash, but apparently it doesn't.

cisco 2500 (68030) processor (revision A) with 16384K/2048K bytes of memory.

I thought that the 2048K was flash, but show flash shows this:

8192K bytes of processor board System flash (Read ONLY)

8 MB of flash?

Can someone clear this up for me?

AFAIK, the 2MB of RAM is onboard. So you have a 14MB RAM stick in your 2521, and 16 RAM sticks in your 2501 and 2514.

In both cases, your routers' total RAM equals or exceeds 16MB so you can use any of the newest IOS images RAM-wise.

Flash-wise, you have only 8MB of flash so you need to upgrade it to 16MB if you want to use newer IOS versions.

Hope this helps.

jvax

Rearden wrote:

Can someone clear this up for me?

If you don't mind getting your hands dirty, try removing the RAM stick and booting from ROM, then check "sh ver".

You need to do a "config-register 0x2101" in global config mode to boot from ROM, otherwise your IOS would not boot properly with insufficient RAM.

Change your config-register back to 0x2102 to boot from flash.

Rearden

I have an extra 16MB stick here. I'll throw it in and see if the reporting is any different.

I don't think it's really a problem as much as I am just curious, although I do wonder what this I/O memory is used for and why it is separate.