The Quarky Engineer

I think I am going to have to skip the caffeine for the next few days to hand solder this SOT553 package. The entire package with 5 pins almost fits inside an 0805 pad. It makes those usb pads look huge!

Good Morning! What a fantastic Portland day! Fire in the fireplace, a thick fog that quiets the city, and a cool rain on the roof. For some people sunshine is the key, but I love these rainy days.

Thank you to everyone the happy birthday notes! Yesterday was my 50th birthday, which in a more normal year might have called for some kind of celebration, but the world has other plans! On the positive side I have made it 50 years without breaking a bone, without ever having antibiotics, serious illness, or a hospital admission. 50 more?

I decided to spend the unplanned day doing whatever crossed my mind. Descriptions in the pictures. It was a good day.

If all else fails…

It is amazing that for $50 I can have 5 copies of 4 different PCB made and shipped to me in a week.

I have made some progress in getting things in my office setup. The PC I have under the desk ( dual Xeon 20 core ) was running Windows, but I switch that to Linux and put the windows image from the machine into a VM with a GPU passthru. I was surprised at how well that went given I was restoring the windows image from a backup.. but it worked great. VirtiO devices, QXL video, and performance is pretty good.

I also have a windows gaming box down in the datacenter room and that box is sending HDMI up to a monitor here, and I also have USB going down there for keyboard/mouse/flight stick. The USB over fiber works really well, and doesn’t seem to have significant latency.

I also got the 6 upper monitors correctly connected to a 6 DP output video card in my VM server in the DC with PCI passthru to a VM as well as a second USB extension with passthru. That too worked better than I thought it would. The USB passthru required a bit of hacking since I was trying to pass through native MB USB devices, but a few ‘quirk’ flags got that done. Next up I need to work on my Grafana screens which will be displayed on these monitors.

Still more to do, but getting better every day.

You can tell a lot about someone from their electronic parts collection. I suspect I might have a few friends who could tell you the function of every item in this picture without even having to google them.

Looks like I’ll be doing some soldering over the Thanksgiving break.

I had one of these old herculus MDA video cards that had artifacts on the screen.. random characters in a few places and some random attributes. That usually means bad video memory. The ram chips were soldered on in this case, so I unsolder all of them. MT (Micron) 4264s.

I was talking to Clay on the phone and he laughed and said ‘All of the micron 4264s go bad!’. Pretty easy to replace, but I was curious which ones were bad and how they were failing.

I grabbed an Arduino and built up a quick DRAM tester. Pretty easy to do given the interface of the DRAMS, and these particular ones have 4ms refresh intervals.

Sure enough, 4 of the 8 work perfectly, and 4 of the 8 have bad bits. You can see in the scope shot a couple of bad bits during a read bank filled with ‘1’s. Most of the bad ones had 400-800 bad bits (out of 64k), and a few had 3-4k.

It was also pretty easy to measure the actual access time, given that these are 120ns chips. It measured about 60ns from CAS fall, which is right on given the spec of 80ns max.

Speaking of vintage hardware.. and vintage floppy disks. I got a device from UK called kyroflux that is a USB attached floppy controller interface. It is interesting in that it digitized the flux signals directly from the floppy interface and sends it to the PC over USB. This makes it possible to not only to read pretty much any format or protection method, but allows for more advanced software to try and recover sector information that is damaged.

I was able to get it up and running with a Fujitsu 360K floppy drive and read and write raw images from both DOS and TRSDOS floppies.

There is another tool called HxC that can build the flux patterns from an image file (that you can edit, add files etc), and that pattern can be written back to the disk.

A really useful tool if you have a stack of old floppies laying around you want to read from, especially if they have errors. Support for HD drives (1.2M ones), and of course all of the 3 /12 and 8″ formats.

It is interesting to look at the raw flux streams and see how tenuous floppy magnetic medium is. I have to admit I am surprised it worked as well as it did for so many years!