etbe - Russell Coker

USB-PD and GaN

A recent development is cheap Gallium Nitride based power supplies that provide better efficiency in a smaller space than other technologies. Kogan recently had a special on such devices so I decided to try them out with my new Thinkpad X1 Carbon Gen 5 [1]. Google searches for power supplies for that Thinkpad included results for 30W PSUs which implies that any 30W USB-C PSU should work.

I bought a 30W charger for $10 that can supply 15V/2A or 20V/1.5A on a single USB-C port or 15W on the USB-C port and 15W on the USB-2 port at the same time and expected it to work as a laptop charger. Unfortunately it didn’t, I don’t know whether the adverts for 30W Thinkpad PSUs were false or whether the claim of the GaN charger I bought being 30W was false, all I know is that the KDE power applet said that the PSU couldn’t supply enough power.

I then bought a 68W charger for $28 that can supply 20.0V/3.0A on a single USB-C port if the USB-2 port isn’t used and 50W on the USB-C port if the USB-2 port is also being used. This worked well which wasn’t a great surprise as I had previously run the laptop on 45W PSUs. If I connect a phone to the USB-2 port while the laptop is being charged then the laptop will be briefly cut off, presumably the voltage and current are being renegotiated when that happens.

As you can see the 68W charger is significantly larger than the 30W charger, but still small enough to easily fit in a jacket pocket and smaller than a regular laptop charger. One of my uses for this will be to put it in a jacket pocket when I have my laptop in another pocket. Another use will be for charging in my car as the cables from the inverter to convert 12VDC to 240VAC takes enough space. I will probably get a ~50W USB-PD charger that connects to a car cigarette lighter socket when a GaN version of such a charger becomes available.

[1] https://etbe.coker.com.au/2022/12/08/thinkpad-x1-carbon-gen5/

Thinkpad X1 Carbon Gen5

Gen1

Since February 2018 I have been using a Thinkpad X1 Carbon Gen1 [1] as my main laptop. Generally I’ve been very happy with it, it’s small and light, has good performance for web browsing etc, and with my transition to doing all compiles etc on servers it works well. When I wrote my original review I was unhappy with the keyboard, but I got used to that and found it to be reasonably good.

The things that I have found as limits on it are the display resolution as 1600*900 isn’t that great by modern standards (most phones are a lot higher resolution), the size (slightly too large for the pocket of my Scott e Vest [2] jacket), and the lack of USB-C. Modern laptops can charge via USB-C/Thunderbolt while also doing USB and DisplayPort video over the same cable. USB-C monitors which support charging a laptop over the same cable as used for video input are becoming common (last time I checked the Dell web site for many models of monitor there was a USB-C one that cost about $100 more). I work at a company with lots of USB-C monitors and docks so being able to use my personal laptop with the same displays when on breaks is really handy.

A final problem with the Gen1 is that it has a proprietary and unusual connector for the SSD which means that a replacement SSD costs about what I paid for the entire laptop. Ever since the SSD gave a BTRFS checksum error I’ve been thinking of replacing it.

Choosing a Replacement

The Gen5 is the first Thinkpad X1 Carbon to have USB-C. For work I had used a Gen6 which was quite nice [3]. But it didn’t seem to offer much over the Gen5.

So I started looking for cheap Thinkpad X1 Carbons of Gen5+.

A Cheap? Gen5

In July I saw an ebay advert for a Gen5 with FullHD display for $370 or nearest offer, with the downside being that the BIOS password had been lost. I offered $330 and the seller accepted, in retrospect that was unusually cheap and should have been a clue that I needed to do further investigation. It turned out that resetting the BIOS password is unusually difficult as it’s in the TPM so the system would only boot Windows. When I learned that I should have sold the laptop to someone who wanted to run Windows and bought another. Instead I followed some instructions on the Internet about entering a wrong password multiple times to get to a password recovery screen, instead the machine locked up entirely and became unusable for windows (so don’t do that).

Then I looked for ways of fixing the motherboard. The cheapest was $75.25 for a replacement BIOS flash chip that had a BIOS that didn’t check the validity of passwords. The aim was to solder that on, set a new password (with any random text being accepted as the old password), then solder the old one back on for normal functionality. It turned out that I’m not good at fine soldering, after I had hacked at it a friend diagnosed the chip and motherboard to probably both be damaged (he couldn’t get it going).

