|reply to xymox1 |
Re: Upgrade from dpc3000 to dpc3010 and slower upstream speeds
I changed the heat sink to a better one, used silver based heat sink compound. You can see the 3 2200uF caps and the silver wet tantalum 560uF cap..
A bunch of big 100uF solid tant added here.
There was obvious cost savings on the board. There were places for caps but these were not populated as im sure cost was a factor.
The fan is fugly, but very functional. I used Silenx. Its powered from inside the modem.
While the DPC3000 is now not a consideration I figured I would put up test results just in case anyone ever cares..
The speeds at 65Mb/s / 5.5Mb/s were identical. The 3010 might have edged out the 3000 every so slightly un upload speeds. I think this is because the Broadcom CPU is faster then the TI in the 3000 and therefore can do the cap rate limiting in a more nimble fashion. Simply the CPU can respond faster doing things like ACK.
The differences however are clear in latency and jitter. Mostly jitter.. I took 2 samples from Multiping and put them together for easy comparison. The 3010 clearly has less jitter which results in a lowered averaged latency. This shows 2 15 min long samples.
So the 3010 is better at a smoother connection with less jitter. This is important for gamers and maybe VoiP.
Ive now confirmed the above mods did make a difference, somehow I can get slightly higher upload speeds. Lower noise floor ? Who knows exactly. But before the mods I 100% of the time got 5.5Mb/s up and now I 100% of the time get 5.8 and sometimes as high as 6. Not that big a deal but surprizing considering the mods...
Now I await the SB6180. It will be fun to test that and see how that performs...
The test setup is:
PC connected directly to modem. No router. No other software execpt Multiping. Multiping set to 0.1 ping interval.
PC Intel i7 X990 @ 4.5Ghz 6 cores, ASUS Rampage Extreme IV motherboard, triple channel high performance ram, Adaptec SATA raid controller doing RAID 0 with 2 SSD drives. Intel MB based Ethernet - gigabit. Capable of wireline speed.
For large transfer tests I use a PC based router running Vyatta. The router is capable of 1 million packets per second and does wireline speeds with any packet larger then 128 Bytes.
OK I got my SB6180 online. Im starting tests. I have requested that my firmware be updated.
Right outta the box its as fast as the DPC3010. While I need to do more tests I cant find any differences in performance..
After looking at the board I know why.. They are IDENTICAL... Yea thats right, IDENTICAL.. While the layout of the boards is a little different, EVERY RESISTOR, CAP AND SEMI is -EXACTLY THE SAME -. In fact THE PC BOARD LAYOUT PART NUMBERS ARE EXACTLY THE SAME. R203, C305, this are EXACTLY the SAME on both for every part and the vaules are the same. There are some minor differences. The DPC3010 has a USB port while the SB6180 has a PROM for storing its far more extensive GUI menu structure.
The layout is different with the SB6180 looking like it might have a better layout and topology for its RF section.
The internal power supply is different between the two in one respect. The SB6180 lacks any caps for filtering on the rails. While this will clearly be way more noisy in the long term with as much heat as comes from the BCM3380 it will slowly over years dry out electrolytic caps so not using them and making it work without them is a good idea long term IF you have a lot of heat. In my case with my fan this is not a consideration and if I decide to keep the SB6180 then I will be adding lots of caps and making the power rails MUCH quieter.
The DPC3010 was made in China and the SB6180 made in Korea.
So how in the world did both these modems end up with exactly the same schematic, parts, part designations on the PC board ? THEY HAD TO HAVE COPIED.. I feel they simply copied the Broadcom suggested EVERYTHING. Copy pasted the whole schematic right from a Broadcom datasheet.
So I dont expect to find any differences in performance between the 2 as they are exactly the same in every visible way. Its possible tho that the firmware is different and thats important, so I will do all my same tests...
There are a few differences worth note. The RF section in the SB6180 *might* be better. But its close. The SB6180 has a better heatsink and this will help long term lifetime. The DPC3010 has a better power supply internally but after 5 years of use might not be as good.
I am awaiting my firmware grade, once its upgraded i will start longer term and more extensive tests.. I may not report the results until next week..
I was just noticing that the DPC3010 reports a S/N of 39-40 but the motorola is reporting a S/N 29-31... 10db is a LOT of difference in S/N
As its coming from the same bcm3380 I would think its calculating the S/N the same way.
10db is alot. Maybe its the SB6180. Its a used one. I suppose I will have to order up a new one. I like the 6180 simply because of the GUI as no other performance measurements seem to be any different. However 10db of S/N is a whole lot.
