Under The Covers

Figure 3 shows the main board of the unit. Processing is provided by a pair of PMC-Sierra chips, the PM8172 System Controller and RM7035c MIPS processor.

Figure 3: NSS4000 Main Board

The SATA controller on the unit is a PDC40518 from Promise Technology. I couldn't make out the chips providing the gigabit Ethernet support as they were covered by heat sinks.

As for software, Linksys advertises that the unit runs Linux internally so that is no secret. Linksys also has a GPL download web site so you can explore the components included on the box. The Linksys NSLU2s I use have had their firmware heavily modified, so I wondered if the NSS400 could be similarly customized. To check it out, I downloaded a firmware image from Linksys and noticed it was a simple compressed tar file. Expanding the tar file revealed a couple of familiar files: a Linux kernel and a Linux root filesystem image.

There was also another tar file that when uncompressed revealed some standard Linux startup scripts and a script that appeared to be run at firmware installation time. Digging into this script revealed that there was an embedded-ssh server, dropbear, on the box.

A network probe of the box showed that it wasn't running, but a "gpio.conf" file included in the firmware seemed to indicate that the server would be started if a jumper was placed on a particular GPIO pin. I didn't have time to investigate this further. But Terry Kennedy's blog page identifies the enabling jumper as J34 and has other details on the NS4000's innards.

Tags: Linksys, NAS, RAID,

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