Windows 10, LAN on MB (10/100/1000). MoCA filter and splitter where cable enters house - one leg to video distribution box, second leg directly to my modem. Had 200 MB plan and was getting around 180 MB. Upgraded plan to 1200 MB and modem (Arris SB8200, DOCSIS 3.1), Cat 6 directly from desktop directly to modem port just to test - would "spike" speed to around 700 MB then immediately throttle down to 320 MB - 380 MB. Reset and reprovisioned modem twice. No change. Had Comcast Tech out who checked speed at pole (1200 MB), speed at tap for house (1200 MB), speed at modem (1200 MB) with "excellent power levels" per Xfinity Tech. Add SB8200 in the mix and speed drops to 320-380 MB. Tech said "Speeds based on our equipment. SB8200 might not hold full boot file. Try our Xfi modem." Did that - same speeds. Would spike to around 600 MB then drop back to 320-380 MB. Hmmm, ok. Try another gig speed modem. Got a Netgear CM1200 yesterday. Set up with Cat 6 direct from desktop to modem. Testing wee hours of the AM and get a little better but not much - certainly not 1 GB.
Using speedtest.net app in W10 rather than browser test - Browser test is consistently 50-100 MB slower. Modem reports:
Startup Procedure
Procedure
Status
Comment
Acquire Downstream Channel
627000000 Hz
Locked
Connectivity State
OK
Operational
Boot State
OK
Operational
Security
Enabled
BPI+
IP Provisioning Mode
Honor MDD
honorMdd(4)
Downstream Bonded Channels
Channel
Lock Status
Modulation
Channel ID
Frequency
Power
SNR
Correctables
Uncorrectables
1
Locked
QAM256
32
627000000 Hz
7.8 dBmV
41.2 dB
0
0
2
Locked
QAM256
1
435000000 Hz
6.3 dBmV
40.6 dB
0
0
3
Locked
QAM256
2
441000000 Hz
6.1 dBmV
40.5 dB
0
0
4
Locked
QAM256
3
447000000 Hz
6.3 dBmV
40.5 dB
0
0
5
Locked
QAM256
4
453000000 Hz
5.9 dBmV
40.5 dB
0
0
6
Locked
QAM256
5
459000000 Hz
5.8 dBmV
40.5 dB
0
0
7
Locked
QAM256
6
465000000 Hz
5.4 dBmV
40.4 dB
0
0
8
Locked
QAM256
7
471000000 Hz
5.5 dBmV
40.4 dB
0
0
9
Locked
QAM256
8
477000000 Hz
5.5 dBmV
40.4 dB
0
0
10
Locked
QAM256
9
483000000 Hz
5.8 dBmV
40.5 dB
0
0
11
Locked
QAM256
10
489000000 Hz
6.1 dBmV
40.5 dB
0
0
12
Locked
QAM256
11
495000000 Hz
6.4 dBmV
40.4 dB
0
0
13
Locked
QAM256
12
507000000 Hz
6.7 dBmV
40.5 dB
0
0
14
Locked
QAM256
13
513000000 Hz
6.8 dBmV
40.6 dB
0
0
15
Locked
QAM256
14
519000000 Hz
6.3 dBmV
40.6 dB
0
0
16
Locked
QAM256
15
525000000 Hz
6.6 dBmV
40.8 dB
0
0
17
Locked
QAM256
16
531000000 Hz
6.1 dBmV
40.8 dB
0
0
18
Locked
QAM256
18
543000000 Hz
6.1 dBmV
40.7 dB
0
0
19
Locked
QAM256
19
549000000 Hz
6.1 dBmV
40.7 dB
0
0
20
Locked
QAM256
20
555000000 Hz
6.7 dBmV
40.9 dB
0
0
21
Locked
QAM256
21
561000000 Hz
7.1 dBmV
40.9 dB
0
0
22
Locked
QAM256
22
567000000 Hz
7.4 dBmV
41.1 dB
0
0
23
Locked
QAM256
23
573000000 Hz
7.4 dBmV
40.9 dB
0
0
24
Locked
QAM256
24
579000000 Hz
7 dBmV
40.9 dB
0
0
25
Locked
QAM256
25
585000000 Hz
6.8 dBmV
40.8 dB
0
0
26
Locked
QAM256
26
591000000 Hz
6.5 dBmV
41 dB
0
0
27
Locked
QAM256
27
597000000 Hz
6.1 dBmV
41.1 dB
0
0
28
Locked
QAM256
28
603000000 Hz
6.9 dBmV
41.2 dB
0
0
29
Locked
QAM256
29
609000000 Hz
5.8 dBmV
41 dB
0
0
30
Locked
QAM256
30
615000000 Hz
7 dBmV
41 dB
0
0
31
Locked
QAM256
31
621000000 Hz
6.7 dBmV
41 dB
0
0
32
Not Locked
Unknown
0
0 Hz
0.0 dBmV
0.0 dB
0
0
Upstream Bonded Channels
Channel
Lock Status
US Channel Type
Channel ID
Symbol Rate
Frequency
Power
1
Locked
ATDMA
1
5120 Ksym/sec
35600000 Hz
43.5 dBmV
2
Locked
ATDMA
2
5120 Ksym/sec
29200000 Hz
44 dBmV
3
Locked
ATDMA
