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Category: Retro computing

Using Greaseweazle to make bootable DOS disks

Using Greaseweazle to make bootable DOS disks

Have written previously about my experiments with the very excellent Greaseweazle; but that was reading things like my old Kings Quest 5.25″ floppy disks from my modern 12th Gen Intel PC running Windows 10.

Recently I acquired some old pc hardware and put together a retro 486-DX pc. To that end, I needed to create a DOS boot disk for this old system. That meant I needed to write a 1.2mb DOS boot disk.

Previously I used some boot disk images to create an old DOS virtual machine running Windows 1.0. For that, I used a bunch of archived boot disks images from WinWorld archive.

But how do I write these little beasts?

I floundered around with greaseweezle’s command line but this guide from Tech Tangents really helped out. There’s clearly a lot more I need to learn, but this got me a bootable 5.25″ 1.2mb floppy disk. I was able to test it on 2 different drives, and both worked. So, that’s pretty sweet!

Greaseweezle command line samples

How to write DOS 6.22 image to a 5.25″ 1.2m floppy drive attached to the ribbon cable right before the cable twist:

gw write --drive b --format ibm.1200 Dos6.22-5.25.img

To write a DOS 3.30 image to a 5.25″ 360k floppy drive attached to the ribbon cable right before the twist:

gw write --drive b --format ibm.360 DOS330-360k.img
DREM – MFM/RLL hard drive and Floppy emulators

DREM – MFM/RLL hard drive and Floppy emulators

Connecting old floppy disk drives to modern hardware is not easy. Resurrecting old MFM and RLL hard drives is even harder. The primary method would simply be to get an old PC with the legacy hardware to read the hard drives. But now there’s a few soltuions.


DREM is based on the high performance FPGA platform and does not require the use of a PC for any file encoding operations. DREM is equipped with an VGA output, PS/2 keyboard input and file manager software. A user can browse the SD card and insert DSK images into virtual drives.

DREM uses DSK disk image files, which contain the raw dump of a disk. The raw image consists of a sector-by-sector binary copy of the source medium.

If you’re just looking for floppy emulation, I recommend GreaseWeazle or other solutions.

MFM Board Emulator:

Also available, but doesn’t seem quite as well baked, is the pdp8online MFM board emulator.

Early AI was more like a therapist

Early AI was more like a therapist

ELIZA was an early ‘AI’ created by MIT scientist Joseph Weizenbaum between 1964 to 1967.

He created it to explore communication between humans and machines. ELIZA simulated conversation by using very simple pattern matching and substitution that gave users an illusion of understanding – but it had no representation that could be considered really understanding what was being said by either party. Something you can easily discover by playing with it for a few minutes.

Fast forward to 1991, and Creative Labs was having amazing success with their SoundBlaster add-on sound cards. On the driver disks that came with the SoundBlaster, there were programs showing off different capabilities. One of these capabilities was voice generation. To show off the ability to voice synthesize text, Creative Labs included a little program called Dr. Sbaitso (SoundBlaster Acting Intelligent Text-to-Speech Operator).

You interacted with it like a pseudo-therapist; but you can clearly see the connections and similar pattern/substitution methods that Eliza used. I remember being wowed by it when I played with it for the first time – and experimented for hours with it. It quickly shows its limitations, but the speech synthesis was very good for the time.

It doesn’t hold the test of time, but it is pretty neat and you can even check it out here:

ISA over USB

ISA over USB

Plugging in old ISA cards is something that hasn’t really been possible since 80486 days. This makes plugging in cool things like Sound Blaster, Adlib, Monster3D and other ISA cards pretty much impossible for modern computers. It also means things like attaching 5.25″ floppy drives and old MFM/RLL drives are also off the table. Well, maybe. 🙂

There have been a few efforts to enabling plugging in ISA boards to modern pc.

  • dISAppointment that I wrote about before is a USB plugin that exposes an ISA interface.
ISA buses on a modern PC?

