The Decromancer

Rizzing up the DECromancer MFM Emulator

Joan Touzet — Fri, 24 Oct 2025 21:11:00 GMT

Our Revision D MFM Emulators come with an upgrade already present on our QBone boards: peripheral expansion connectors.

The tiny JST SH (1mm spacing) connector is compatible with all Qwiic and Stemma QT devices. With literally hundreds of devices out there, this is the fastest and cheapest way to add physical interfaces to the emulator.

We used a SparkFun Qwiic joystick and a SparkFun Qwiic Alphanumeric Display in purple for this little demo, written entirely in a short shell script. Press the button and the text MFME appears. Check the comments in the script for further details. It would not be difficult to mount the display and joystick as a way to display more information about the currently loaded image, or reconfigure options and start/stop/restart the emulator.

You can also use the 18-pin FPC flat-cable connector with most Adafruit "EYESPI" displays. However, you must use an A-A (top on both sides) cable. Do not use the Adafruit A-B cable (connectors "flipped" on opposite ends) when connecting displays. We have tested and recommend the GCT 05-18-A-0127-A-4-06-4-T 5 inch cable available for under CAD$2.

This demo video uses that cable and an Adafruit 2.8" TFT LCD with capacitive touch. It manages full-screen video playback, though it is running without emulation running at the same time. We don't expect you want to display full-screen video during emulation, but you should be able to provide a nice menu and touch-based interface for control and feedback if that strikes your fancy.

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Please note that our earlier Rev D boards have an error in layout that requires cutting a trace. If your Rev D emulator has the 2D square barcode on the back, and a silkscreened serial number, you don't need this fix. Otherwise, cut the angled trace on the back side near the EYESPI connector to field-patch your MFM emulator:

The PCB is only two-layer, so don't worry about cutting through interior traces. There aren't any.

I have held back publishing this information for a while, but I shouldn't have. Sorry about that. There's simply not enough hours in the day for me to integrate this as fully as I'd like into emulation. Hopefully the information provided is enough for those of you in the community have more time. And who knows, maybe I'll find time over the winter holidays.

Canada Post Strike: October 2025

The DECromancers — Fri, 24 Oct 2025 16:00:00 GMT

Update, 24 Oct 2025: Canada Post has resumed shipments, but with increased times. We have re-enabled Canada Post for the least expensive shipping option - but shipping times will be increased. Our flat shipment price is also available and will still go out via DHL as an alternative. There are no guarantees on delivery timelines for Canada Post. You have been warned!

Original post follows.

Unfortunately, negotiations between Canada Post and the Canadian Union of Postal Workers have broken down, with staff walking off the job.

While we hope that the Postal Service and the Union reach an agreement quickly, we currently have no alternative but to increase shipping costs. Here is the current state of affairs, broken down by shipping destination:

Canada: Canadian customers can still choose Purolator at the checkout for domestic shipping. Sadly this is about $10 more expensive than Canada Post was, but you will at least get your package with minimal delay.

United States: The only shipper we can use with our system for you right now is DHL. Shipping typically comes to $35 plus calculated pre-ship duties, as is now required. For now, this is a fixed price. Should our cost to ship to you be more than $10 higher, we will contact you to pay the remaining amount before shipping your order.

Everyone else: We also can only use DHL to ship to you right now. Shipping costs are fixed at $50, and may or may not offer the chance to pre-pay duties, depending on destination. Should our cost to ship to you be more than $10 higher, we will contact you to pay the remaining amount before shipping your order.

Just like last time, all our carriers will experience major delays while Canada Post is on strike. Even express shipments will be delayed in transit. Carriers will likely remove their on-time guarantees and offer minimal support for shipping delays. We have no control over the transit time once a shipment leaves our warehouse. There is no solution we can offer for time-sensitive orders.

We apologise for the interruption, and hope to return to normal as soon as possible.

