Gesswein MFM Emulator Special Edition

Emulate and read/dump old MFM drives for your vintage computer

Placeholder to be replaced with photo of the MFM Emulator

Summary

We’re doing a short production run of David Gesswein’s MFM Emulator for the vintage computing community.

These are excellent emulators, capable of pretending to be 1-2 MFM disks for many old machines. We’ve had a lot of luck with them in PDP-11s, of course, but they’ll also work in a variety of minicomputers and microcomputers.

To reduce costs, we’re building 25 of these, and are including BeagleBone Green Wireless microcontrollers, pre-flashed with David’s latest emulator image.

Specs

Our “Rev C Special Edition” version has two layout modifications:

  1. The components for automatic BeagleBone shield identification have been deleted. (David doesn’t populate them on his boards, either.)
  2. In their place, footprints have been added for emulator drive activity LEDs DA0 and DA1, and their shared current-limiting resistor, R69420.

    We offer three configurations, selectable at time of purchase:
     
    • 330 ohm resistor & 2 red LEDs, on board
    • 330 ohm resistor & 2 green LEDs, on board
    • No resistor or LEDs - you supply your own. (Best choice if you want to run wires to a faceplate drive activity LED.)

The other difference between ours and David’s PCBs is that ours do not have “hard” immersion gold plating on the edge connectors. The entire board is finished with ENIG (nickel & gold). This is a significant savings (around $20 a board at these quantities!) that we feel has a minimal impact if you don’t plan on repeated mating cycles. Because of this, we recommend leaving ribbon cables connected to the fingers after first use.

Worried? Don’t be. We're probably overstating the concern. For an independent analysis, see this article about game cartridge edge connectors which shows an ENIG cartridge after 100 mate/unmate cycles. The gold is still intact.

 
3D render of the MFM Emulator Rev C Special Edition board
 

Specs for EE nerds

 
PCB
Material FR-4 TG130
Approximate Dimensions 146mm x 117mm
Layers 2
PCB Thickness 1.6mm
Copper Weight 1oz
Surface Finish ENIG-RoHS, blue solder mask
Edge connectors (gold fingers) ENIG, 45° beveled
Gerber files, schematics, etc. To be published prior to first customer shipment, under the same CC BY-SA 4.0 license as the originals. The original files are also available.
 
Components
Supercapacitors 5x AVX SCCT20B106PRB (10 Farad, -0%/+100%, 2.7V)
 
Microcontroller
Compatibility Fully compatible with BeagleBone Black
Processor AM335x 1GHz ARM Cortex-A8
Memory 512MB DDR3 RAM, 4GB 8-bit eMMC on-board flash storage
Connectivity
  • USB client for power & communications
  • USB host with 4-port hub
  • WiFi 802.11 b/g/n 2.4GHz (antennas not included)
  • Bluetooth 4.1 with BLE
 

Usage & Support

All details on use of the emulator are at David Gesswein’s website.

You’ll want to add a microSD card to hold images (either for hard disk reading or emulating), as the internal eMMC flash is slow and limited in size.

You’ll also need to source some MFM drive cables, if using the boards as drive emulators. (These might already be in your vintage computer.) Various retailers carry these for about $10 a set.

All units are tested for functionality before leaving our Toronto facility. In case your board arrives damaged, or malfunctions on first use, write us at support@decromancer.ooo.

 

Buy Now

Happy and ready to ship your order!

MFM Emulator Rev C Special Edition

Options
LED & Resistor

Orders will ship via Canada Post, with tracking and insurance.

Shipments are weekly, starting in September 2020. You will receive an email confirmation when your order ships.