retroarch_write_ram
Write bytes to emulated memory via the CHEEVOS address space when cores lack a memory map. Fallback write tool; verify with retroarch_read_ram because the command returns no acknowledgment.
Instructions
PURPOSE: Write a byte sequence to emulated memory via the achievement (CHEEVOS) address space (WRITE_CORE_RAM). USAGE: Fallback memory-write tool — use when retroarch_write_memory returns 'no memory map defined' or the core only supports the older CHEEVOS write API. Maximum 4096 bytes per call (NCI line-length limit). To verify the write landed (this command does NOT acknowledge — see BEHAVIOR), follow up with retroarch_read_ram at the same address. To establish a rollback point first, use retroarch_save_state_current. BEHAVIOR: DESTRUCTIVE: overwrites bytes starting at address with no undo (snapshot via retroarch_save_state_current first if you need rollback). Disables RetroArch's hardcore mode for the rest of the session. FIRE-AND-FORGET: the NCI does NOT acknowledge this command — the call returns as soon as the UDP datagram is sent, with no confirmation that RetroArch received or applied it. To verify the effect, follow up with an observable tool (retroarch_get_status for run state, retroarch_read_memory / retroarch_read_ram for memory mutations, retroarch_screenshot for visual state). UDP packets to a not-listening RetroArch are silently dropped. This is the key behavioral difference vs retroarch_write_memory, which DOES return a count: write_ram has no way to report a partial write or a rejected address — the only way to verify is a follow-up retroarch_read_ram. Direct memory write — bypasses MBC/mapper/DMA semantics. Transport: RetroArch's Network Control Interface (NCI) over UDP (default 127.0.0.1:55355, requires network_cmd_enable = true in retroarch.cfg). Local input validation rejects empty arrays, > 4096 bytes, or values outside 0-255 before the UDP send.
RetroArch exposes TWO distinct memory APIs with different address spaces: • READ_CORE_MEMORY / WRITE_CORE_MEMORY (used by retroarch_read_memory / retroarch_write_memory): goes through the libretro core's system memory map. Preferred when the loaded core advertises a memory map (most modern cores do). Errors with 'no memory map defined' if the loaded core doesn't. • READ_CORE_RAM / WRITE_CORE_RAM (used by retroarch_read_ram / retroarch_write_ram): uses the achievement (CHEEVOS) address space. Works even when no core memory map is defined, but addresses follow CHEEVOS conventions, not the system bus. Use as a fallback when read_memory returns 'no memory map defined'. Both APIs depend on the loaded core's exposed mapping — addresses you used on a different core / system will NOT carry over.
RETURNS: Single line 'Wrote N bytes → ADDR_HEX (CHEEVOS, no ack)' where N is the array length you sent. The 'no ack' in the message is a reminder that RetroArch did not confirm the write.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| bytes | Yes | Byte values to write, one per element (each 0-255). Length 1-4096 (hard cap from RetroArch's NCI single-datagram size). Written sequentially from `address`. Because RetroArch does not acknowledge this command, partial / rejected writes cannot be distinguished from successful ones at the protocol level. | |
| address | Yes | Starting address in the CHEEVOS (achievements) address space — distinct from the libretro system memory map used by retroarch_write_memory. See retroarch_read_ram for address-space caveats. Bytes are written sequentially address, address+1, ... |