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jcafaro10's avatar
jcafaro10
Aspirant
May 19, 2020

CM600 - slow speeds, is it the modem or Comcast?

Hello all,

 

Just got a CM600 to go with my 200mbps Comcast plan but I'm only seeing speeds around 20mbps.  I've tried contacting them and they've had me power cycle it, replace coax cables, etc but it seems stuck.  They think it could be an issue with the modem.  Is there anyway to tell before I go through trying to return it?  I just found out about my modems status page.  Here's the info from there.  I'm curious about what's going on between channels 15-18.  

 

Startup Procedure
ProcedureStatusComment
Acquire Downstream Channel525000000 HzLocked
Connectivity StateOKOperational
Boot StateOKOperational
SecurityEnableBPI+
IP Provisioning ModeHonor MDDIPv6 only
 
<tabindex=-1>Downstream Bonded Channels</tabindex=-1>
ChannelLock StatusModulationChannel IDFrequencyPowerSNRCorrectablesUncorrectables
1LockedQAM25624525000000 Hz5.6 dBmV40.2 dB00
2LockedQAM25625531000000 Hz5.7 dBmV40.2 dB00
3LockedQAM25626543000000 Hz5.8 dBmV40.2 dB00
4LockedQAM25627549000000 Hz5.8 dBmV40.2 dB00
5LockedQAM25628555000000 Hz6.1 dBmV40.3 dB10
6LockedQAM25629561000000 Hz6.0 dBmV40.0 dB00
7LockedQAM25630567000000 Hz6.0 dBmV40.1 dB00
8LockedQAM25631573000000 Hz6.0 dBmV40.2 dB00
9LockedQAM25632579000000 Hz6.2 dBmV40.3 dB00
10LockedQAM25633585000000 Hz6.4 dBmV40.1 dB00
11LockedQAM25634591000000 Hz6.4 dBmV40.2 dB00
12LockedQAM25635597000000 Hz6.4 dBmV40.2 dB00
13LockedQAM25636603000000 Hz6.4 dBmV39.0 dB30
14LockedQAM25637609000000 Hz6.7 dBmV40.1 dB00
15LockedQAM25638615000000 Hz6.7 dBmV37.2 dB7949739
16Not LockedUnknown00 Hz0.0 dBmV0.0 dB00
17LockedQAM25640627000000 Hz6.7 dBmV23.8 dB795315844
18LockedQAM25641633000000 Hz6.7 dBmV40.1 dB57652
19LockedQAM25642639000000 Hz6.5 dBmV39.9 dB00
20LockedQAM25643645000000 Hz6.5 dBmV39.8 dB00
21LockedQAM25644651000000 Hz6.4 dBmV39.5 dB00
22LockedQAM25645657000000 Hz6.3 dBmV39.5 dB00
23LockedQAM25646663000000 Hz6.4 dBmV39.9 dB00
24LockedQAM25647669000000 Hz6.2 dBmV39.9 dB00
 
<tabindex=-1>Upstream Bonded Channels</tabindex=-1>
ChannelLock StatusUS Channel TypeChannel IDSymbol RateFrequencyPower
1LockedATDMA45120 Ksym/sec36700000 Hz38.8 dBmV
2LockedATDMA15120 Ksym/sec17300000 Hz39.3 dBmV
3LockedATDMA25120 Ksym/sec23700000 Hz39.0 dBmV
4LockedATDMA35120 Ksym/sec30300000 Hz39.0 dBmV
5Not LockedUnknown00 Ksym/sec0 Hz0.0 dBmV
6Not LockedUnknown00 Ksym/sec0 Hz0.0 dBmV
7Not LockedUnknown00 Ksym/sec0 Hz0.0 dBmV
8Not LockedUnknown00 Ksym/sec0 Hz0.0 dBmV

4 Replies

  • plemans's avatar
    plemans
    Guru - Experienced User

    If you have any splitters, attenuators, amplifiers in the line, remove them. 

    Also, check the cable for kinks, damage, bad connectors, corrosion. 

    Another thing you can have them do is try to re-provision the modem. It wouldn't be the first time the wrong provisioning file was sent. 

    If none of that works you've then narrowed the problem to either the line or the modem. 