The end solution was that my friend found a replacement motherboard for $170 from China. This gave a total cost of $575.25 for the laptop which is more than the usual price of a Gen6 and more than I expected to pay. In the past when advocating buying second hand or refurbished laptops people would say “what happens if you get one that doesn’t work properly”, the answer to that question is that I paid a lot less than the new cost of $2700+ for a Thinkpad X1 Carbon and got a computer that does everything I need. One of the advantages of getting a cheap laptop is that I won’t be so unhappy if I happen to drop it.

A Cheap Gen6

After the failed experiment with a replacement BIOS on the Gen5 I was considering selling it for scrap. So I bought a Gen6 from Australian Computer Traders via Amazon for $390 in August. The advert clearly stated that it was for a laptop with USB-C and Thunderbolt (Gen5+ features) but they shipped me a Gen4 that didn’t even have USB-C. They eventually refunded me but I will try to avoid buying from them again.

Finally Working

The laptop I now have has a i5-6300U CPU that rates 3242 on cpubenchmark.net. My Gen1 thinkpad has a i7-3667U CPU that rates 2378 on cpubenchmark.net, note that the cpubenchmark.net people have rescaled their benchmark since my review of the Gen1 in 2018. So according to the benchmarks my latest laptop is about 36% faster for CPU operations. Not much of a difference when comparing systems manufactured in 2012 and 2017! According to the benchmarks a medium to high end recent CPU will be more than 10* faster than the one in my Gen5 laptop, but such a CPU would cost more than my laptop cost.

The storage is a 256G NVMe device that can do sustained reads at 900MB/s, that’s not even twice as fast as the SSD in my Gen1 laptop although NVMe is designed to perform better for small IO.

It has 2*USB-C ports both of which can be used for charging, which is a significant benefit over the Gen6 I had for work in 2018 which only had one. I don’t know why Lenovo made Gen6 machines that were lesser than Gen5 in such an important way.

It can power my Desklab portable 4K monitor [4] but won’t send a DisplayPort signal over the same USB-C cable. I don’t know if this is a USB-C cable issue or some problem with the laptop recognising displays. It works nicely with Dell USB-C monitors and docks that power the laptop over the same cable as used for DisplayPort. Also the HDMI port works with 4K monitors, so at worst I could connect my Desklab monitor via a USB-C cable for power and HDMI for data.

The inability to change the battery without disassembly is still a problem, but hopefully USB-C connected batteries capable of charging such a laptop will become affordable in the near future and I have had some practice at disassembling this laptop.

It still has the Ethernet dongle annoyance, and of course the seller didn’t include that. But USB ethernet devices are quite good and I have a few of them.

In conclusion it’s worth the $575.25 I paid for it and would have been even better value for money if I had been a bit smarter when buying. It meets the initial criteria of USB-C power and display and of fitting in my jacket pocket as well as being slightly better than my old laptop in every other way.

Links November 2022

Here’s the US Senate Statement of Frances Haugen who used to work for Facebook countering misinformation and espionage [1]. She believes that Facebook is capable of dealing with the online radicalisation and promotion of bad things on it’s platform but is unwilling to do so for financial reasons. We need strong regulation of Facebook and it probably needs to be broken up.

Interesting article from The Atlantic about filtered cigarettes being more unhealthy than unfiltered [2]. Every time I think I know how evil tobacco companies are I get surprised by some new evidence.

Cory Doctorow wrote an insightful article about resistance to “rubber hose cryptanalysis” [3].

Cory Doctorow wrote an interesting article “When Automation Becomes Enforcement” with a new way of thinking about Snapchat etc [4].

Cory Doctorow wrote an insightful and informative article Big Tech Isn’t Stealing News Publishers’ Content, It’s Stealing Their Money [5] which should be read by politicians from all countries that are trying to restrict quoting news on the Internet.

Interesting articl;e on Santiago Genoves who could be considered as a pioneer of reality TV for deliberately creating disputes between a group of young men and women on a raft in the Atlantic for 3 months [6].

Matthew Garrett wrote an interesting review of the Freedom Phone, seems that it’s not good for privacy and linked to some companies doing weird stuff [7]. Definitely worth reading.

