The firmware & hardware has been extensively revised to better suit the Atari ST range of computers. The PCB has been revised in various places to include more parts on the bottom so that they can be supplied preassembled. It's most prominent new feature is the on-board DUALTOS ROM where the decoding is built into the PLD. You can for example have TOS206 and EMUTOS in ROM without requiring a separate dual TOS board. There have been other tweaks for better compatibility with the Atari machines such as fixing the IDE port to use a standard cable.

NOTE: Only 60MB of TTram is available as some is used for ROM shadow. Typically 60MB is free to use, the next 1MB is a "black hole" to prevent TOS from declaring it. Then ROM area and special registers. RAM could be used above that in special software but probably nothing will use it.

SEE MODIFICATIONS SECTION BELOW FOR NEW MODS AND NEW BETA FIRMARE

OTHER STUFF

EMUTOS1.4_TOS206 DUALTOS ROM - (Patched 206) October 26, 2025

Day of the tentacle (GAME)

BLTFIX1.2 - Needed in AUTO folder to fix blitter issues.

ROM SPACER - Keeps pressure on the STE536 from the top metal sheilding.

BRACKET - Adds support for the rear of the STE536.

JTAG - PLD programming header.
CDIS - CPU Cache disable (generally not used)
MMUDIS - CPU MMU disable (generally not used)

ROM HEADER:
BANK 0 - Lower ROM bank select
BANK 1 - Upper ROM bank select
512K ROM - Can use 512K OS ROM (currently not used)

JP2 - 5V power input direct from PSU - Currently with a quality PSU I have not seen any reason to connect the powre directly.

SJ3 - Middle and bottom pad must be connected to enable the default OSC.

Any other jumpers or solder pads are not to be used or connected.

REV4.7D IC10 Regulator may be missing. It was a upgraded regulator from previous builds. Part number ADM7172ACPZ-3.3-R7 / GM12046ACPZ-3.3-R7

PSU needs to output 5.20V. Otherwise it may be unstable. Generally shows as ROM copy fails, TTram fails or lockups, or random resetting etc. While the SR98 can be easily adjusted, it dtops about 0.10V when the floppy turns on. So voltage output on SR98 should be about 5.15V to compensate. (This voltage issue was also found on the DFB1X Falcon booster)

My patched TOS206 fixed cache issues with the 030 CPU which will corrupt DMA activities. It will auto copy TOS ROM to TTram in a reserved block of TTram above the 60MB mark. It will survive a warm reset but (at the time of typing) a cold boot seems to cause a "bad rom chip error", I don't know why. If you get that, power down for 10 seconds and reboot.

Cache and blitter options are available in the desktop menu. These are saved into unused bits in newdesk.inf. TTram test after STram test will also show if you don't skip STram test on powerup.

NOTE if you have a original Atari PSU such as SR98, you need to recap and alter the voltage to about 5.15V.

If you followed the previous modifications , you need to remove the long clock wire shown in THIS image. The wire which soldered onto the track needs to be removed.

Solder a 330R (1/8 watt) resistor as shown above. This is a clock termination resistor.

If you have a ~47pF capacitor there from previous mods, remove it.

EXP4 20-jan-2026 - new experimental clock switching logic - no known issues. ASCI port untested.