Advanced Settings
Table of contents
Overview
Advanced settings are available on board revision 3 (RP2350), from firmware v3.0. This page describes firmware v4.0.0; the settings marked v4.0.0 are new in firmware v4.0.0.
The board comes set up for a stock Atari ST, STE, Mega ST or Mega STE, and most people never change these settings. There are good reasons to try them, though:
- Noisy buses: adjusting the bus timing can fix crashes on a computer whose signals are not clean.
- A degraded clock: adjusting the bus timing can help a computer whose clock has drifted.
- Accelerated computers: an accelerator board changes the bus timing, and the board can be set to keep up.
The CONFIG.TXT file
The settings are in CONFIG.TXT, a plain text file in the ROMEMUL drive you see when you connect the board to your computer.
To change a setting, open the file with a text editor, change the number after its name, save the file and eject the drive. The board reads it when the drive is ejected and uses the new values from the next time the Atari starts. Lines starting with ; are notes.
This is the file firmware v4.0.0 comes with:
; SidecarTridge cartridge settings
;
; To change a setting, edit the number after its name, save this
; file and eject the ROMEMUL drive. The new settings are used from
; the next time the computer starts. Lines starting with ; are notes.
;
; Some settings only matter on one of the two boards. The file
; INFO.TXT on this drive names yours on its "Board variant" line:
; RP2350A or RP2350B.
;
; --- Timing ---------------------------------------------------------
;
; How long the cartridge waits, after the computer asks for a ROM
; address, before it reads that address. 4 suits most computers. If
; the computer shows a garbled screen, crashes, or does not start
; with a ROM that works elsewhere, try other values, one at a time:
; from 2 to 8 on the RP2350A board (lower values work as 2), from 0
; to 8 on the RP2350B board. Allowed: 0 to 19.
READ_BUS_TICKS = 4
;
; Leave at 0: the Atari ST and the Amiga do not use it.
USE_OE = 0
;
; RP2350B board only; the RP2350A board ignores these three. Each
; one makes the cartridge answer the computer a little sooner.
; Leave them at 1. Set one to 0 only to troubleshoot a computer that
; does not start. Allowed: 0 or 1.
CE_SYNC_BYPASS = 1
WRITE_ON_DRIVE = 1
DMA_HIGH_PRIORITY = 1
;
; --- Rescue ROM without the RESCUE switch --------------------------
;
; Seconds. To start the rescue ROM (named in RESCUE.TXT; normally
; the ROM switcher) without the RESCUE switch, switch the computer
; on with its RESET button held down, keep holding it for longer
; than this many seconds, then release it. A normal start is not
; delayed. 0 turns this off. Allowed: 0 to 600.
RESCUE_TIMEOUT = 0
;
; --- Speed ----------------------------------------------------------
;
; RP2350B board only: 1 allows ROMs larger than 512 KB, up to 1 MB.
; While such a ROM runs, the cartridge works at its highest speed,
; faster than its chip is rated for. With 0, a larger ROM is refused
; and the rescue ROM starts instead. The RP2350A board never runs
; ROMs larger than 512 KB, and a rescue ROM is never larger than
; 512 KB on either board. Allowed: 0 or 1.
LARGE_ROMS = 0
;
; 1 if the computer has an accelerator board or a faster bus and its
; ROMs crash or do not start: the cartridge then always works at its
; highest speed, faster than its chip is rated for. Both boards.
; Allowed: 0 or 1.
ACCELERATED_BUS = 0
A board upgraded from firmware v3.x with the update file keeps its old CONFIG.TXT, which has only READ_BUS_TICKS and USE_OE. The settings added in firmware v4.0.0 are off until they are in the file: copy the file above over yours, and set READ_BUS_TICKS and USE_OE again if you had changed them.
To see the values the board is using, press C in the SWITCHER, or run the self-test of the rescue switcher: its Configuration line lists them.
READ_BUS_TICKS
How long the board waits, after the Atari asks for a ROM address, before it reads that address. The default, 4, suits most computers.
If your Atari shows a garbled screen, crashes, or does not start with a TOS image that works elsewhere, try other values, one at a time: from 2 to 8. A computer with a noisy bus may need 6 or 8; one with an accelerator that shortens the bus cycle may work better with 2 or 3.
On this board the useful range is 2 to 19: lower values work as 2, higher values as 19.
v4.0.0
Before firmware v4.0.0, a value outside 0 to 20 went back to 4.
My experience with accelerator boards says the board won’t work on anything faster than 20-24 MHz, but I encourage you to experiment. Many other things affect the stability of an accelerated computer: the power supply, the RAM and the rest of the system. Use it at your own risk, and share your findings with the community.
USE_OE
Leave it at 0. It tells the board to wait for the ROM’s Output Enable signal before answering, which the Atari ST and the Amiga do not need: on the TOS and Kickstart carrier boards that signal is always active.
RESCUE_TIMEOUT
v4.0.0
Starts the rescue image without the RESCUE button. Set it to a number of seconds, for example 5. Then, to start the rescue switcher, switch the Atari on with its RESET button held, keep it held for longer than that, and release it. The User Guide has the steps.
A normal start is not delayed: the board only counts while the Atari is held in reset, and stops counting as soon as the Atari asks for its first ROM address.
0 turns it off, and is the default. Allowed: 0 to 600.
ACCELERATED_BUS
v4.0.0
Set it to 1 if your Atari has an accelerator board or a faster bus, and its TOS crashes or does not start. The board then always runs at its highest speed, which is faster than its chip is rated for: use it only if you need it.
0 is the default: the board runs at its normal speed.
Settings for another board
CE_SYNC_BYPASS, WRITE_ON_DRIVE, DMA_HIGH_PRIORITY and LARGE_ROMS are for the RP2350B board. Your board revision 3 is the RP2350A board, as the Board variant line of INFO.TXT says, and ignores them. Leave them as they are.
As a kind reminder, ALWAYS eject the ROMEMUL drive after changing anything on it. This makes sure the changes are saved and the board uses them.