3
5120 Ksym/sec
22800000 Hz
44 dBmV
4
Locked
ATDMA
4
5120 Ksym/sec
16400000 Hz
44 dBmV
5
Not Locked
Unknown
0
0 Ksym/sec
0 Hz
0.0 dBmV
6
Not Locked
Unknown
0
0 Ksym/sec
0 Hz
0.0 dBmV
7
Not Locked
Unknown
0
0 Ksym/sec
0 Hz
0.0 dBmV
8
Not Locked
Unknown
0
0 Ksym/sec
0 Hz
0.0 dBmV
Downstream OFDM Channels
Channel
Lock Status
Modulation / Profile ID
Channel ID
Frequency
Power
SNR / MER
Active Subcarrier Number Range
Unerrored Codewords
Correctable Codewords
Uncorrectable Codewords
1
Locked
0 ,1 ,2 ,3
33
678000000 Hz
7.7 dBmV
40.6 dB
1108 ~ 2987
107783651
105295721
0
2
Not Locked
0
0
0 Hz
0 dBmV
0.0 dB
0 ~ 4095
0
0
0
Upstream OFDMA Channels
Channel
Lock Status
Modulation / Profile ID
Channel ID
Frequency
Power
1
Not Locked
0
0
0 Hz
0 dBmV
2
Not Locked
0
0
0 Hz
0 dBmV
Extended Upstream Transmit Power
Enable Extended Upstream Transmit Power
Current System Time:Sun Mar 28 06:41:00 2021
System Up Time:13:47:03
I'm at a loss to explain why I'm not getting the plan's reported speed. I think I've isolated just about everything on the system except changing out LAN card in desktop but I'm thinking that's not it since I was briefly seeing 700-800MB before it dropped back down to 320-380MB. Coax cable from tap on line to modem - check (good - no interference, no power drop, per Xfinity Tech). Cat 6 - check (good, tried two different ones). Modem - Check (three different modems, three different manufacturers). Power levels in spec - check (Xfinity Tech confirmed).
I'm at a loss to figure this out. Hopefully someone will have an idea.
Frankenstein home built. Box is ATX form factor from early 2000's that over the years has been upgraded with new power supply(s), motherboards and chips. Current MB and chip are probably 5 years old
I’ll tell you something I sometimes do to help diagnose a particular difficult problem, it’s a little unconventional probably to most folks standards, anyway I have a ubuntu Linux install disk on a flash drive, so I boot this up, it boots up into memory, it gives a very nice functional desktop, no configuration needed in most cases, so your even online with your Ethernet port, so it gives the option to install or just try out, choose try out, so it already has Firefox installed, so I just navigate to my favorite speed test site, so this eliminates the windows operating system, different drivers etc, so I run a speed test and compare the results of the two, so in my case, with the 2.5 gig adapter I was originally getting slow speeds with win 10, with the Linux I was getting the 1400 - 1500 I posted before, the exact same hardware setup, so that immediately ruled out my Comcast connection, modem and all my hardware I was using, so that told me it had something to do with win 10 I was using, but if you get the same speeds its probably a hardware issue, a simple test, but tells you what you need to know
BRAVO to jlavaseur for the suggestion on Unbuntu as a diagnostic tool! Dowloaded, booted to Unbuntu and tested again, both going through router (Netgear R6700v3) and direct to modem. Here's the results:
This is with the Motorola MB8611. Clearly using Unbuntu and bypassing all the Windows 10 stuff (whatever that may be) get results close to 1GB. Not quite there but I'd be happy to consistently get 800-850 Mbps down and 40 Mbps up in Windows 10. At this point, not sure what else to sniff out in Windows to see if there's any way to match the Unbuntu speeds. Open to suggestions.
