FlashFloppy is directly compatible with [most](#unsupported-models) Gotek devices with a 34-pin header.
all of which share the SFR model prefix (eg SFR1M44-U100K,
SFRM72-U100; though not all sellers mention the model name
explicitly). Since the fixed-format (720kB vs 1.44MB) stock firmware is
being replaced, this particular distinction between Gotek models is
irrelevant: all of them can handle an almost infinite range of disk
formats with FlashFloppy installed. The most relevant differences
between Gotek models are colour, [case style](#case-styles),
and [microcontroller](#microcontroller-options).
## Case Styles
### Three-digit display
These models provide a simple numeric indication of which disk image
is currently selected. This number may not make much sense to you
unless your disk images are explicitly numbered, or assigned to
numbered slots by an image-selector tool. The display doubles as a
track-number indicator during normal disk activity. Two buttons are
used for navigating between disk images.
Note that there are some models with only a two-digit display, or even
no display at all! These models are best avoided.
### OLED display and Rotary Encoder
More recently the factory introduced an enhanced model fitted with a
128x64 OLED display and a rotary encoder. This allows disk images to
be identified by name, and rapid navigation between images by
rotating the encoder. The encoder integrates a push button for faster
image selection.
## Microcontroller Options
Gotek devices have featured three generations of MCU: STM32F105,
Artery AT32F415, and Artery AT32F435. If buying a new Gotek you are most likely
to receive one of the Artery models, and of these I *highly* recommend
the 435! You should ask the seller which MCU they supply, if it is not
made clear in the sale listing. If you already have a Gotek you can
determine the MCU by opening it and looking at the the chip, or by
running latest FlashFloppy firmware and looking at reported SRAM size
when no USB drive is inserted (on the three-digit display you will
need to press right button to see SRAM size and firmware version).
### STM32F105
The original Gotek microcontroller. A lot of online documentation, for
example describing how to flash a Gotek, assumes this chip and may not
be directly relevant to more recent models. This MCU runs at 72MHz
and has 64kB SRAM. It is enough for reliable emulation of most disk
types, including high-density HFE disk images, on a wide variety of
host systems.
Due to lack of availability, the STM32F105 has not been
used in Gotek production since early 2021.
### Artery AT32F415
Starting Spring 2021, the STM32F105 microcontroller previously used has
been replaced with Artery AT32F415 due to cost and availability.
The major disadvantage of this chip is its tiny 32kB SRAM which
makes it difficult to reliably support some operations,
such as track formatting, and writing to high-density HFE images.
Reliability of these operations will depend on USB stick performance.
Due to this limitation, I highly recommend the latest
enhanced model with AT32F**435** MCU for new purchases!
This MCU is supplied on a number of PCB types with different package sizes:
- **SFRC922D (LQFP64):** This PCB is shared with
STM32F105; You cannot tell which MCU is installed without opening
the Gotek.
- **SFRC922AT3 (LQFP48):**
This PCB is missing the usual header pins for installing a rotary
encoder; Instead the CLK/DT wires can be connected to pins PA13 (SWDIO)
and PA14 (SWCLK) on the [programming port][pport].
- **SFRKC30AT4, SFRKC30.AT4, SFRKC30.AT4.7 (LQFP64)**:
Features the new [KC30 rotary header][kc30].
- **SFRKC30AT3 (LQFP48)**: Missing the original rotary-encoder header,
but features the new [KC30 rotary header][kc30].
- **SFRKC30.AT2 (QFN32)**: Missing the original rotary-encoder header,
but features the new [KC30 rotary header][kc30].
The first revision of this board is also missing the JC jumper
location: PC interface mode can be specified only via FF.CFG.
### Artery AT32F435
Starting July 2022, the factory is supplying an enhanced MCU option:
the Artery AT32F435. This MCU runs at 288MHz and has 384kB SRAM. It is
enough for reliable operation, extensive image caching, and will allow
for a wider range of firmware features in future. The enhanced
firmware which runs on this MCU is called **FlashFloppy PLUS**
(or **FlashFloppy+**).
This MCU is currently supplied on only one PCB type:
- **SFRKC30.AT4.35 (LQFP64):** Based on the SFRKC30.AT4 described
earlier. Features the [KC30 rotary header][kc30]. The Motor signal
can be passed through to the MCU by strapping MOR on the rear jumper
block.
## Models to Avoid
- **UFA prefix** (eg UFA1M44): Emulates a USB floppy drive and hence
lacks the 34-pin header, which is replaced by a mini-USB socket.
This model is entirely incompatible with FlashFloppy.
- **DU26, TU26 suffix** (eg SFR1M44-DU26): Emulates a slimline laptop
drive, and hence has 26-pin header with integrated power, rather
than the required 34-pin header. However, see [#155][issue-155] for
users' successful modifications to run FlashFloppy on a DU26. There
is also a [recreated schematic and layout][26pingithub].
- **FDD-UDD U144K**: A Gotek variant with 34-pin header but a completely
different PCB layout with undocumented pin headers (see photo below).
I strongly recommend to avoid this model as it cannot be programmed
by the usual serial and USB methods, and it lacks convenient headers
for popular hardware additions.
However, see [#232][issue-232] for discussion of how to program this
model via JTAG, and header assignments.
- **SFRA619**: Another Gotek variant with a different PCB layout.
See [#531][issue-531] for some discussion.
## Unsupported Models
- Models containing CH32F103 chip will not work due to insufficient SRAM. See
[issue #695](https://github.com/keirf/flashfloppy/issues/695).
So far these are reported only in black case, with no display or buttons, and
PCB model SFRC922D.
[issue-155]: https://www.github.com/keirf/flashfloppy/issues/155
[issue-232]: https://www.github.com/keirf/flashfloppy/issues/232
[issue-531]: https://www.github.com/keirf/flashfloppy/issues/531
[pport]: https://raw.githubusercontent.com/wiki/keirf/flashfloppy//assets/pheader.jpg
[kc30]: Hardware-Mods#kc30-rotary-header
[26pingithub]: https://www.github.com/liveboxandy/Gotek-SFRC2DB