PlayStation 2 - MX4SIO

(Translated with www.DeepL.com/Translator (free version))

MX4SIO (Memory eXpansion For SIO) is an adapter for the PlayStation 2 that lets you connect SD cards to the memory card slot. SIO is the name of the PlayStation's interface chip. In the PlayStation 2 it is called "SIO2". The SD card does NOT replace a memory card! Since it is only an adapter and not a converter and SD cards and memory cards work similarly, but not the same, the SD card is not recognized by the console. Only specially developed homebrew software can access the SD card, although the software is currently in the development phase (see below). The hardware development is finished for now, even though further development is planned.

But why use SD cards via this adapter at all and not via USB? It may sound absurd, but the PlayStation 2's memory card port is faster. The PS2 only has USB 1.1, which means the maximum theoretical data rate is 12 Mbps (1.5 MB/s) [1]. However, this also includes overhead, which is why it's more like 1 MB/s in practice. The transfer rate at the memory card port, on the other hand, is 24 Mbps. Since the interface is not publicly specified, no statement can be made about the maximum theoretical data rate, but 1.7 MB/s have already been achieved in tests [2].

So the adapter is supposed to serve as a somewhat alternative memory expansion for the PS2, especially for slim models, in which no hard disk can be installed.

The hardware is ready, so no further changes are planned. But at the moment there is no ready MX4SIO adapter to buy. Production for private use (!) is allowed though, all data can be found in the data package. A sale of the adapter is being worked on. The revenue will then also partially flow to the software developers.
by Takeshi
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by Takeshi
The memory card interface of the PlayStation (2) is a serial interface similar to SPI. SD cards can be accessed via SPI, even though this is not usually the case. Thus, the hardware of the PS2 is largely compatible with SD cards. However, there are serious differences on the software level (MagicGate, memory structure), which is why only special software can access SD cards. The SD card is addressed by the software via the "Block Device Manager" (BDM).
by Takeshi
There is a version of the Open PS2 Loader which contains the BDM driver. With this, some games are already runnable. Depending on the game, the compatibility ranges from "doesn't start at all" to "freezes", "graphics error" and "runs perfectly".
The card is mechanical compatible with the PlayStation (one), but for now it's not clear if it will be possible to access a SD card with homebrew software.
by Takeshi
09-002-0_MX4SIO.zip (3.5 MB, 2020-08-29)
09-001-1_SIO2SD.zip (492 kB, 2020-05-02)
09-001-0_SIO2SD.zip (255 kB, 2020-05-01)
by Takeshi
test_bdm.elf (GitLab, 482 kB, 2020-05-07), (Mirror on trisaster.de)
test_bdm.elf (GitLab, 483 kB, 2020-05-23), (Mirror on trisaster.de)
test_bdm.elf (GitLab, 482 kB, 2020-06-07), (Mirror on trisaster.de)
rw_speed.elf (Dropbox of Maximus32, 884 kB, 2020-07-20), (Mirror on trisaster.de)

OPNPS2LD.ELF (Dropbox of Maximus32, 1.1 MB, 2020-07-20)
OPNPS2LD.ELF (Dropbox of Maximus32, 1.1 MB, 2020-08-06)
OPNPS2LD-v1.1.0-Beta-1627-23ba651-bdm.ZIP (PSX-Place #300 by Maximus32, 1.2 MB, 2021-01-16) (Mirror on trisaster.de)
Compatibility list for the OPL beta (TnA/Takeshi, 24 kB, 2021-02-28)
by Takeshi
by Takeshi
wisi (software developer)
Maximus32 (software developer)
Takeshi (hardware developer)
TnA/PLASTIC (tester, organization)
Anakin94 (tester)
by Takeshi
The idea and first driver development in PS2SDK existed many years before (2018 I think), but in April 2020 the project picked up again. The then still current name "SIO2SD" still collided with an Atari project. Real hardware didn't exist yet, so old memory cards were used for development, with SD card slots soldered to them with cables. In May I developed a circuit board which fits into PS2-MC-cases and can take microSD-cards and contained two LEDs.
Still in May, the further development of the board began, which should then also swallow large SD cards. Since the use of original memory card housings for mass use in the future didn't seem to be a good idea, a 3D printed housing was used completely in July and the board was no longer adapted to the dimensions of the original memory card. This also made it possible to increase the platinum thickness from 1.00 mm back to 1.55 mm, which makes the board cheaper and more easily available. In addition, it now fits into a PlayStation 1. The name has been changed to MX4SIO to avoid confusion. A transistor was added to better detect if an SD card is inserted. In July/August the board was finished, tested, is "final" for the first time and finished for the time being.
by Takeshi
by Takeshi

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