Just some JTAG related randomness, considering that I’ve touched on it in previous post.

Linksys WRT54Gx

Linksys WRT54G and WRT54GS have JTAG headers on motherboard. It is possible to solder on the pins into the header on the motherboard, and build a Wiggler style cable to re-flash the bootloader, if you ended up hoseing it.

Personally I’ve done it on two WRT54GSes, and one of the main changes I’ve done was to set the boot_wait variable to on by default in the boot loader.

As Wiggler hooks up over parallel port, and thus is slow as sin, reflashing anything but the bootloader (ie flashing in actual firmware over JTAG) would take days.


CS6400 had an Sbus based JTAG interface for hardware tests. CS6400 was a Cray Research Superservers Inc.’s Cray Superserver 6400. If I remember correctly, it had up to 8 XDBuses, and up to 64 either 75 or 85Mhz SuperSPARC II mBus based CPUs (same ones that could be used in Sun SPARCstations 10s and SparcStation 20s).
These were rather elusive beasts, and while I used to own a SPARCserver 1000 (12.5 amp/hr space heater, that sounded like a jet taking off), and there was SPARCserver 2000 (rackfull of 3-phase joy) that I played with, I’ve never touched a CS6400.

In fact, I suspect that few people at Sun even knew what one was – there were some parts schematics and option lists printed in the paper versions of Sun Field Engineer Handbooks, but as CS6400 was a product that Sun inherited when Sun bought Cray Research Superservers/Floating Point Systems from SGI. Sun used the Cray technology to build shiny things like Enterprise xx00 (Campfire) and Enterprise 10000 (Starfire) product lines.

JTAG was the primary way of hardware diagnostics on E10K, and was connected to System Service Processor (SSP, commonly an Ultra 5)

P.S. Sun, why did you block off wast majority of useful FEH content to subscribers only? On, and Sun, will you sue me if I dig out an older version of FEH that you guys used to ship on a CD, and make it available on the interweb?

I distinctly remember using JTAG to recover something else in the past, however my memory fails me. Might have been Nokia cell phone, might have been some sort of uPCI x86 system.