Category Archives: Tech

Technology in general

Intel J1900 flaw causing early failure for embedded devices

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This morning I woke up, made some coffee and went to the computer room to work on some projects when I noticed that the shared folders from my NAS weren’t showing up on my desktop. That’s odd I thought. I went over to the NAS and my fears were confirmed, not only was it offline, but it had an error light. It would power on, but it wouldn’t start up.

Hoping that this was some simple fault like a bad stick of memory, I disconnected the unit, pulled out the drives and brought it over to my test bench. I confirmed the power supply was good and swapped the memory in/out, but with no effect. Ouch, this thing is really dead I thought. Before consigning it to the e-waste bin, I thought I’d search around just to make sure and stumbled on a thread from 2020 about the CPU on these devices having a flaw. Not only that, there was a possible fix! (if, perhaps only a temporary one)

At the time the flaw was discovered Intel posted an addendum to their CPU specification update for the J1900 and related CPUs. (Intel has since removed these docs from the public facing side of their website and requires a CNDA account to access them. Thankfully the wayback machine has an archive of them linked above) Unfortunately, the problem lies in the silicon of the CPU itself and is not repairable.

The fix documented in the forum link above and in a similar Reddit thread a year later both outline connecting a 100-200ohm resistor to pull the LPC clock signal to ground. Thankfully this signal is exposed on a pin header that also supplies a ground pin on the NAS model I have. I first hooked up my oscilloscope to the clock pin and verified that it was operating out of spec. I rummaged through my component collection and found a 180ohm resistor that would work. I had some jumper wires with dupont connectors for another project and used that to make a dongle that would jump these 2 pins. I put power into the unit and it started right up. Amazing!

Sadly the problem with the J1900 CPUs is only going to get worse over time. It’s possible that I could be able to keep the unit running for some time, possibly by changing out for different resistors in the future as the circuit continues to degrade. However the real solution is to start planning a migration from this device to something new.

If you have an embedded device powered by a J-series, N-series or similar and it’s been operating 24×7 for several years, you’re likely on borrowed time. Get a good backup of your data and start planning your migration now.

VMWare aquisition chaos continues

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Broadcom has terminated all VMWare partners and won’t say if they’re going to be let back in. This move has angered customers and partners alike.

It’s sad to to see this company being so horribly mismanaged. Broadcom should slow down and carefully consider their next actions before they alienate their customers and risk losing much of the value they hoped to extract from the company.

Yellow glue, a problem waiting to strike your vintage electronics

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Many in the retro-computer community are aware of the dangers of Varta rechargeable batteries found on many older computer mainboards. These permanently soldered-on components have a tendency to leak as they age and wreak havoc as the acidic fluid corrodes and dissolves the copper traces on the board. As I learned today, there’s another hidden foe that may be lurking in some of your devices, particularly power supplies. This evil substance is a type of yellowish glue.

Yellow glue isn’t silastic, the typically white non-conductive silicone-based adhesive found in some higher quality applications. It seems to be possibly some type of neoprene rubber adhesive that is cheap and sets quickly making it a popular choice for low cost manufacturing of electronics. It’s typically applied to glue components in place for assembly, insulation and protection from vibration. The down side is that this material ages poorly, especially in hot environments and becomes hygroscopic. Once this happens, the material becomes partially conductive as it absorbs water which can lead to some pretty dramatic failures, especially if the material is on a mains or high voltage part of a circuit board.

I discovered this issue on some power supply boards I was troubleshooting. I had been going through the process of reworking them and was checking all of the components prior to powering up. One of the probes to my multimeter slipped off the diode I was measuring, but to my surprise I was still getting a reading. I jammed both probes into the browning mess of old glue and what do you know, it was conductive! It measured over a mega-ohm, but it was consistent. I started checking the other spots of glue and any that looked darker and crusty were conductive.

The other downside of this material is that it’s very difficult to remove without damaging components. In my application, I was able to use some stiff plastic spudger tools to scrape it away. It was very labor intensive and didn’t entirely remove it. I may try something like acetone on individual components like inductive coils, (to attempt to dissolve and remove it) but unsure if this would be safe to just douse the board with.