Saving and Restoring the Machine State

A machine state is everything a machine is: the CPU, every byte of memory, the ROM, every device (sound chips, the ULA, the Next’s Copper, DMA and sprites, the Z88’s Blink and its cards), and the tape and disks inside it. Klive saves it for every machine it emulates in its own WASM cores: the ZX Spectrum 48K, 128K, +2E/+3E, the ZX Spectrum Next, the Cambridge Z88, the ZX80 and the ZX81.

Restoring a state continues exactly where it was saved, down to the T-state. Use it as a bookmark while debugging, or to hand someone a machine that shows a bug.

For the ZX Spectrum 48K/128K/+2E/+3E you can also save a standard snapshot (.szx, .z80, .sna) that other emulators open. A Klive state holds more (the tape’s exact position, the disk controller in the middle of a command) but only Klive reads it.

Saving and loading a state file

The machine must be running or paused. A running machine is paused for an instant and runs on.

File → Save Machine State…, or Save State… in the Emulator’s Machine menu, writes a .kls file.
File → Load Machine State…, or Load State…, opens one. It switches to the machine, model and configuration the state was saved on, and stops at the saved program counter, ready to debug.
Open a .kls file in the Explorer to see what it holds: the screen as it was saved, the machine, when and by which version of Klive it was saved, and its media. Its tab and its context menu can load it and run it or debug it.
Drop a .kls file onto the Emulator window to load it.
The state-save and state-load commands do the same from the command prompt.

A state file is small: from about 10 KB to a few hundred KB, whatever the machine.

Quick save and restore

Quick Save State (Ctrl+Alt+S, Cmd+Alt+S on a Mac) keeps the machine’s state in memory, without a file. Quick Restore State (Ctrl/Cmd+Alt+L) puts it back and pauses the machine. There is one slot per machine. It is emptied when you switch to another machine or model, and when Klive closes.

Klive versions

A state file is an image of the emulator’s memory, so it fits only an emulator core whose memory layout is the same. Klive records that layout in the file and checks it on load:

with the same layout, the state loads exactly;
a ZX Spectrum state saved by a version of Klive with a different layout loads from the .szx snapshot it also carries. That is nearly the same state, but it leaves out the tape’s exact position, the disk controller’s state and a few CPU details. Klive tells you when this happens;
a ZX Spectrum Next, Z88 or ZX80/81 state from a different layout cannot be loaded. The message names the Klive version that saved it.

⚠️

Treat state files as bookmarks, not archives: a Klive update can change an emulator core’s layout. Keep the program, tape or disk image that produced the state, too.

Tapes, disks and the SD card

The tape inside the machine is in the state, at its exact position.
The +3 disks are in the state too. When the state is loaded, the disks are detached from the .dsk files they came from: what the machine writes from then on is not saved to those files, because they no longer match the rewound disk. Insert a disk to attach one again.
The ZX Spectrum Next’s SD card is too big to put in the state. The state remembers which image it used and a fingerprint of its contents. Loading a state whose card has changed since asks for confirmation, because the file system on the card may no longer match what the machine remembers.
Loading a state does not change the tape or disks your project lists.

What a state does not hold

Breakpoints, watches and anything else that belongs to the project or the IDE.
With a project open, a state of another machine type is refused; close the project or open one for that machine.
The Cambridge Z88’s clock is restored as it was saved, not advanced to the current time.