SD Cards

The ZX Spectrum Next boots from an SD card, and Bizmuth uses card images: one file holding what a real card holds. The firmware, NextZXOS, the machine ROMs and the programs are all on the card, not in Bizmuth, so without one the Next has nothing to run.

Slots

The Next has two card slots, and so does Bizmuth: Media ▸ SD0 and Media ▸ SD1.

Slot 0 is the boot card, drive C: to the guest. The Next looks to slot 0 for its firmware, so a card in slot 1 alone does not boot. Slot 1 is drive D:.

Each slot offers Attach, Eject, Read-Only and Scan / Fix. The SD menus are enabled only on the Next.

Attach and Eject

Media ▸ SD0 ▸ Attach takes an image: .img, .mmc or .hdf.

Attaching or ejecting a card resets the Next, as changing the card in real hardware does.

The status bar shows an indicator per slot: empty, idle, reading, writing, unsaved changes, or corrupt. Hovering over it names the file and says whether it is read-only or read-write.

Compressed images

A card image compressed with zstd or gzip, or held in a zip archive, attaches without being unpacked first. Bizmuth recognises the format from the file’s contents, not its name. A zip archive holding several files uses the largest.

A compressed image is decompressed whole into memory and is always read-only. Its decompressed size is limited to 4 GiB.

Read-only mode

Read-Only protects the file on disk. The guest can still write: the writes go to memory, and are discarded at eject or quit. The image is never changed. The status bar shows unsaved changes once the guest has written.

It suits a card image you cannot replace, a test of something destructive, or runs that must each start from the same card.

Without it, the guest’s writes go through to the file, as on a real card, and saved games and settings persist.

Command line

--sd IMAGE attaches an image to slot 0 and --sd1 IMAGE to slot 1. --sd0 is another name for --sd.

--sd-ro attaches both slots read-only for that run, whatever the slot’s setting.

bizmuth --machine next --sd next.img --sd-ro

Shared cards

Bizmuth takes an exclusive lock on the image when it opens it read-write. On macOS and Linux, a second instance opening the same card gets read-only mode and a warning, so the two do not both write to the filesystem. On Windows the second instance refuses the card, with a message naming the file as in use by another process.

On macOS and Linux, a card image the host has mounted also opens read-only, with a warning. Windows has no such check.

Scan / Fix

Media ▸ SD0 ▸ Scan / Fix checks the card’s filesystem and reports what it finds. A card that cannot be read at all can be reformatted from here; that erases it, and Bizmuth asks first.

Error messages

“SD Card Missing TBBLUE.FW”: the card has no Next firmware, so it does not boot. A data-only image is read by a Next that has booted from another card: put a bootable card in slot 0 and this one in slot 1.

“No bootable SD card”: nothing is attached to slot 0. A card in slot 1 must move to slot 0 to boot.

“SD card not found”: the configured image has been moved or deleted since it was attached.

A corrupt or unformatted card raises a warning, once per card, and shows the slot indicator as corrupt. Scan / Fix is the next step.

Card images

Help ▸ Run Setup downloads a starter card. The Spectrum Next community publishes others; Compatibility lists how 47 of them behave.