************************************************************************* * * * Backward, the ST emulator for FALCON O3O * * * ************************************************************************* PRELIMINARY NOTE : THIS IS CERTAINLY THE LAST FREEWARE VERSION OF BACKWARD. The next one will be Shareware. See chapter XIII for further information. -------- |V 1.43| -------- Summary : I) Introduction. II) Inventory. III) How to run Backward. IV) Backward's options. V) Tips. VI) Notes. VII) Technical explaination. VIII) Future improvements. IX) Address. X) Backward history. XI) Thanks. XII) Bugs report. XIII) BACKWARD II. ----------------- I) INTRODUCTION : ----------------- Since most of FALCON's owners are former ST's owners (and sometimes still ones, like me), they want their ST games to run on the FALCON. Yes, but if the GEM compatibility is good enough for as much as 90% GEM programms, hardware differences prevent about 75% games to work. That's why I created Backward. It is supposed to handle hardware differences so that good old games can still run. So far I tested it, it has offered me something like 70% compatibility. I hope you enjoy it as much as I do. --------------- II) INVENTORY : --------------- With the backward package file you must found : - READ_ME.TXT file, this one. - BACKWARD.PRG the program itself. - BACKWARD.RSC its ressource file. - CORONER.PRG the error analyst. -------------------------- III) HOW TO RUN BACKWARD : -------------------------- First, you'll have to run it on a FALCON with at least 4 Megs (simple no ?). Use a video mode that offers at least 16 colors. Double click on BACKWARD.PRG. You reach than a dialog box with three choices : - Information : Click on it and you'll see. - Set Up : Access to the configuration's dialog box. - Quit : Leave Backward. Click on Set Up to choose configuration (it will be explained later in this text) then choose a boot mode : - Boot now : Run immediatly a ST disk. - Set up now : Configure Falcon with curent choices. - Quit : Back to first box. If you select [Set up now] then [Quit], your Falcon will be configured accordingly to the options selected. If you select [Boot now], an alert box will give a last chance to refuse. REMOVE now ANY DISK which stands in the floppy DRIVE. If you continue onward, your FALCON will reboot. The ATARI logo will appear after a few seconds. Then your drive led will flash once, you have now to keep pressed ALTERNATE until the BACKWARD infos come on screen. Backward tells you the options selected and the operations it has undertaken. You can now INSERT YOUR DISK. Press a key. That's all. ----------------------- IV) BACKWARDS OPTIONS : ----------------------- This dialog box allows you to alter the FALCON set up. Feel free to try as many configuration as you want when attempting to run a programm. Each option will now be explained with advice to know when it have to be selected. - 68O3O Frequency : This option allows you to slow down the microprocessor down to 8 Mhz. It should be use when games run too fast, or for some disk protections that refuse to run. NOTE : this option has little effect on compatibility, so keep your 68O3O at 16 Mhz and enjoy light speed ! - Blitter Frequency : This option allows you to alter Blitter Frequency. I don't think it changes anything for compatibility, but it offers you another way to slow down your computer. - Instruction Cache : With this option you can turn Instruction Cache off. This a great incompatibility cause for demos and disk protection. But it seems that some FALCON TOS turn this cache on whatever you do ! - Speaker : With this you can turn the internal speaker on/off ( I must admit I have decided to unplugged it). - Ram Size : I don't think you'll need a lot of explaination for this one. - DMA sound interrupt : This should select Timer A pin or MFP input port 7 pin for sound interrupt.If you haven't any sound with a program or the sound begin then stop, try alter this option. - Bus error : This is the most important option I think. Due to hardware differences beteween ST and FALCON, access to the ST sound processor (YM 2149) may cause Bus error. So you can : - Left : don't do anything when it happens. - Corr. : this is the best handling mode so far. When it's selected, Backward will attempt to modify programs which cause errors. May doesn't work with some programs. - Simul. : correct the access to the YM2149, the middle choice but it slows everything down a bit. If your programm cause a bus error (two bombs!), it's may be because of the YM2149 access. So try the Corr. choice. If it still crashes, select Simul. - Advanced Options : This one let you access to another panel which offer more options. You don't have to use them in normal case. They are : - Move Exception Table : Normally on. Moving exception table prevents programs to disable my own error-handling routines, but it slows down the computer a little bit. If your program seems not to like it (very bugged sounds, flashing colors...) turn it off. - Emulate Line F calls : let my routine emulate some Line F calls. Use it when the programm show 11 bombs. - Move Pmmu's Tree : Well there is absolutly no reason for you to turn it off. Try it as a last solution. - Emulate St Ram Bug : Accessing a memory space where nothing was connected (no RAM, no chips' register) had no effect on a ST. It's no longer the case. Use it when your programm doesn't work. WARNING : Simul., correc. YM access won't work anymore with this option turned on, YM access will be skipped (it means disturbed digisound). - Data Cache : Normaly on, turn it off as a last solution (effects of Data Cache are uneasy to see). - Old screen address : Normally turned on, it moves the screen base to improve compatibility. No reason to change it. The last options will be implemented in the future, so are *not* useable. -------- V) TIPS: -------- In most cases you won't have to alter any option because they're already set