Cory Doctorow wrote an interesting and amusing article about backdoors for machine learning [8]

Petter Reinholdtsen wrote an informative post on how to make a bootable USB stick image from an ISO file [9]. Apparently Lenovo provides ISO images to update laptops that don’t have DVD drives. :(

Barry Gander wrote an interesting article about the fall of Rome and the decline of the US [10]. It’s a great concern that the US might fail in the same way as Rome.

Ethan Siegel wrote an interesting article about Iapetus, a moon of Saturn that is one of the strangest objects in the solar system [11].

Cory Doctorow’s article Revenge of the Chickenized Reverse-Centaurs has some good insights into the horrible things that companies like Amazon are doing to their employees and how we can correct that [12].

Charles Stross wrote an insightful blog post about Billionaires [13]. They can’t do much for themselves with the extra money beyond about $10m or $100m (EG Steve Jobs was unable to extend his own life much when he had cancer) and their money is trivial when compared to the global economy. They are however effective parasites capable of performing great damage to the country that hosts them.

Cory Doctorow has an interesting article about how John Deere is being evil again [14]. This time with potentially catastrophic results.

[1] https://tinyurl.com/yeppy78q
[2] https://tinyurl.com/28yt5wbg
[3] https://onezero.medium.com/rubber-hoses-fd685385dcd4
[4] https://tinyurl.com/2ztqaw9a
[5] https://tinyurl.com/2kv68veo
[6] https://en.culturess.com/view/?id=santiago-genoves-experiment-cul
[7] https://mjg59.dreamwidth.org/59479.html
[8] https://tinyurl.com/yy8pyg65
[9] https://tinyurl.com/2qr9evgb
[10] https://tinyurl.com/2ngytzuh
[11] https://tinyurl.com/2qjffrt3
[12] https://tinyurl.com/2ote6mw7
[13] https://tinyurl.com/yxe75yel
[14] https://tinyurl.com/y23lbw2n

Links September 2022

Tony Kern wrote an insightful document about the crash of a B-52 at Fairchild air base in 1994 as a case study of failed leadership [1].

Cory Doctorow wrote an insightful medium article “We Should Not Endure a King” describing the case for anti-trust laws [2]. We need them badly.

Insightful Guardian article about the way reasonable responses to the bad situations people are in are diagnosed as mental health problems [3]. Providing better mental healthcare is good, but the government should also work on poverty etc.

Cory Doctorow wrote an insightful Locus article about some of the issues that have to be dealt with in applying anti-trust legislation to tech companies [4]. We really need this to be done.

Ars Technica has an interesting article about Stable Diffusion, an open source ML system for generating images [5], the results that it can produce are very impressive. One interesting thing is that the license has a set of conditions for usage which precludes exploiting or harming minors or generating false information [6]. This means it will need to go in the non-free section of Debian at best.

Dan Wang wrote an interesting article on optimism as human capital [7] which covers the reasons that people feel inspired to create things.

[1] https://tinyurl.com/29bexyah
[2] https://tinyurl.com/2g632oah
[3] https://tinyurl.com/2zjkf45t
[4] https://tinyurl.com/2f8pqq55
[5] https://tinyurl.com/2jr94rm2
[6] https://tinyurl.com/2ev8vwfb
[7] https://danwang.co/definite-optimism-as-human-capital/

Storing Local Secrets

In the operation of a normal Linux system there are many secrets stored on behalf of a user. Wifi passwords, passwords from web sites, etc. Ideally you want them to be quickly and conveniently accessible to the rightful user but also be as difficult as possible for hostile parties to access.

The solution in GNOME and KDE is to have a wallet that is encrypted to store such passwords, the idea is that if a hostile party gets access to a PC that doesn’t use full disk encryption then the secrets will be protected. This is an OK feature. In early versions it required entering a password every time you logged in. The current default mode of operation is to have the login password used to decrypt the wallet which is very convenient.

The problem is the case where the user login password has a scope larger than the local PC, EG a domain login password for Active Directory, Kerberos, or similar systems. In such a case if an attacker gets the encrypted wallet that could facilitate a brute force attack on the password used for domain logins.

I think that a better option for this would be to store wallets in a directory that the user can’t access directly, EG a mode 1770 directory with group “wallet”. Then when logging in a PAM process running as root could open the wallet and pass a file handle to a process running in the context of the user. For access apart from login there could be SETGID programs to manage it which could require authenticating the user’s password before any operation that exports the data so that a vulnerability in a web browser or other Internet facing program can’t just grab the file contents.