ISA buses on a modern PC?

Welcome to dISAppointment! Well, it has been disappointment for anyone wanting to use old retro sound cards or attach 5.25″ floppy drives or MFM/RLL hard drives in modern computers. They all relied on ISA controllers, which have not been supported for over a decade now. But is that about to change?

I recently read about this really clever hacker’s adapter.  TheRasteri found he could still access the ISA bus lurking latently in modern computers through the Low Pin Count (LPC) bus which is exposed on the TPM port in many modern motherboards. He created a hardware interface board that connects to the TPM port, exposes an actual ISA slot.

He plugged in a Sound Blaster card via the adapter – and voila! It worked.

More details on his YouTube site, or you can follow the active development thread on Vogons. No word yet if he’s producing any for purchase; but he does want to open source the work and wants to see if he can partner with PCBWay to develop them.

I for one would absolutely buy a few of them.


Fintek makes the F85526 PCI Express to ISA Bridge IC.

  • PCI Express base spec 1.1 compliant
  • Fully ISA bridge support except bus master

It seems promising, but it is unclear if anyone has built a functioning device around the chip. Vogons even discussed it on their thread that also mentioned the dISAppointement ISA device.

New Old Sound cards

New Old Sound cards

Retro gaming has a solid community – even in the PC world. Prices of old hardware keeps going up as supply of working components goes down as time goes on. But would you be surprised to hear that people are out there making new components for these old machines? I already mentioned the recreated Covox Speech Thing, but there are even re-creations of Adlib, SoundBlaster, and other early sound cards. Enter the Orpheus ISA 16 sound card that can emulate just about any 90’s era sound card perfectly.

Dreamblaster available for purchase here:

Update: There’s other makers of clone cards too:

IBM PC Convertible

IBM PC Convertible

My very first computer was a TSR-80. I learned to first code out of necessity – you had to type in all the programs you wanted to play. My dad then purchased one of these wonderful beauties: The IBM PC 5140 Convertible.

Art Institute of Chicago

The computer was a miniaturized IBM XT 8088 system with only 2 floppy drives and no hard drive. Still, it was a huge step up with the ability to save and load programs from floppy disks.

I love that people try to preserve the history of these wonderful old machines – and you can find everything about the system including original boot disks, specs, and configurations. There also appear to be copies of the original boot disk and ROM set that work on MAME.

Parallel Sound from the Past

Parallel Sound from the Past

Back in the 90’s, computer audio devices were really limited. If you were relatively rich, you could afford a $150 Sound Blaster, or maybe a $75 Adlib. If not, you were limited to the very humble PC speaker. It turns out, however, there was one other option that didn’t get a lot of visibility.

The Covox Speech Thing (and a similar device called the Disney Sound Source) was an external audio device attached to the printer port and could output digitally generated sound. The device was a criminally simple 8-bit DAC created with a resistor ladder, an analogue output plug, and ran off simple digital signals from the printer port of the PC. How simple was it? So simple you can easily make it yourself.

Necroware does a great job covering the device, how to make your own, and gives you a full tour of the device as well as 90’s software you can use with it. Most notably, Tracker software which gave me tons of fond memories.

Update 02/2024:

Serdashop has the Covox compatible CVX4 Vogons Tuning Edition for €20. Now on it’s 4th and final version – CVX4 uses very high precision 0.1% all same value resistors, and a reverse engineered schematic (based on a real original covox). Other DIY clones use 1% or 5% resistors. Probably one of the best versions out there.


8″ Floppy drive

8″ Floppy drive

8″ floppy drives are the earliest form of floppy drives connected to early minicomputers. By the time of personal computers, 8″ floppy drives had been replaced with 5.25″ floppy drives. But those 5.25″ (and later drives) were still often based on the Shugard interface.
Adrian’s Digital Basement shows how he hooked up an 8″ floppy drive from a TSR-80 Model II to a 386SX computer – and gets it to boot! This is almost certainly something I want to try some day.