for a good compatibility. a) Best compatibility: - Turn 68030 and Blitter to 8Mhz. - Turn both caches (instruction and data) off. - Keep pmmu's tree moved away. - Turn ST RAM Bug on (sorry that mean bad sound). - Don't care for Bus error (due to ST RAM bug). - Select 1 Meg (some old games may require 512K). - Turn Line F calls on. - Keep Old screen address on. - Try each Interrupt source for DMA sound if there's still nothing. b) How to decide configuration: - First of all, it's a game written before 1989 (before STE), and it use's digisound -> Use corrected YM Access. Then : - it's allright. Nothing to do. - The game slows too much or it stops -> try simulated access and if it's inneficient - >enable STRAM bug emulation. (you may recognize such games because they show 2 bombs). - The game has been written after 1989 and YM access options don't let the game keep running -> alter DMA sound interrupt. (such games may have a bit of music before silence, or a long whistle). - The game shows 11 bombs ->select Line F calls. - The game does *not* load itself-> turn 68030 to 8Mhz If there are still problems -> turn on ST RAM Bug. - There are still problems, try the Best Compatibility set up. ---------- VI) NOTES: ---------- - Booting with Backward will cause a cold reset (power on) on the next restart to let the Falcon reconfigure itself. - Memory Size and Bus handling have effects only if you select [Boot Now]. I may change it a day, but I'm tired. - As said before, Cache option may have no effect. - You may keep the Harddisk boot (by *not* pressing alternate key), but most of the time, harddisk is a major cause of incompatibility. ------------------------------ VII) TECHNICAL EXPLAINATIONS : ------------------------------ - Frequency configurations are made throught an undocumented address, so Backward may not work on future FALCONs. I refuse to give this address (you can still disassemble BACKWARD to see) because it's undocumented, it should be used only for emulations, no for special FXs or anything else. - Backward was written using DEVPAC ST II. - YM corrected access option uses TRAP calls (#3 to #10). - Attempts are made to recover from format error. It's luck if it works. - Disabling both caches launch a special mode : cache are kept off through PMMU. - _memtop sysvar is also modified. It's equal to _phystop on Falcon and to _v_bas_ad on ST(E). It's corrected. - they aren't bombs anymore. Falcon will reboot instead and they're is Coroner which can read my own error information structure in $380. People who undertands such things could use it to set up Backward. It has been created for my own purposes. -------------------------- VIII) FUTURE IMPROVEMENTS: -------------------------- - Improved memory configuration (use of PMMU). - Handling routines for TOS changes. This improvements will be done only if this program is satisfying.So please send donations or appreciations. Donators will be registered users and they'll get the latest version of Backward. ------------ IX) ADDRESS: ------------ You may send any donation, advice, question, bug reports etc... to this adress: Mr Cyrille Dupuydauby 53 domaine des aigles 60500 Chantilly FRANCE See you soon for V2.0. -------------------- X) BACKWARD HISTORY: -------------------- - Idea : 5 april 1993. - beta version : 10 april 1993. - V 1.00 running : 12 april 1993. - V 1.10 running : 16 april 1993. - V 1.20 running (first release) : 21 April 1993. - V 1.30 running : 28 april 1993. - V 1.32 running : 1 May 1993. - V 1.40 running : 1 May 1993 (yeah the same day, two versions). - V 1.43 running : 21 May 1993. ------------ XI) THANKS : ------------ Thanks are sent to Mathias AGOPIAN, who's article help me a lot to improve BACKWARD (essentially moving PMMU and Blitter frequency). Thanks to the Falcon for the still unused soundtrack and the uploading. -------------------- XII) BUGS REPORT : -------------------- V 1.43 ------ Bugs : - Sometimes backward crashes for no reason. Try again. - 512 Ko option will certainly never be coded. Bugs corrected : - Ym correc access code has been improved. Trap vectors are set only when they're used. - A lot of minor bugs have been corrected from the unreleased V1.41 and V1.42. - Screen address emulation was only effective after a resolution change on Desktop. It has been fixed. V 1.40 ------ Bugs : - Still nothing for 512 Ko. V 1.31 ------ Bugs: - 512 Ko Option still disabled. - Cache options were wrong till version 1.30 (flushing them instead of turning them off). It's corrected now. But the TOS seems to reset them! V 1.30 ------ Bugs: - 512 Ko Option doesn't work. It seems that the Falcon refuses to run with so little memory. Not yet corrected (if ever). Bugs corrected: - Setting DMA Sound Interrupt Timer A may had no effect in V1.20. It's corrected since V1.30. - Turning off DATA cache hadn't any effect. Corrected since V1.30 ------------------- XIII) BACKWARD II : ------------------- As mentionned before this may be the last freeware version of BACKWARD. It will be supported (i.e. unknown bugs will be corrected, but they will be no improvements, no release 1.50). Backward takes me a lot of time trying to run programs which crash the system, and I think they can't be great improvement of the compatibility rate. But Backward may still be improved, and it will be, but it won't be free. BACKWARD II will feature : - ehanced user interface, with preset set ups (like best compatibility for example) and multilingual (english, fran‡ais and maybe Deutsch). - it will be installable. You'll only have to insert your disk in drive then run Backward. There will be a configuration library. - it will be REAL-TIME configurable by pressing keys. - it will have a resident option. - it will offer you snapshot (on any game!). - memory save (for game saving). Backward II will be released in the next months during summer 93. Get registered now ! You will receive Backward II freely with a lot of configuration files.