5 Messages
Not Reaching 2000 Mbps / 300 Mbps up MT8733 SYNC Timing and UCD Invalid
Just had customer service put in order for upgrade to 2gbps last night, planned maintenance was overnight, he said to wait an hour then reboot, I rebooted, several times now all coax devices, after the maintenance.
Still receiving the same speeds and now I see errors on the modem event log on my MT8733, the log doesn't go very far back, but it appears these errors started today.
With 2.5gb ethernet I am getting:
1067mb down 23.5mb up - On google speed test
1181mb down 24.3mb up - On xfinity speed test
Broadband Facts state typical speeds for this plan average:
2008.2 mbps down
306.02 mbps up
The errors I am seeing on the MT8733 are the following:
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing
US_Diplexer_Mode_Change:MDD-TLV21,85
US_Diplexer_Mode_Change:TLV-84,42
US_Diplexer_Mode_Change_Ignored:MDD-TLV21,85
UCD invalid or channel unusable
Research shows TLV-84,42 is the faster diplexer mode, and it looks like its falling back to MDD-TLV21,85
Elsewhere on this forum I saw one solution and one followup where after posting an employee said he sent a private message for similar issue:
"Have a CSR check the modem's speed provisioning / bootfile, and the backend account data as well"
Anytime I try to reach technical support through xfinity assistant it never connects me to someone, posting this looking for technical support, I also had an additional home phone line added (re-added as it got removed in a different customer service interaction a year+ ago) which didn't get assigned to the telephone port, but thats trivial as I want to port that number to different service just did it to put it in my name, and during this upgrade my order summary is wrong, but I will take care of that in person at the store today. I figure they wouldn't be able to investigate this speed issue at the store.
Please reach out, thanks
EG
Expert
•
109.9K Messages
3 months ago
That device is not compatible with their new Next Gen speeds. Only these third-party / retail purchased devices are so far;
2
diozqwin
5 Messages
3 months ago
Okay, so what I've been able to figure out looking at the Arris G36 as an example is that like the MT8733 both are DOCSIS 3.1 and both support 2 OFDM channels each upstream and downstream on the coax cable. Both must be able to do TLV-84,42 obviously the MT8733 can because it wanted to switch, it gets pretty complicated beyond this. Even more tedious to research because OFDM(A) is a term used for both wireless and coax modems, but in general the DOCSIS 3.1 modems are rated to theoretically reach 10Gb speeds.
I don't see any reason an Arris G36 would be better than the MT8733, in fact its much worse. The G36 uses Intel Puma 6 chipset which has known issues so far as websites making guides to not buy any modem/router made with them as they have random lag and connectivity problems. While MT8733 uses the MediaTek MT8733AHA or some variation of it, with 4 core A53 Cortex 1.5 Ghz ARM processor. And Arris G36 has an AX3000 wireless system while Motorola put in a AX6000 which is essentially double the speed
I can't really find any recognizable compatibility issue that would point to why MT8733 can't do the higher speeds, I would have to study for quite a while and all the information is not really directly accessible on all the modems.
I didn't like the idea of paying for higher speed that I couldn't use so I went and got the official comcast xfinity modem from the store, currently a Technicolor CGM4981COM v2 which uses a BCM3390 SoC (system on chip) to do DOCSIS 3.1 tasks which does seem like a promising improvement. This is combined with the Qualcomm IPQ6018 which I found to say uses 4 core ARM Cortex 53A as well, just at 1.8Ghz
Anyway, if you as a user read this, the take away is to avoid Intel Puma 6 and 7 chips / devices, I am suspicious that comcast would support Arris G36 with this chip for any other reason other than to point to it and say it is bad and get you to have their modem with the creepy Wifi detection feature that can sense people moving around the house. All in all I wish my Motorola MT8733 was supported, I would've paid the extra $30 a month to use my own equipment with unlimited data. It would really help the resale value of it too. Please hire some more engineers to do this unless the problem is with Motorola.
Generally I guess it would be wise to wait for DOCSIS 4.0 to come out to purchase a modem new again, and if you are looking to own your own there are plenty of modems around to get used, people on Ebay are selling MT8733 as low as $50, great modem in my opinion never had an issue besides comcast struggling to assign RJ11 voice lines, which they still struggle on their own official modem, mine is still down after doing the swap. Make sure to look through the supported list and scratch off anything Intel Puma 6 and 7
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