United States Duties

The DECromancers — Tue, 02 Sep 2025 00:24:00 GMT

We've been monitoring the US tariff situation very closely over the course of 2025. Deliveries to the US were unaffected, up until August 29th. Unfortunately, as of that date, all Canada-to-US shipments must now be sent as DDP (Deliver Duty Paid).

How it used to work

Previously, all of our shipments were sent DDU (Deliver Duty Unpaid). That means we charged you for the product, and the shipping label, and the carrier picked up your shipment from our office.

Your carrier (usually, the USPS) would then determine if the package required any duties, and if necessary, contact you for payment before delivering your package.

Almost all of our orders were under $800, so they fell under the de minimis exemption ($800 since 2016; $200 since 1930) and you were charged no duty.

How it works now

As of August 29th, the US has suspended the duty-free de minimis import exemption. All shipments are now subject to duty. Exactly how much duty is constantly changing.

As of this writing, the baseline rate is 35% for most products made in Canada, with some exceptions for CUSMA-compliant items. We also sell products made in China; duties on these shipped to the US vary from 10% to as high as 70% (!)

Our shippers, including Canada Post, Purolator, and DHL, no longer accept shipments to the US that do not have pre-paid duties. This means we must collect these duties from you in the checkout process, or we cannot generate a shipping label and send the parcel to you.

You'll see the exact amount of duties charged in the checkout after you enter your shipping address and select a shipping option. Be prepared for 25-35% markup: it's not pretty.

This sucks. We hate it. If you are a US-based customer, and you hate it too, complain to your federal, state, and local representatives. Maybe this policy can be reversed.

Customers in Canada, and the rest of the world - everything remains the same. Order as always, receive product as always.

We apologise for the change, and hope to return to how things were as soon as possible.

Canada Post Strike: 2025

Joan Touzet — Wed, 21 May 2025 16:00:00 GMT

Update, October 2025: Please see our latest update

Update, Saturday, 24 May 2025: The CUPW have announced they are not going on strike for now, just refusing overtime. While this will slow down all deliveries, it means we can re-enable Canada Post shipping for now. Please be patient as your shipments may take longer than usual.

Unfortunately, the Canadian Union of Postal Workers has announced it intends to begin strike activity on Friday, May 23rd at 12:00 AM local time.

While we hope that the Postal Service and the Union reach an agreement quickly, we currently have no alternative but to suspend shipments outside of Canada immediately. This means there are no US or International shipping options at checkout right now. Canadian customers can still choose Purolator at the checkout for domestic shipping.

We are doing this today (Wednesday, May 21st, 2025) because any packages that don't leave Canada by Thursday night would get stuck in the system until the strike ends. If that happened to your order, there would be nothing we could do about it, and everyone would be unhappy.

For US and International orders, if you are placing an order greater than C$200 (such as for MFM emulators and QBones, or bulk SCSI product orders), please email us and we can quote you alternative shipping options (such as FedEx). This will be more expensive than usual, and will take an extra 1-2 business days for turnaround.

All carriers will experience major delays while Canada Post is on strike. Even express shipments will be delayed in transit. Carriers will likely remove their on-time guarantees and offer minimal support for shipping delays. We have no control over the transit time once a shipment leaves our warehouse. There is no solution we can offer for time-sensitive orders.

We apologise for the interruption, and hope to return to normal as soon as possible.

Introducing the QBone Dual

Joan Touzet — Thu, 19 Dec 2024 14:15:00 GMT

When we ran out of QBones earlier this year, I groaned loudly. I knew it was time to revisit the complaints we'd received from customers since we first started making them in 2021:

"The board is too tall with the Beaglebone installed, and runs into cards both above and below it."
"I'd like to use my peripherals with the QBone. "
"It's too wide for my dual-width QBUS backplane."
"I keep losing the jumpers."
"I can't find driver chips anymore."

That last one is me, actually. Our supply of chips and spares exhausted at the same time as when the last board went out the door. Without drivers, we weren't going to be selling any more QBones.