The 3010 and 3000 have the same levels, the 6180 has 1db higher for downstream level and shows a lower upstream power. As the RF sections are quite different in layout and shielding it makes sense they have different numbers. 10 db of S/N however is a huge difference.
Maybe its just a bad used modem.
Have you got the firmware updated yet? Either there is some kind of bug, or the modem has issue's. I would think more of a bug, reason I ask if the firmware has been updated yet. If it hasn't leave it online overnight for the firmware to be updated. Also have you reset the modem to defaults threw the modem page, and reset the modem? To see if the snr will correct itself? I seen my D3 eMTA do this recently, showing downstream snr's at around 30-31db, and a simple modem reboot fixed this error.
I got the ever competant CoxVegas rep to update it for me. Yes the firmware is updated.
I think its the modem. It was used and it looked pretty used looking at the inside. Degraded S/N woulld be a normal sign of some stress on the electrical input from the RF, say a surge or lightning. Funny they replaced the case but the modem itself was in very marginal shape. Thats what I get for buying a used modem off ebay. Well it was $40 and I can play with it to learn things and see how it performed.
It performed great even with the degraded S/N. Maybe a tiny bit faster then a DPC3010. Maybe. I will get a brand new one as I like the detailed stats in the GUI. I also like the ethernet jack, its Amphenol. I like the board layout better. There is more room in the case. I like the way they layed out and isolated the RF sections. I can add some great stability mods and have nice amounts of room.
I have to go outta town for work until next week so i will not be able to get a new SB6180 until after that. I will do a complete set of tests and if its the equal of the DPC3010 will mod the 6180, add a fan and make it my modem.
Overall tho its safe to say these 2 modem are almost identical. I doubt anyone would see any difference in real use at all. The only suggestion I have is to make sure they get lots of ventilation. Heat can kill these boxes quite easily.
|reply to xymox1 |
Wow! I will have to say this is the most anal retentive thread about a modem I have seen. I am picturing all any every electronic on your home having mods done to them. Nice job!!
Well yes, I do mod a lot of stuff. Usually only analog based stuff as digital stuff does not really benefit from mods. A cable modem is a very analog device. Its receivers and transmitter are very advanced analog devices.
Also i figured google will find this thread and others may want to know the differences in the SB6180 and DPC3010.
Its really just a blog as I do what I was going to do anyway in getting the best network connection I can make.
The BCM3380 is capable of 500,000 packets per second so I want to be sure my whole network can do those speeds. My router can do 1 million pps and wireline speeds along with the computer, so my weak link is the cable modem and what speeds my ISP can provide.
Im so crazy i run a fast Debain based server just for running my recursive caching DNS server.
My network as a whole is lightning fast. I want my cable modem to be as fast as humanly possible. ALSO fast does not mean download and upload speed. There are all sorts of things that go on with communications, error correction, protocols and all sorts of stuff that effect how fast each TCP/UDP connection is setup and broken down and how all that is done over DOCSIS. All that effects perceived "speed" of the connection.
Very cool work. Would love to buy a modded out SB8160 from you, if you have time to make one. huddh (you know the rest since I'm a cox.net customer). Thanks.
|reply to xymox1 |
Im not sure the mods make any difference. If they do, its a very small difference. Also im not sure what long term effect the mods might have.
So... I cant find any difference at all between a SB6180 and a DPC3010 performance wise. Well,,, with my limited tests. You would need very sophisticated test gear to fully test these devices. Like what Cable Labs has. Some independent testing lab should test modems and publish specs so we can all see differences. NO ONE does this. The specs are all secret.
Ive decided on the DPC3010. The reason is that Cox seems to be supporting them more as its all they sell and install in my area. Also in real life im not going to be looking at any of the GUI's that the 6180 has. If I do ever want to look I have a 6180 I could hook up. I also like the DPC3010 power supply and board layout better. The 6180 *might* have a better RF section tho. I have no way to test or measure this.
Ive done further mods to mine and I think I have improved performance when signals are really bad. I would get weird results below -12db before mods and now I can get down to -18 down and 57 up and still get what seems pretty normal performance. Sometimes at those levels tho I only get 2 upstream channels rather then 3.
Ive got some attenuators coming and im going to more accurately test my performance at various levels. I also have a unmodded dpc3010 to use for comparisons.
There is no doubt the modded modem works much better on bad connections. But levels of -15 and 56 db should be corrected in the wiring or with the cable co.
It does show however that far less noise on the supply rails to the BCM3380 does improve performance. However mods make no difference whatsoever with normal signal levels. Someone back there knew more filtering of the supplies did matter as there are places for much better filtering on the PCB but these are not populated. No doubt a cost saving step.
