VM – Experimental Engineering

I posted a while back a teardown of the VM Superhub 2 router, as VM has “upgraded” to a rebranded Arris TG2492S/CE CM. Alas Virgin Media in their wisdom have decided that simple router features like being able to change the LAN subnet & DHCP server range are far too complex to trust to the Great Unwashed, so they’ve removed them entirely from the firmware, and locked the local LAN onto the 192.168.0.0/24 range.
As my network is already numbered in the 10.0.0.0/16 range, with several statically addressed devices present and other systems relying on these static assignments, using this router would have meant renumbering everything.

Luckily Virgin had the decency to leave the “modem mode” option in the firmware, effectively disabling the WiFi & routing functions & allowing the connection of a third-party router. Some searching for a suitable replacement for the core of my network turned up the Linksys WRT1900ACS. While I waited for this to arrive, some temporary workarounds were needed to make everything function well enough with VM’s crap router.

These routers have been designed as a modern replacement for the venerable WRT54G series of routers from some time ago, with full support for OpenWRT/DD-WRT firmware, and with a beefy 1.6GHz dual core CPU & 512MB of RAM I doubt I’ll be able to knock this one over with too much network traffic! This was pretty much the most powerful router I could afford, and should mean I don’t need to upgrade for a long time. (No teardown of this yet, as it’s taking care of the network at present. Maybe some point in the future I’ll take the plunge).

The stock firmware isn’t totally awful, and has some nice features, but I decided it needed to be replaced with DD-WRT for more security & future flexibility. I’ll leave the firmware flashing stuff for another post 😉

I recently got the latest upgrade from Virgin Media, 200Mbit DL / 20Mbit UL, and to get this I was informed I’d have to buy their latest hardware, since my existing CPE wouldn’t be able to handle the extra 5Mbit/s upload speed. (My bullshit detector went off pretty hard at that point, as the SuperHub 2 hardware is definitely capable of working fine with 20Mbit/s upload rates). Instead of having to return the old router, I was asked to simply recycle it, so of course the recycling gets done in my pretty unique way!

The casing of these units is held together by a single screw & a metric fuckton of plastic clips, disassembly is somewhat hindered by the radio antennas being positioned all over both sides of the casing. Once the side is off, the mainboard is visible. The DOCSIS frontend is lower left, centre is the Intel PUMA 5 Cable Modem SoC with it’s RAM just to the lower right. The right side of the board is taken up by both of the WiFi radio frontends, the 5GHz band being covered by a Mini PCIe card.

The 4 gigabit Ethernet ports on the back are serviced by an Atheros AR8327 Managed Layer 3 switch IC, which seems to be a pretty powerful device:

The AR8327 is the latest in high performance small network switching. It is ultra low power, has extensive routing and data management functions and includes hardware NAT functionality (AR8327N). The AR8327/AR8327N is a highly integrated seven-port Gigabit Ethernet switch with a fully non-blocking switch fabric, a high-performance lookup unit supporting 2048 MAC addresses, and a four-traffic class Quality of Service (QoS) engine. The AR8327 has the flexibility to support various networking applications. The AR8327/AR8327N is designed for cost-sensitive switch applications in wireless AP routers, home gateways, and xDSL/cable modem platforms.

Unfortunately most of the features of this router are locked out by VM’s extremely restrictive firmware. With any of their devices, sticking the VM supplied unit into modem mode & using a proper router after is definitely advised!

The cable modem side of things is taken care of by the Intel PUMA 5 DNCE2530GU SoC. This appears to communicate with the rest of the system via the Ethernet switch & PCI Express for the 5GHz radio.

The 2.4GHz radio functionality is supplied by an Atheros AR9344 SoC, it’s RAM is to the left. This is probably handling all the router functions of this unit, but I can’t be certain.

A separate Ethernet PHY is located between the SoC & the switch IC.

The 5GHz band is served by a totally separate radio module, in Mini PCIe format, although it’s a bit wider than standard. This module will probably be kept for reuse in another application.

All down the edge of the board are the multiple DC-DC converters to generate the required voltage rails.

The DOCSIS frontend is handled by a MaxLinar MXL261 Tuner/Demodulator. More on this IC in my decapping post 🙂

I’ve honestly no idea what on earth this Maxim component is doing. It’s clearly connected via an impedance matched pair, and that track above the IC looks like an antenna, but nothing I search for brings up a workable part number.

The RF switching & TX amplifiers are under a shield, these PA chips are SiGe parts.

Pretty much the same for the 5GHz radio, but with 3 radio channels.

Tag: VM

Virgin Media Hub 3 Crap & Router Upgrades

Virgin Media Superhub 2 Teardown