Storing the data in a file that needs a SETGID or root owned process to access it doesn’t preclude the possibility of encrypting that file. The same encryption options would be available including encrypting with the login password and unlocking at login time via PAM. The difference is that a brute force attack to discover the login password would first require breaking the security of one of those SETGID programs to get access to the raw data – direct attacks by running the wallet open command repeatedly could be managed by the usual rate limiting mechanisms and logging in the system logs.

The same methods could be used for protecting the secret keys for GPG and SSH which by default are readable by all processes running in the user context and encrypted with a passphrase.

The next issue to consider is where to store such an restricted directory for wallets. Under the user home directory would give the advantage of having the same secrets operate over a network filesystem and not need anything special in backup configuration. Under /var/lib would give the advantage of better isolation from all the less secret (in a cryptographic sense) data in the user home directories.

What do you think?

Links Aug 2022

Armor is an interesting technology from Manchester University for stopping rowhammer attacks on DRAM [1]. Unfortunately “armor” is a term used for DRAM that looks fancy for ricers so finding out whether it’s used in production is difficult.

The Reckless Limitless Scope of Web Browsers is an insightful analysis of the size of web specs and why it’s impossible to implement them properly [2].

Framework is a company that makes laptop kits you can assemble and upgrade, interesting concept [3]. I’ll keep buying second hand laptops for less than $400 but if I wanted to spend $1000 then I’d consider one of these.

FS has an insightful article about why unstructured job interviews (IE the vast majority of job interviews) give a bad result [4].

How a child killer inspired Ayn Rand and indirectly conservatives all around the world [5]. Ayn Rand’s love of a notoriously sadistic child killer is well known, but this article has a better discussion of it than most.

60 Minutes had an interesting article on “Foreign Accent Syndrome” where people suddenly sound like they are from another country [6]. 18 minute video but worth watching. Most Autistic people have experience of people claiming that they must be from another country because of the way they speak. Having differences in brain function lead to differences in perceived accent is nothing new.

The IEEE has an interesting article about the creation of the i860, the first million-transistor chip [7].

The Game of Trust is an interactive web site demonstrating the game theory behind trusting other people [8].

Here’s a choose your own adventure game in Twitter (Nitter is a non-tracking proxy for Twitter) [9], can you get your pawn elected Emperor of the Holy Roman Empire?

[1] https://tinyurl.com/2lk9xr7q
[2] https://tinyurl.com/2njkc22w
[3] https://frame.work/
[4] https://fs.blog/job-interviews
[5] https://tinyurl.com/2co3l83n
[6] https://tinyurl.com/yzpsvfof
[7] https://spectrum.ieee.org/intel-i860
[8] https://ncase.me/trust/
[9] https://tinyurl.com/2jwbfcto

TSIG Error From SSSD

A common error when using the sssd daemon to authenticate via Active Directory on Linux seems to be:

sssd[$PID]: ; TSIG error with server: tsig verify failure

This is from sssd launching the command “nsupdate -g” to do dynamic DNS updates. It is possible to specify the DNS server in /etc/sssd/sssd.conf but that will only be used AFTER the default servers have been attempted, so it seems impossible to stop this error from happening. It doesn’t appear to do any harm as the correct server is discovered and used eventually. The commands piped to the nsupdate command will be something like:

server $SERVERIP
realm $DOMAIN
update delete $HOSTNAME.$DOMAIN. in A
update add $HOSTNAME.$DOMAIN. 3600 in A $HOSTIP
send
update delete $HOSTNAME.$DOMAIN. in AAAA
send

Links July 2022

Darren Hayes wrote an interesting article about his battle with depression and his journey to accepting being gay [1]. Savage Garden had some great songs, Affirmation is relevant to this topic.

Rorodi wrote an interesting article about the biggest crypto lending company being a Ponzi scheme [2]. One thing I find particularly noteworthy is how obviously scammy it is, even to the extent of having an ex porn star as an executive! Celsuis is now in the process of going bankrupt, 7 months after that article was published.

Quora has an interesting discussion about different type casts in C++ [3]. C style casts shouldn’t be used!

MamaMia has an interesting article about “Action Faking” which means procrastination by doing tasks marginally related to the end goal [3]. This can mean include excessive study about the topic, excessive planning for the work, and work on things that aren’t on the critical path first (EG thinking of a name for a project).

Apple has a new “Lockdown Mode” to run an iPhone in a more secure configuration [4]. It would be good if more operating systems had a feature like this.