In 2008 Eric Smith did an analysis of alternative driver chips, and concluded the TI AM26S10 and SN75138 would be acceptable (if not perfect) replacements for the long-since obsolete DS8641 and DS3662 parts. Sadly both parts went EOL when TI decided to shut down their 150mm wafer process. (This also killed off many of their popular older RS485 parts, such as MC3486/MC3487.)

So despite Jörg (aka Joerg) Hoppe's respin of the board in 2024, it was too little too late; the last-time buy window was closed, and stock at most resellers was gone or was restricted in volume to select (read: US Governmental) purchasers only. (We tried.)

Things were looking bleak until we got lucky in Shenzhen. A retailer was willing to sell us sufficient DS3662s, but only in surface mount form. We acquired enough to make another run of QBones and/or Unibones.

That left the other issues, and sorting out how to make surface-mount driver chips swappable for failure or misuse.

After going heads down for a few months, we have the answer: the new QBone Dual.

Design Verification Test unit. Final product will look a bit different.

What's cool about the new QBone Dual? Well:

No Beaglebone. We've integrated the entire TI Sitara CPU, DDR3, and support circuitry right into QBone Dual. No surprise costs!
Fits within a standard QBus dual-wide slot. We took extra care to ensure DEC's original QBus specs were respected:
- Above: Conductive: .343" (8.71mm), Non-conductive 0.375" (9.525mm)
- Below: .063" (1.6mm)
A refined back panel. From left to right: handle (not shown), USB-A, microUSB, midplane Ethernet RJ45 connector, 10x status LEDs, User button, 4-position piano DIP switch.
All configuration via DIP switch. No more jumpers! We even printed the reference chart right on the PCB for you.
Swappable drivers on SODIMM-sized boards. Do not put DDR RAM in these! The pinout is custom to QBone Dual. Each board holds 6x DS3662 drivers. Due to extremely limited supply, we won't be selling these separately, but we will be providing an exchange service for our customers who have failed driver chips.
I2C expansion via qwiic/Stemma QT connectors. There will only be 2 of these on the final product, not 4, but here's a preview of what you can do with parts from Sparkfun or Adafruit:

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Backward compatible with existing QBone accessories. You still get 2x QBone-compatible serial ports and the 14-pin expansion port. These are now resettable 1A fuse protected, as are the I2C connectors.

First shipments of QBone Dual to you will be in January 2025. (Sorry, we were hoping to have these to you for the holidays - timing didn't quite work out.) We'll start accepting orders after the new year; the price will be slightly less than we sold QBones for.

If you'd be interested in paying more for a QBone Dual Yukon Gold collector's edition, with many of the same upgrades as last time, please get in touch. We'll start planning for those as soon as these are well into production.

Keep up with us on Bluesky at @DECromancer, and let us know how you want to use the new QBone Dual in 2025!

Canada Post Update

Joan Touzet — Tue, 17 Dec 2024 16:00:00 GMT

Update 2025-01-06: Canada Post is accepting all parcels now. Ship times are still a bit slow. Please be patient!

It has been just over a month that DECromancer has been closed, due to the Canada Post strike. As we were preparing to switch to a different shipping provider, the strike has been ended (at least, for now).

While additional strikes may occur in the future, we hope to limit their impact on our ability to fulfil orders.

We apologise for the interruption to all our current and future customers, and welcome you back to the shop today.

Please be advised that Canada Post will not start accepting parcels for shipment until Thursday, December 19th, 2024. We will not be making any new shipments until then. Further, because of the backlog, shipping times will be slow until at least January sometime. We thank you for your patience.

The DECromancers welcome you back!

Introducing GBSCSI

George Mezzomo — Wed, 27 Mar 2024 03:00:00 GMT

We sell quite a few of our ZuluSCSI offerings. However, we've heard your requests: you want a more affordable option. Maybe you don't use your vintage computer that often. Or, maybe you're on a tight budget. (We certainly are!)

