The Commodore 64 will always have a special place in my setup. As a kid I cut my teeth on an original breadbin 64. I have so many fond memories of spending weekend evenings playing Wasteland or California Games as a kid. Still to this day I use my 64. Games, bbsing and the odd bit of code keep me disconnected from the cesspool that has become the internet.
The main storage method for the 64 was the "ahead of its time" floppy drive, the 1541. This drive had a CPU, its own built-in operating system and was built like a tank.
The problem with floppy disks as a storage medium (at least one of the major ones) is their shelf life. They aren't really made for "archival" purposes. 30 years later and a lot of them fail.
Enter the SD card. Now SD card based solutions for the Commodore 8 bit family of computers isn't something new. The Tapeduino and the super simple CBM Tape Pi, which acts as a good old tape drive and the SD2IEC and the uIEC/SD which try to mimic 1541 drives are just a few that come to mind.
These options are fine for quick tasks: loading disks, making backup copies of personal disks or copying disk images to real floppies. What they aren't good at is trying to run any program that requires the 6502, either of the 6522 VIAs, or the operating system that is inside a real Commodore floppy drive like the 1541, 1571 or the 1581.
On a side note: the Raspberry Pi recently took the title of the world's best selling home computer, a title that was held by the Commodore 64 until just recently. Call it karma, but you can now use a Raspberry Pi to emulate a real-time, cycle exact Commodore floppy drive.
The Pi1541 is a 100% accurate emulation of the 6502 and two 6522 VIAs found inside the Commodore 1541 disk drive. It runs the same code, fast loaders, demos and copy protected disk images as the original drive does.
At the very minimum, apart from a Raspberry Pi 3, all you need are a few transistors and a six pin DIN cable to build your own Pi1541. If you aren't comfortable soldering and working with electronics, there are plenty of PiHats on the market that not only include all of the needed circuitry, but also include some addons like an OLED screen, push buttons and a female 6 pin DIN jack.
I've been using the Pi1541 for almost a year now as the main drive on my 64. I love the unit so much that I have 3 of them.
The first one was a unit I breadboarded shortly after I stumbled on the project. I then upgraded to a pre-made PiHat from Corei64 which gave me all the bells and whistles like the buttons and OLED screen.
My latest addition is from Ebay seller despegatop; a true work of art the fits right in next to my Commodore 64.
This really is a slick product modelled after a real 1541. The micro SD card card slides right into the front where the real floppy would go. Red and green LEDs for drive activity and power. A built in speaker that emulates the 1541 drive grinding sounds. A Commodore chicken head logo moulded into the top of the case. It even comes with the Commodore label complete with rainbow stripes and a stylized 1541 logo.
You get all the needed hardware to affix your Pi to the hat and case as well as a detailed instruction sheet for assembly and operation.
You get your standard Pi1541 fare as well. A 1" x 0.5" OLED screen and 5 navigation/operation buttons. When you first turn on the device it loads into SD2IEC mode which allows you to browse through the disk images you have stored on the SD card. Once you select an image, it flips over to full 1541 emulation. As far as your 64 is concerned, it's talking to a real 1541.
To be honest, this unit is the "Cadillac" of Pi1541s. It is slick and polished, but it does no more or less that the first breadboarded solution I created a year ago. Regardless if you want to spend the money on this professional looking solution or if you are happy with a breadboard and some wires, if you are a Commodore 64 fan, the Pi1541 is for you.