Informative article about energy use of different organs [5]. The highest metabolic rates (in KCal/Kg/day) are for the heart and kidneys. The brain is 3rd on the list and as it’s significantly more massive than the heart and kidneys it uses more energy, however this research was done on people who were at rest.

Scientific American has an interesting article about brain energy use and exhaustion from mental effort [6]. Apparently it’s doing things that aren’t fun that cause exhaustion, mental effort that’s fun can be refreshing.

Workstations With ECC RAM

The last new PC I bought was a Dell PowerEdge T110II in 2013. That model had been out for a while and I got it for under $2000. Since then the CPI has gone up by about 20% so it’s probably about $2000 in today’s money. Currently Dell has a special on the T150 tower server (the latest replacement for the T110II) which has a G6405T CPU that isn’t even twice as fast as the i3-3220 (3746 vs 2219) in the T110II according to passmark.com (AKA cpubenchmark.net). The special price is $2600. I can’t remember the details of my choices when purchasing the T110II but I recall that CPU speed wasn’t a priority and I wanted a cheap reliable server for storage and for light desktop use. So it seems that the current entry model in the Dell T1xx server line is less than twice as fast as fast as it was in 2013 while costing about 25% more! An option is to spend an extra $989 to get a Xeon E-2378 which delivers a reasonable 18,248 in that benchmark. The upside of a T150 is that is uses buffered DDR4 ECC RAM which is pretty cheap nowadays, you can get 32G for about $120.

For systems sold as workstations (as opposed to T1xx servers that make great workstations but aren’t described as such) Dell has the Precision line. The Precision 3260 “Compact Workstation” currently starts at $1740, it has a fast CPU but takes SO-DIMMs and doesn’t come with ECC RAM. So to use it as a proper workstation you need to discard the RAM and buy DDR5 unbuffered/unregistered ECC SO-DIMMS – which don’t seem to be on sale yet. The Precision 3460 is slightly larger, slightly more expensive, and also takes SO-DIMMs. The Precision 3660 starts at $2550 and takes unbuffered DDR5 ECC RAM which is available and costs half as much as the SO-DIMM equivalent would cost (if you could even buy it), but the general trend in RAM prices is that unbuffered ECC RAM is more expensive than buffered ECC RAM. The upside to Precision workstations is that the range of CPUs available is significantly faster than for the T150.

The HP web site doesn’t offer prices on their Z workstations and is generally worse than the Dell web site in most ways.

Overall I’m disappointed in the range of workstations available now. As an aside if anyone knows of any other company selling workstations in Australia that support ECC RAM then please let me know.

DDC as a KVM Switch

With the recent resurgence in Covid19 I’ve been working from home a lot and using both my work laptop and personal PC on the same monitor. HDMI KVM switches start at $150 and I didn’t feel like buying one. So I wrote a script to change inputs on my monitor. The following script locks the session on the local machine and switches the monitor’s input to the other machine. I ran the command “ddcutil vcpinfo| grep Input” which shows that (on my monitor at least) 60 is the VCP for input. Then I ran the command “ddcutil getvcp 60” to get the current value and tried setting values sequentially to find the value for the other port.

Below is the script I’m using on one system, the other is the same but setting the different port via setvcp. The loginctl command is to lock the screen to prevent accidental keyboard or mouse input from messing anything up.

# lock the session, assumes that seat0 is the only session
loginctl lock-session $(loginctl list-sessions|grep "seat0 *$"|cut -c1-7)
# 0xf is DisplayPort, 0x11 is HDMI-1
ddcutil setvcp 60 0x11

For keyboard, mouse, and speakers I’m using a USB 2.0 hub that I can switch between computers. I idly considered getting a three-pole double-throw switch (four pole switches aren’t available at my local electronic store) to switch USB 2.0 as I only need to switch 3 of the 4 wires. But for the moment just plugging the hub into different systems is enough, I only do that a couple of times a day.

etbe – Russell Coker

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USB-PD and GaN

Thinkpad X1 Carbon Gen5

Gen1

Choosing a Replacement

A Cheap? Gen5

A Cheap Gen6

Finally Working

Links November 2022

Links September 2022

Storing Local Secrets

Links Aug 2022

TSIG Error From SSSD

Links July 2022

Workstations With ECC RAM

DDC as a KVM Switch

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