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xymox1
Premium Member
join:2008-05-20
Phoenix, AZ
ARRIS SB8200
MikroTik CCR1036-8G-2S+

xymox1

Premium Member

Re: Upgrade from dpc3000 to dpc3010 and slower upstream speeds

Well the "new" dpc3010 i got was actually a older manufacturing date then the one I had already But thats just fine as I had already gotten the new firmware on the orginal one.

I went ahead and did some mods. Changed out the heat sink on the broadcom QAMLink BCM3380DKFSBG TN1136. It was a crummy heat sink. I used a real one with more surface area. I also mounted a small fan directly above the heat sink in the case. This dramatically lowered the chip temp.

I also did a number of mods to the power supply rails that feed the various sections. I added 6X the uF of the power supply caps and used tantalum caps. This had the effect of dramatically lowering the noise on the power rails to the various sections. The caps I put in cost more then the modem ! and of course thats why they could not use this quality of part. The power supply rails are now very clean and have very little noise.

The S/N on the status page gained 1db, which was suprizing as I would not have expected to see much performance increase but there was

The mods were meant to make the modem far more stable and happy, not so much increase performance.

I like that the DPC3010 has a shielded ethernet connector for use with shielded interconnects. I use cat 7a and these cables are always shielded.

Off to do more testing. First tests show rock solid 65/5.8. The 5.8 is surprizing and its consistent. It was only showing 5.5 before the mods so the mods might have made the modem a tiny bit better performance.

I will have pics later tonight.

Very consistent.
xymox1

1 edit

xymox1

Premium Member

Some pics...

The DPC3010.




RF section...




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.

xymox1

3 edits

xymox1

Premium Member

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.
xymox1

xymox1

Premium Member

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..
xymox1

xymox1

Premium Member

HMMMmMmmmmmmmmm.....

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.
lilstone87
join:2009-04-09
Chesapeake, VA

lilstone87

Member

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.

xymox1
Premium Member
join:2008-05-20
Phoenix, AZ
ARRIS SB8200
MikroTik CCR1036-8G-2S+

xymox1

Premium Member

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.