To that end, we're now carrying the GBSCSI2 OSHW SCSI drive emulator. We'll continue to carry the ZuluSCSI, and both boards use the same great firmware with the ZuluSCSI project's approval.

We asked the board's designer, George Mezzomo, to talk a bit about designing the GBSCSI.

The GBSCSI 3.5" Hybrid.

Tell us a bit about yourself, George.

I started with disassembling my toys at an early age, learning how things worked, moved on to collecting computers at age 10, and then all sorts of odd stuff, anything I could buy cheap and fix to satisfy my curiosity. At some point in my early life I started doing my own PCBs with sharpie and ferrochloride, copying designs from 80s magazines, and later tried designing boards, but wasn't much good at it (due to not knowing how to use the software properly). I then went to college to become an EE (where PCB design surprisingly isn't really taught). I was dissatisfied with school and had recently lost my dad, so I really needed something to occupy myself with. A colleague (and good friend) taught me the basics of EDA, and I liked doing that so much I've decided that's what I want to do for a job.

You're the PCB designer for the Greaseweazle. How did you get involved in that project?

I had bought an Amiga 600 for peanuts, but writing disks for the Amiga from a PC involved using a parallel port cable and DOS software - clunky, from a laptop, and results were also often unreadable. Then Greaseweazle appeared, and made that much easier and convenient - I could just use a cheap Bluepill board and a USB port, from within Windows or Linux. However, STM32 fakes flooded the market, and buying a Bluepill that would work with Greaseweazle became almost impossible. I decided I could use my newly-acquired PCB design skills to create a board that bypassed the need for the Bluepill+adapter, one that would have a STM32 from a known-good source fitted to it from the factory. Then this got moved to a higher-performance variant, and, when STM32 parts became scarce during the post-pandemic supply chain crisis, the design got yet again remade to use an improved clone chip. This has now been polished and refactored into v4.1.

The Greasewewazle v4.1 USB-floppy interface.

Why make the GBSCSI ?

GBSCSI sort of appeared from the same pattern as the Greaseweazle: I wanted a cheap device - in this case, one I could order preassembled in bulk to fit all my machines that needed their failing storage replaced (and there were many of them). STM32 CPUs were impossible to buy, and people were charging insane prices for Bluepills, fake or otherwise. Thus, an ArdSCSIno-stm32 compatible PCB was lashed-up, and released as the original GBSCSI. It originally used the cheapest clone chip I could find, which wasn't very good.

This was just cheap, devoid of any polish, but fulfilled my initial needs. However, SCSI Disk Emulators have since progressed. Since I'm lazy, and a terrible programmer, I don't want to maintain my own firmware, but I like having hardware tailored to my needs. GBSCSI2 was originally going to be a buffered variant of the earlier board, also STM32 (or similar), but given the performance increase offered by devices based on the RP2040, the decision was made to target compatibility with those.

What makes the GBSCSI different?

I wanted a design that could fit all my machines, regardless of whether they used 2.5" or 3.5" disks, with a single PCB design. Ordering 25 identical boards is much more economically efficient than ordering 10 of one design, and 15 of the other. This was the original aim of the design. Other than that, it's mostly personal preference - where I want my connectors and switches placed, that sort of thing. If I make my own board, I am afforded the freedom to change those to what I consider most convenient for my use, but also what friends I talked to would want.

Any other interesting projects coming up?

I have been meaning to refresh a few old designs and get them out the door - maybe they'll get released for public consumption, once I test them. You can see my older designs on GitHub. The real fun stuff is under NDA!

Thanks again, George, for taking the time to speak with us!

Introducing ZuluSCSI

Joan Touzet — Thu, 18 Aug 2022 12:00:00 GMT

2022-11-05 Update: As of today, we've blown through our initial ZuluSCSI v1.1 supply, and now stock the updated ZuluSCSI RP2040 design. These new devices support synchronous transfer, which means read speeds have been measured up to 9.5MB/s with suitable host hardware. Yet another win for the ZuluSCSI development team! We're thrilled to be offering these for sale as of today.