The one mod i would recommend to EVERYONE using one of these modems is a small fan. These things run way too hot and a small fan makes a huge difference. Also a better 12V power supply is a good idea. I use a 12V 3A with good regulation.
I will update this more once I get my attenuators and do some more testing.
Las Vegas, NV
Starting to sound like some of the frankenmodems we have sitting in our modem lab here. (We take some apart, have cables hanging out of some for measurements, etc. etc.)
|reply to xymox1 |
Well you have a HUGE advantage. The right test gear AND you can get the datasheets for a BCM3380. Its kinda crazy there is so much secrecy around those chips.
Because the chip is a all-in-one affair there is not much to do. Clean up power supplies is about it. Cant touch RF as thats way too complex and I am sure no QAM expert and dont have the gear to test it.
So all I can do is make the power supplies happier.
Of course you could tweak internal settings, adjust all sorts of stuff internally, do custom firmware... However I dont think there is anything that would really improve performance. The modem is capable of 300Mb/s and at most we will be getting 100Mb/s thru it.
I suppose, if a modem were made from scratch with a far more powerful CPU it might be possible to lower latency a bit because the modem could process packets faster. I wonder how fast it is currently doing small packets ? Say a 64 Byte Frame ? Doing 1518 Byte frames is one thing, 64 Byte Frames is another. Its now possible to buy a $99 router that can do 1 million packets per second at 64 byte frames. The BCM3380 sheet says it can do 500,000 pps but does not specify what size frames and more then likely its much larger frames. The router has dual cores and uses a MIPS64. »www.ubnt.com/edgemax#EdgeMAXhardware
It important to remember that pps and frame size are the right way to evaluate a router and im sure that must extend to a cable modem. Just because it can do 300Mb/s at 1518 Byte frames does not mean it can do it at 64 byte frames.. Small frames are actually used quite a bit too, like DNS lookups.
Of course if the modem is being used as a gateway with NAT and a firewall all from the BCM3380, like a SB6580, then there is a bigger problem as the chip now has to also do all the networking as well. I believe in a separate modem and router.
On a whole different note.. I like using those little filters that the Cable Co has that filter out cable TV channels. I have 1 filtering out all that TV junk right before the modem. I feel its best to not feed the modem any more RF then it needs. Those little filters do a great job of removing all the stuff except the cable modem signals If you ask nicely the cable guy might give you one or 2. They are only a 1db insertion loss in the modem signal band but suck out like 50db of the entire specrum of TV channels and digital cable tv. Less stuff into the cable modem RF front end is always good.
Well after lots of playing around I am pretty solid with a DPC3010. I had some talks with some Cox people and they told me they see firmware updates from Cisco much faster and more often then from Motorola. Also the CMTS gear in my area is Cisco and I would think it might be better to use a cisco modem with a cisco CMTS.
So for those reasons I am going to stick with a DPC3010.
I have now played with 4 DPC3010's and 3 SB6180's. I was interested in what variations occurred between units. This actually did vary. I saw 3 db differences in levels in up and down stream.
In the mod department I decided to replace the 48Mhz crystal with a far better and tighter tollerance Xtal. The crystal in there now is a 100ppm drift part and I decided on using a 10ppm part. 10 times lower drift.
HOWEVER I was shocked when I measured the frequency of the current xtal. It measured 48.000000062 mhz and drifted around a center point that was almost the equal of my rubidium based freq counter ! I tried another dpc3010 and another. They were all very close to this ! This is a startling absolute precision for such a device. The only way this could really be is if there was some way to trim the freq in software in the bcm3380.. A software based calibration. That MUST be what occurs.
So that means during production a calibration must occur with some pretty serious test gear. That brings to mind what else gets calibrated ? Output levels, input levels, QAM settings.. Each modem must have its own unique calibration.
I should would like to be able to send off my modem for a careful calibration somewhere.
So the crystal upgrade is not possible as I cant software calibrate the BCM3380 to the new crystal
I think I have reached the end of my mods and my selection journey.
Now if only Cox would turn on 100Mb/s service and 8x4...
said by xymox1:I couldn't agree anymore but don't see it happening anytime soon with the only competition in the valley being century link!
Now if only Cox would turn on 100Mb/s service and 8x4...
quote: Its at most a month or 2 away. Its supposed to be first part of January.
but don't see it happening anytime soon
I didn't know but this would be sweet. Do you know what the upload is going to be bumped up to as well?
*Rumor* has it that it will be 100Mb/s down and 10Mb/s up. With speedboost and if you have the ultimate tier of service.
Also I would assume on a good day.
My 65Mb/s down and 5.5 up is rock solid now so I hope that 100/10 will be rock solid as well.