I have same issue with CM1200 Netgear. I have had techs reset modem, factory rest. A tech came in an also installed an Xfinity modem but speeds at pc were less than my CM1200. The tech was able to get 1200mbs on pole and at cable to modem. But those speeds could not be replicated on a pc, laptop, playstation by means of wifi or wired. My fluxuation in speeds changed 200mbs on testing but not over 500 at most. Any idea how to fix this? I upgraded from 200mb to 1200mb and nowhere near that speed.
Hello, @user_8d300d. I see you are still seeing speed fluctuations even after a tech visit. We definitely want to get this sorted out. I ask that you reach out privately, so we can cover the details of your account. You can start by clicking the chat icon located in the top right corner on your forums page when signed in. Once there, you can search for "Xfinity Support" to compose your direct message. Please add your first and last name to help us locate your account. Let me know if you have any questions.
I am an Official Xfinity Employee. Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership. We ask that you post publicly so people with similar questions may benefit from the conversation. Was your question answered? Please, mark a reply as the Accepted Answer.
brintonh
Contributor
•
33 Messages
4 years ago
@EG I see that you've been helpful to others with modem issues. Can you take a look at this thread and give me your thoughts?
0
0
Jlavaseur
Problem Solver
•
948 Messages
4 years ago
@brintonh is your computer any chance a Dell?
0
0
brintonh
Contributor
•
33 Messages
4 years ago
Frankenstein home built. Box is ATX form factor from early 2000's that over the years has been upgraded with new power supply(s), motherboards and chips. Current MB and chip are probably 5 years old
0
0
Jlavaseur
Problem Solver
•
948 Messages
4 years ago
I’ll tell you something I sometimes do to help diagnose a particular difficult problem, it’s a little unconventional probably to most folks standards, anyway I have a ubuntu Linux install disk on a flash drive, so I boot this up, it boots up into memory, it gives a very nice functional desktop, no configuration needed in most cases, so your even online with your Ethernet port, so it gives the option to install or just try out, choose try out, so it already has Firefox installed, so I just navigate to my favorite speed test site, so this eliminates the windows operating system, different drivers etc, so I run a speed test and compare the results of the two, so in my case, with the 2.5 gig adapter I was originally getting slow speeds with win 10, with the Linux I was getting the 1400 - 1500 I posted before, the exact same hardware setup, so that immediately ruled out my Comcast connection, modem and all my hardware I was using, so that told me it had something to do with win 10 I was using, but if you get the same speeds its probably a hardware issue, a simple test, but tells you what you need to know
0
0
brintonh
Contributor
•
33 Messages
4 years ago
BRAVO to jlavaseur for the suggestion on Unbuntu as a diagnostic tool! Dowloaded, booted to Unbuntu and tested again, both going through router (Netgear R6700v3) and direct to modem. Here's the results:
This is with the Motorola MB8611. Clearly using Unbuntu and bypassing all the Windows 10 stuff (whatever that may be) get results close to 1GB. Not quite there but I'd be happy to consistently get 800-850 Mbps down and 40 Mbps up in Windows 10. At this point, not sure what else to sniff out in Windows to see if there's any way to match the Unbuntu speeds. Open to suggestions.
0
0
user_8d300d
Visitor
•
1 Message
4 years ago
I have same issue with CM1200 Netgear. I have had techs reset modem, factory rest. A tech came in an also installed an Xfinity modem but speeds at pc were less than my CM1200. The tech was able to get 1200mbs on pole and at cable to modem. But those speeds could not be replicated on a pc, laptop, playstation by means of wifi or wired. My fluxuation in speeds changed 200mbs on testing but not over 500 at most. Any idea how to fix this? I upgraded from 200mb to 1200mb and nowhere near that speed.
1
0