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The ACSI2STM is a modern hard drive replacement for the Atari ST, STE or MegaSTE. It connects to the ACSI port and can manage two SD cards simultaneously, one card with an Atari hard drive image (C:, D:, E: ...) and a second card in normal PC format (FAT32 or exFAT). This second card appears in the Atari as an additional drive and can be read and written to directly on the PC. This makes the ACSI2STM perfect for exchanging data between Atari and PC, without the need for special software.

The SD4ST+ also replaces the old ACSI hard drive, but works more simply. In its current state, it can only read flashed SD cards, i.e. cards to which a complete Atari hard drive image has been written on the PC. It does not yet recognise normal PC cards with FAT32 or exFAT. This makes it less flexible than the ACSI2STM, but just as fast and reliable.

Defective DMA chip? No problem!

I also had this experience when I bought an STE that constantly deleted all SD cards in the SD4ST! The culprit was a defective DMA chip! This caused connected hard drives, regardless of whether they were compatible with the ATARI (Megafiles) or the SD4ST, to be deleted after the first write operation. All data gone! This cannot happen to you with the ACSI2STm! It doesn't care about a defective DMA!

The decisive advantage......

of the ACSI2STM really lies in the possibility of using simple SD cards (FAT32) that you have loaded with ATARI software on your PC. I have tried cards up to 32GB, all of which worked without any problems. And the ACSI2STM can do this in two different ways. You can flash your ATARI image onto an SD card as normal, e.g. with WIN32DiskImager. I always recommend an 8GB card, which can accommodate 14 partitions of 512 MB. However, you can also use a much larger SD card, simply format it with FAT32 on your PC and create a directory called ‘acsi2stm’ (it must be called exactly that). In this directory, you store the ATARI image, which must be called ‘hd0.img’. Depending on which slots you insert the cards into, the PC card will be integrated as

• Drive L (PC-SD in Slot 1, Image in Slot2)
• Drive M (PC-SD in Slot2, Image in Slot3)
• Drive N (Image in Slot2, PC-Karte in Slot3) 

Of course, you must bear in mind that the partition occupied by the PC card will be lost in your image! This means you will have 512MB less, but this is basically irrelevant for the ATARI software.

Update the firmware!

Updating the firmware for the ACSI2STM is completely straightforward and can be done by anyone: Search for ASSETS in GITHUB . If nothing appears, click on it:

There, click on the latest version (e.g. ‘Release 5.1b’) and download the ZIP archive. After unzipping, you will find the FIRMWARE directory. The update is located there.

• Unzip the ZIP file. You only need the file acsi2stm-5.1b.ino.bin from the archive. Rename this file to firmware.bin.

• Take an empty micro SD card (formatted to FAT32) and copy only the firmware.bin file to the card.

• Insert the card into slot 0 of the ACSI2STM.

• Switch on the Atari: the device automatically recognises the file and flashes itself. During this process, the LED flashes differently than usual.

• After about 30 seconds, everything is done and the file is automatically deleted so that the update is not repeated.

• The card can be used normally again.

So, a little legal notice: I have tested these instructions and they work perfectly! I accept no liability if you destroy the firmware on the ACSI2STM! Translation of www.deepl.com!