I test using speedtest.net and I use the San Jose server Smug Mug as its the fastest for some reason on the cox network from phoenix.
I get similar results from San Jose or Scottsdale which is funny.
Lets hope the rumors are true but I would like a slightly higher up load
The San Jose Smug Mug is more consistent if you do it a lot. Which i sure have..
The 10Mb/s is *supposedly* a cap and the only way to get more is to get a business acct where you will *supposedly* be able to get 20Mb/s..
Thats rumor and Cox will not confirm or deny. However that seems to be what other people are reporting in other Cox cites when they switch on 100Mb/s..
I do have a business account as well so we shall see what Cox plans to do.
|reply to xymox1 |
This was a very interesting post, thanks for sharingso much details!
well im not actually done yet. I got a very recent production SB6180 last week. It had some production changes and had some caps right where i decided to put them ! Only 2 tho where I have now put 17 all over in key spots.
But this caused me to look over and test the sb6180 all over again.
In fact I dont think its a equal to the dpc3010. While the RF section *might* be better the poor design of the power supplies to the BCM3380 is a big oversight. The fact they had to add caps later in production - tacked down with silicone - is clearly a rather emergency measure to fix a known issue hurridly rather then do a board redesign.
The complete lack of electrolytic caps on the power supply rails to the chips is almost bizarre. Measuring the noise on these rails reveals what seems clearly like too much noise for proper operation.
I would think this would result in strange behavior, more then normal reboots and hangs.
I also now see another big difference bewteen the dpc3010 and sb6180. Under the bcm3380 chip are small caps on the power leading into the chip. These are standard stuff on any CPU. They keep noise out of the power going to the CPU. On the SB6180 the values of these caps is 10 times smaller then on the dpc3010. In fact they are so small it seems really weird. When you add on to that the lack of electrolytic caps after the regulators then this design seems dangerously noisy.
So my opnion now is that the DPC3010 out of the box is a superior device from a engineering stand point.
Also the DPC3010 is much easier to mod and add further tweaks to to make it even better.
Now BOTH the SB6180 ( and 6580 ) and the dpc3010 ( dpc3825 ) have SERIOUS thermal management issues and run WAY TOO HOT. Ive now clearly seen that older units rather quickly loose performance as the heat bakes the bcm3380 and degrades its RF performance. All the used older modems I have seen all have degraded RF performance and this must be related to the bcm3380 and I feel heat. So the addition of a fan to blow the heat outta these boxes will keep performance up over the life of the unit. Not to mention the huge increase in lifetime cooling the BCM3380 down will provide. The complete stupidity in allowing these super high temps on this chip are just stunning. These are all going to fail.
Overall I dont like the design and layout.
HOWEVER there is one very important thing that might make the SB6180 a better choice, a better heat sink. The sb6180 is far more likely to survive longer from the excessive heat then the 3010. The thermal management on the 6180/6580 is better and this alone might be a reason to buy it over the 3010...
Adding a small fan to these tho then makes the 3010 the better choice as it has better electrical design and better firmware support.
The above is my final conclusion.
dvd536as Mr. Pink as they comePremium
|reply to xymox1 |
current firmware is may 16 2011. your firmware is old.
Despises any post with strings.
Yes, as is covered in the thread many posts ago my firmware was old. Important to read the whole thread before posting. In fact there is a *** UPDARE *** i put on the very first post that says that.
|reply to xymox1 |
I acquired a DPC3010 when Cox first started offering them for free and my experience was poor.
First, I discovered that the Cox caps were much stricter on the DPC3010 than on the SB6120. In fact, for about a year, I experienced a 20-35Mbit powerboost advantage over the 55mbit limit on the DPC3010. However, that advantage was eventually and rightfully taken away by an update.
Secondly, and most importantly, my DPC3010 was always flakey. Which I found very odd, especially b/c the DPC3010 always had 3-4db advantages (higher SNR 4+db) (lower upstream -4db) compared to my SB6120. I think you hit the nail on the head with your analysis of the the deficient heatsink in the DPC3010. At the time, it was not unheard of to be 1-2+Tbytes/month, and my guess is it overworked the broadcom chip and things got too hot in the DPC3010, which caused it to flake out.
Switching back to the SB6120 always resulted in a rock solid and stable connection in comparison.
|reply to xymox1 |
At first, I was like this guys a little crazy. But, then I realized he's just my kind of crazy. Awesome thread. Xymox1, if you ever get into router modding, would be an insanely interesting thread. Only thing I wish you would have done differently was figure out a more aesthetically pleasing design scheme for your frankenmodem fan mod.
Btw, xymox1, how often are you calling in to get your account's MAC switched?