Our original blog post about the ZuluSCSI is below. For more info on the history of the ZuluSCSI product line, see the manufacturer's FAQ.

The global electronics parts shortage has not spared DECromancer. Back in April of 2022, we sold the last of our SCSI2SD v5.2 stock. Despite high demand, we've not been able to meet your needs - until now.

Shortly after we ran out of stock, Rabbit Hole Computing quietly launched ZuluSCSI, a port of their SCSI2SD v6 code to the GigaDevice GD32F205 ARM processor. We watched the project with great interest. It claimed better performance than the old SCSI2SD v5.2, and has a much easier-to-use configuration: no more app, just edit the ZuluSCSI.ini file on your SD card and copy your disk or CD-ROM ISO images to the file!

The ZuluSCSI RP2040.

But we didn't want to start carrying the product until we were sure it would work for the vintage machines we support. The first good news came when Chicken Systems founder Garth Hjelte roundly endorsed the ZuluSCSI's compatibility with samplers:

ZuluSCSI works with EVERY SINGLE SAMPLER we know of (which is all of them). All Ensoniq, Akai, Akai MPC, Roland, Emu, Ensoniq, Kurzweil, Korg, Peavey, Synclavier, Fairlight, Waveframe samplers. We don't provide a list because we haven't found a sampler it DOESN'T work on.

Plus, we knew the STM32-based SCSI2SD v6 worked well in all sorts of vintage computers, including our own collection. Things were looking up. But it was time to put the ZuluSCSI to a torture test.

After chasing our tails for an hour over a bad 50-pin SCSI cable, we found the ZuluSCSI worked flawlessly in a DEC PDP-11/23 (with CMD CQD-220 controller), an original NeXT Cube (NCR 53C90-based), and even the oddball WICAT S2150.

The ZuluSCSI running inside our WICAT S2150 (and DEC VT240 terminal).

We're very pleased with the performance and ease-of-use, and are proud to open sales up through our web store.

Some quick tips from our experiences:

Use a FAT32-formatted SD card with a single, primary partition.
For a single hard drive, place your file on the card, named HD0.img.
For a CDROM image, use the name CD4.iso for SCSI ID 4.
Our WICAT needs 1024-byte sectors. Just rename the file HD00_1024.img to make it work. (The first zero is the SCSI ID, the second is the LUN.)
If you need any special options, copy the zuluscsi.ini file onto your SD card and edit.
For very long SCSI cables, or machines without SCSI terminator power, you may need to add a 4-pin Berg ("floppy") power header to the board. You can also add a jumper to let the ZuluSCSI drive power SCSI termination on the cable if you like. (We'll offer adding these headers to the boards for you prior to shipping in the near future.)

Calibrating the MFM Emulator's voltage sensor

Joan Touzet — Sun, 31 Oct 2021 21:11:00 GMT

Recently, we had a customer complain that their MFM Emulator would get stuck in a boot loop whenever they enabled automatic startup of emulation on boot (as you might like to do when permanently installing the MFM Emulator in an old computer). We've been scratching our heads as to what might have gone wrong - and finally reproduced the issue in our lab. It turned out that wo issues were at fault here:

Our most recent units (S/N 070 and newer) have a slight resistor value change, and
This particular customer's 12V line in their vintage computer was sagging at 11.6V.

When enabling the MFM Emulator's "start emulating on boot" functionality, the powerfail program is started in the background. powerfail monitors the 12V line to see if it drops below 11.5V. If so, the program exits emulation and forces a shutdown, syncing all data to the flash/USB drives attached.

The BeagleBone senses the 12V line through a simple resistor divider, divided down to about 1.4V because the BeagleBone's analog-to-digital converter can accept a maximum of 1.8V. However, in the lab, the latest unit out of assembly read the 12.00V line at 11.6V! Because of the small resistor values used, a difference of just 20 ohms accounts for this major variation in sensitivity. And for our unfortunate customer, 11.6V read 0.4V low would be well below the 11.5V threshold, forcing a reboot - and ending up in a boot loop.