    You can try exchanging the modem. The cm600 is a pretty solid modem and if you exchanged it, it pretty much points to the line or the provisioning. 

    • jcafaro10's avatar
      jcafaro10
      Aspirant

      Thanks for the response.  I only have one cable line that enters the house and it's not split.  The coax cable connected to it is fairly short and looks fine.

       

      Ive had them reprovision the modem and reset it and that hasn't seemed to work.  I guess I can try exchanging the modem and see if that helps.  The modems run overnight and I see a lot more correctable and uncorrectabkes in these channels, and channel 16 still isn't locked.  

       

      14LockedQAM25637609000000 Hz6.7 dBmV40.1 dB40
      15LockedQAM25638615000000 Hz6.7 dBmV37.7 dB36141285
      16Not LockedUnknown00 Hz0.0 dBmV0.0 dB00
      17LockedQAM25640627000000 Hz6.7 dBmV29.2 dB63118163135
      18LockedQAM25641633000000 Hz6.8 dBmV40.3 dB31401147
      • jcafaro10's avatar
        jcafaro10
        Aspirant

        Hello again,

         

        I went to target and picked up an SB6190 which seemed to completely resolve the problems after activating.  Speeds were up to 200mbps as expected.  After several hours speeds seemed to come back to around 20-50.  I took a look at the status page and noticed something interesting.  While the channels don't entirely line up (and I seem to have some more of them on this modem) it looks like the frequency ranges (615-633mhz) match up between both modems where there's an issue!  I'm guessing that means the issues I'm having are not modem related.  Thoughts?

         

        ChannelLock StatusModulationChannel IDFrequencyPowerSNRCorrectedUncorrectables
        1Locked256QAM16471.00 MHz6.00 dBmV38.98 dB00
        2Locked256QAM17477.00 MHz5.90 dBmV40.37 dB00
        3Locked256QAM18483.00 MHz6.20 dBmV38.98 dB00
        4Locked256QAM19489.00 MHz6.10 dBmV38.98 dB40
        5Locked256QAM20495.00 MHz6.10 dBmV38.98 dB90
        6Locked256QAM21507.00 MHz6.00 dBmV38.61 dB00
        7Locked256QAM22513.00 MHz6.00 dBmV38.98 dB00
        8Locked256QAM23519.00 MHz5.90 dBmV38.98 dB00
        9Locked256QAM24525.00 MHz5.90 dBmV38.61 dB150
        10Locked256QAM25531.00 MHz5.90 dBmV38.98 dB80
        11Locked256QAM26543.00 MHz5.90 dBmV40.37 dB00
        12Locked256QAM27549.00 MHz5.90 dBmV38.98 dB00
        13Locked256QAM28555.00 MHz6.20 dBmV38.98 dB10
        14Locked256QAM29561.00 MHz6.20 dBmV38.98 dB20
        15Locked256QAM30567.00 MHz6.20 dBmV40.37 dB00
        16Locked256QAM31573.00 MHz6.10 dBmV38.98 dB00
        17Locked256QAM32579.00 MHz6.30 dBmV38.98 dB00
        18Locked256QAM33585.00 MHz6.50 dBmV38.98 dB00
        19Locked256QAM34591.00 MHz6.40 dBmV38.98 dB10
        20Locked256QAM35597.00 MHz6.60 dBmV40.37 dB00
        21Locked256QAM36603.00 MHz6.60 dBmV38.61 dB00
        22Locked256QAM37609.00 MHz6.80 dBmV38.98 dB20
        23Locked256QAM38615.00 MHz6.60 dBmV38.61 dB30124
        24Not Locked----39621.00 MHz----------------
        25Not Locked----40627.00 MHz----------------
        26Locked256QAM41633.00 MHz6.90 dBmV37.30 dB6550557591
        27Locked256QAM42639.00 MHz6.70 dBmV38.90 dB00
        28Locked256QAM43645.00 MHz6.70 dBmV39.50 dB10
        29Locked256QAM44651.00 MHz6.40 dBmV39.20 dB20
        30Locked256QAM45657.00 MHz6.40 dBmV39.20 dB00
        31Locked256QAM46663.00 MHz6.40 dBmV39.50 dB20
        32Locked256QAM47669.00 MHz6.40 dBmV39.50 dB20