Cable ISP backend equipment

[marshallh]

A while ago I obtained several Motorola RX-48 CMTS boards.
They're from 2010-2011, and convert DOCSIS 3.0 to local ethernet, with focus on upstream bandwidth.





8 analog frontends. They run the back ganged coax connector, with test points connectable via jumper.
Netlogic chips are dedicated set-associative RAM, for routing tables.
POL modules favored for high current capacity. The Ericsson SMPS module that looks like a battery backed EEPROM is a ~150 watt converter.

Each QAM baseband processor has 2 GigE interfaces and 1gb DDR3.
Vectron timebase is vendor-customized for DOCSIS interfaces supplying 10MHz, 123.5MHz, 250MHz.



Motorola MPC PowerPC processor with external PCI to PCIe bridge. They use custom ram modules which were removed before decommission.



There is a lot of bypassing on the back. No fewer than 17 debug headers.

Lots of bypassing.

The reason I bought them:



BTW, if you want to have some fun, try counting the number of fuses. I count 25 but could be wrong.

[poorchava]

How many layers (approximately) does that PCB have?

[dr.diesel]

When cost is irrelevant, nice!

[jeremy]

for the record: http://www.digikey.com/product-search/en?vendor=0&keywords=EP4SGX230KF40C4N

[marshallh]

I couldn't find a layer guide on the PCB but I'd guess around 16-24 layers.
What's interesting is that while they got filled vias, they didn't use them really, for the BGA bypassing they could've made their job much easier.

[PA0PBZ]

BTW, if you want to have some fun, try counting the number of fuses. I count 25 but could be wrong.

In the picture right above that statement there is F32, so it could be that there are a few more...

[coppice]

When cost is irrelevant, nice!

In telecoms hardware cost is extremely relevant, because it represents up front investment with a fairly long payback. This unit is no more complex or expensive than it needs to be.

[amyk]

for the record: http://www.digikey.com/product-search/en?vendor=0&keywords=EP4SGX230KF40C4N

I wonder why they sell the NES version which is apparently an "engineering sample"... for $120 more.

In telecoms hardware cost is extremely relevant, because it represents up front investment with a fairly long payback. This unit is no more complex or expensive than it needs to be.

I suppose that's why they use the slowest version of the FPGA.

[SeanB]

Probably the slowest because it is likely the lowest power version and does the job. Power use is very important, more so than price. If you save 2% in power over the life of the equipment that more than covers the whole cost of the unit in many cases. I see much of this infrastructure is aiming to be fanless, just to get the ability to be fitted into a sealed enclosure to keep the inside clean and dry. Otherwise you will need to have an enclosure with a heat exchanger integrated into it to transfer heat without the electronics being exposed.

[deian]

Great photos! Especially the one with "Lots of bypassing".
What are you planning to do with the FPGA?
 

[KJDS]

Probably the slowest because it is likely the lowest power version and does the job. Power use is very important, more so than price. If you save 2% in power over the life of the equipment that more than covers the whole cost of the unit in many cases. I see much of this infrastructure is aiming to be fanless, just to get the ability to be fitted into a sealed enclosure to keep the inside clean and dry. Otherwise you will need to have an enclosure with a heat exchanger integrated into it to transfer heat without the electronics being exposed.

It's been a key issue in cellular basestations for a long time.

A big cell tower cabinet used to run 14kW. There's roughly 5,000 of them in the UK. That's 70MW of electricity for 10k hours a year, at 15p a unit.

I don't fancy paying that electricity bill, but I have certainly contributed to it.

[SeanB]

The little cellular site by me has 48000BTU of air conditioning, using 2 24000 BTU units. It generally runs only one at around a 5% duty cycle, though we did have them turn the AC up to 24C instead of the 16C they left it on, as it was causing the walls and flooring above it to sweat in our humid summer. Never been around for service calls though, wonder how much they have crammed into that 3m by 4m room it is in. Has cellular as well as wifi inside, with it's own fibre cabling. Even has provision for an external generator, though it is not present, but has to be brought on site if needed.

[Stonent]

for the record: http://www.digikey.com/product-search/en?vendor=0&keywords=EP4SGX230KF40C4N

Holy Quadrature Amplitude Modulation, Batman!

[krivx]

Will those fpgas be re-worked onto new PCBs?