The change of resistor value was forced by the global supply chain shortage in components, meaning we were unable to source one particular resistor. Unfortunately, this resistor acts as a divider on the 12V line, feeding the analog-to-digital converter on the BeagleBone, which is used to detect a power failure situation.

The great news is that users of the MFM Emulator can fix this themselves in software. Simply edit the file /etc/mfm_emu.conf and change the line

PowerFailOptions=""

PowerFailOptions="--scale 0.1213"

We've updated the pack-in letter to call out this change for anyone who may need it.

If you want to fully calibrate your unit's voltage measurement, you'll need a voltmeter. Here's how:

Power the MFM Emulator via the 4-pin Molex connector, and ssh to your MFM emulator as root.
Run the following commands:

echo cape-bone-iio > /sys/devices/bone_capemgr.*/slots

cd ~/powerfail

./powerfail --debug --powercmd true --threshold 0 --scale 0.1253
With your voltmeter, measure the voltage at the P3 (!2V) test point on the emulator.
If the printed value does not match within 0.02V of the measured value, adjust the scale value. Decreasing the scale value will increase the value measured by powerfail.

Thanks to our customer for helping us debug this issue.

QBone Part 7: Yukon Gold

Joan Touzet — Wed, 11 Aug 2021 20:00:00 GMT

Some of you noticed the easter egg in our last blog post: the yellow QBone shown in the final image gallery.

Back when we first opened our web store, selling Snark Barkers, we received a common request: "are the edge connectors on these hard gold?" For the Snark Barker, and for the regular QBone, the answer is: no, they're ENIG.

ENIG deposits a very thin layer of gold via an immersion process over the top of the standard electroless nickel plating. The gold layer's thickness varies from 0.05 - 0.23 µm, over a 2.5 - 5.0 µm thick electroless nickel layer. We like ENIG for our boards, for many reasons:

Excellent resistance to oxidation

Low contact resistance and high strength

Good through-hole plating.

Surface finish is ideal for fine-pitch ICs, as it keeps the pads square-edged and flat.

ENIG handles reflow cycles well, a process we use to attach all of our SMD components

However, when applied to an edge connector, it is thin enough that repeated insertion/removal cycles can scrape off the gold.

While we're confident that ENIG edge connectors are fine for at least 100 insertion/removal cycles, we know that some of you out there will want to use your QBone in many systems, or use them as diagnostic tools for other people's PDP-11 and VAX systems. (We also thought it'd be fun to make a premium QBone model.)

So we took the plunge and went all out with the QBone Yukon Gold edition!

Presenting the QBone Yukon Gold, for the discerning vintage computer enthusiast.

The Yukon Gold QBone sports true "hard gold" edge connector "gold fingers," at a thickness of at least 0.762 µm (30 microinch). This is comparable to most PCBs of the 1970s and 1980s, including DEC's own boards. We expect these fingers to last for thousands of insertion/removal cycles.

All pin headers and IC sockets in the Yukon Gold QBone also have 0.762 µm (30 microinch) plating.

Each Yukon Gold QBone includes 12 fully-tested DS3662 driver chips, DEC's chosen upgraded QBus driver. All Yukon Gold QBones undergo a rigorous 24 hour burn-in test, to ensure these new old stock driver chips are fully functional.

Finally, Yukon Gold QBones come with your choice of handle, including any of the premium FDM/FFF colours we offer, or the top-of-the-line resin printed handles. (That's why we don't show the handles in our pictures - your choice is riveted on before shipping.)

Due to the high cost of the gold and rarer driver chips in these units, we are offering just 10 Yukon Gold boards for sale. Once they're gone, they're gone!

Thanks for reading our QBone blog post series. We're now proud to offer both our standard QBone and the Yukon Gold edition for sale in our web shop.