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Pass the GPU (or how I learned to love IOMMU)

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  A few years ago I moved off VMWare in the home datacentre. Like a lot of folks I have embraced KVM for most things virtual around the house, but it's only recently that I really needed to virtualise a GPU for one of the guests. It turns out there's a few little tricks to getting this right, and I thought that since it took some time to get it all working just right I should write it down.  Even if it's so I can find what I went through! This time I am using Red Hat Enterprise Linux 10.1 so my notes may be a little specific to that platform and release, but most of this should work regardless of the distribution. First things first I am going to assume that you have KVM up and running and that you're comfortable with creating and managing guests.  If not, you will need to get that done, and if you're installing from scratch don't install any GUI because it's going to make your job easier later on Before we start installing cards, make sure your firmware set...
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"G=C800:5"

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Only a few of you will understand that title, but that's OK In the dark days of the early 1980's hard drives were mysterious, largely analogue devices  If you look at image above the connections are very different to recent technologies, and the cables carried a mixture of analogue data and digital control signals. It's not super clear in the image, but the white label towards the back of the drive was a list of "bad sectors".  Literally, these were manufacturing defects on the surface of the drive where data could not be read or written reliably. Much earlier in my career, I had to guide customers through the process of installing very expensive ten and twenty megabyte hard disks into PC-XT and PC-AT style machines.  The XT style machines didn't actually understand hard disks, and relied on a BIOS extension on the controller card to do the work.  BIOS extensions were one of the most brilliant aspects of the IBM PC architecture in my opinion, but that's a...
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OpenVMS on KVM

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    I am publishing this as a service to the community, because there wasn't a clear section in the OpenVMS (X86) documentation that walks a new admin through the bring-up process for OpenVMS on KVM. I haven't attempted to duplicate the OpenVMS documentation because that would be rather silly.  Instead I have focused on the nuances of getting it running under KVM.   You can download the document here If this is of use to you, please leave me a comment.
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1200W HF Linear Amplifier from budget parts - 2

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While I'm waiting for the rest of the parts to turn up, I have started working out how to automate band-switching on the Low-Pass Filter module.  To do this, I am relying on the output of my IC-7300 transceiver to control this. If you want to skip ahead, the source code is located on my GitHub page:   https://github.com/au-chrismor/arduino7300 As noted in part 1 of this series , the IC-7300 outputs a voltage from 0 - 8V depending on the band selected.  The approximate values (from IC-7300 forums) are listed below: 630m     7.41V 160m     7.41V 80m        6.07V 60m        5.07V 40m        5.07V 30m        0.03V 20m        4.07V 17m        3.18V 15m        3.18V 12m        2.22V 10m        2.22V 6m          1.88V   My LPF has switch...
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1200W HF Linear Amplifier from budget parts - 1

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This is either going to go very well or very badly, and if I'm honest it's 50/50 right now... I was scrolling through AliExpress (who doesn't?) and I came across a listing for a 1.2KW 1.8-54MHz LDMOS amplifier for a little over $A100.  Of course for this, it doesn't include the BLF188 device ($A300 from DigiKey).   Unlike most of the other amp packages on these markets, this one is assembled except for the LDMOS device, so there's no trying to interpret the schematic only to find it has nothing to do with the PCB you have on hand.   It didn't take long and the module arrived at my local post office.  It's small, at less than 100mm x 100mm and it appears to be quite well made: My research also tells me that a multi-band Low Pass Filter is an excellent idea and fortunately the same vendor has a nice unit at about twice the price of the amplifier module.  It arrived in the same package:   At about 250mm x 200mm it's substantially bigger than the amplifier,...
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Location: Kenthurst NSW 2156, Australia
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The IDPROM contents are invalid

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  I like my old Sun machines , but they have a small weakness in their design.  The older machines use a real-time clock known as an "IDPROM".  This device, originally made by Dallas Semiconductor has RAM, Clock, Crystal and a Battery all in one package.  If you read that back, you will see the problem: "Battery" The battery has a lifetime in years, but when it goes, the machine loses everything stored in the IDPROM.  The problem is that this data includes the MAC address, Host ID, Serial Number and even system type.  Without this data, your machine won't boot; and if it does, you won't have network access in all likelihood. Now, the chip is in a socket, because Sun knew it would fail and need replacement in the field, and while some devices (M48T02 and M48T58) are still available, other common devices, especially the M48T59 are no longer available, and there aren't and pin-compatible alternatives that I can find.   There are instructions online showin...
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ImageBuilder and Terraform - Handy Hints

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This is for my benefit as much as anybody else, because it took me a while to figure things out: Most of the time when you write for AWS ImageBuilder, the docs tell you to create separate YAML files containing your components.  That's fine, but what if you want to do dynamic substitutions on path and file names?  In that case you probably want to do the definition in the HCL language.  That is, within the actual Terraform code itself. Using S3 One of the more fiddly bits is pulling things from S3 to install on your new instance.  You need to do two things: Have an IAM policy which allows access; and Write the component to do the job Writing the IAM Create a policy resource that looks something like this: resource "aws_iam_policy" "s3_policy" {     name = "s3-policy"     policy = jsonencode(       {           Version = "2012-10-17"           Statement = [         ...
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