Cisco 3640 and wic-1adsl speed problems

I recently decided to plug my wic-1adsl card into a 3640 router because my 2620 had a power supply failure. I noticed that the cisco 3640 ran very slow, and speed tests topped out at 2.6mbps downlink speeds. For a while I couldn’t figure out why a router that is faster with more memory would run slower than my 2620 router. I later discovered the reason for the slowness was because of a bandwidth limit on the nm-1fe1r2w card I was using to give me wic slots.

sh controller atm0/0

you will see
DSCC4 Clockrates:
DSCC0 = 2600000 (ATM0/0)
DSCC1 = 1000000 (ATM0/0)

Now This is why I am only getting about 2.5mbps download.

If you change the setting ie:

int atm0/0 clockrate aal5 5300000

then do a

show controller atm0/0
you get :

DSCC4 Clockrates:
DSCC0 = 5300000 (ATM0/0)
DSCC1 = 1000000 (ATM0/0)
Now my speed tests are topping out at about 5.2mbps and change.

Now here is the interesting part. On the 3640 53000 is as high as I can go, while on my 2620 the output is as follows.
cisco 2620 (output of sh controller atm0/0)
DSCC4 Clockrates:
DSCC0 = 8000000 (ATM0/0)
DSCC1 = 8000000 (ATM0/0)

 

My guess is that each nm card reserves a certain amount of bandwidth for the interfaces on each card. The card I was using had 1 fe port 1 tokenring port and 2 wic slots, my guess is that those other interfaces used or reserved some of the total bandwidth for the connection. I am thinking that a nm-2w card might solve the problem, however I have not yet tested this theory.

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