FAQ
Understanding the Difference Between MFM/RLL HDD and DREM Emulator
Can DREM Emulator replace my MFM/RLL hard drive?
Not exactly. Think of an MFM/RLL hard drive like an old-school tape recorder—it just records and plays back raw signals sent from the hard drive controller without really “understanding” what those signals mean. The DREM Emulator, on the other hand, works more like a modern MP3 player. It decodes those signals into actual data, stores them in disk image files, and then regenerates the same signals when needed. So it’s not a direct replacement, but it does the job in a more advanced way.
How do MFM/RLL hard drives store and retrieve data, and in what way does the DREM Emulator operate differently?
Imagine an MFM/RLL drive as a tape recorder. The controller sends signals (think of it like a music track), and the drive just records or plays it back without knowing what it is. It doesn’t care whether it’s storing text or an image—it just processes raw signals.
The DREM Emulator is smarter. Instead of just playing back the signals, it actually decodes them and turns them into data that’s stored in disk image files. So, when it’s time to retrieve the data, DREM recreates the exact signals the controller expects. It's like converting an old cassette recording into a high-quality digital file, which can then be played back seamlessly.
Why does this difference matter for compatibility?
The big thing with DREM is whether it can properly understand the signals coming from your specific hard drive controller. So instead of wondering whether DREM can replace your exact hard drive, what matters more is if it’s compatible with the controller your system uses.
How can I figure out which controller my system uses?
Check your system’s documentation:
Look for any information that came with your computer or system—it might mention the type or model of the hard drive controller.Look inside your system:
Open up your system and find the hard drive controller circuit board (the PCB). There should be a model or type label on it.Submit pictures for help:
If you’re unsure, take clear photos of both sides of the hard drive controller’s PCB, making sure that any labels or designators are easy to read. You can send these to the DREM support team for further help.
What if it is impossible to determine the controller type?
No worries! Even if you can’t identify the controller, you can still use the DREM Emulator. Just hook DREM up to your computer and perform a low-level format while logging the debug info. This process is described in detail in Appendix 7 of the DREM User Manual. The logs will help the DREM team analyze and configure the emulator for your system.