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 HAGA - introduction

  
  HAGA is abbrev. of 'Hard disk Gaming Atari' . After some years of experience with this, I felt that it is time to make new system, which will work for all people with regular Atari machines in range 1040 ST  up to  Falcon . With all decent hard disk drivers, 1GB Falcon partitions etc. No plans to support running games from Mint, Magic, for running on CT6x and other accelerators, add-ons. Very likely it will not work well on them, so turn off if possible, or use another machine, emulator.
Features: 
  • Most of games will work with 1MB RAM min.
  • Fast loadings - with more RAM and 68030 even faster
  • Support for all game categories:  TOS calling and TOS killing ones, those running at low RAM and using TOS calls.
  • TOS version incompatibility problems solved by using  modded TOS 1.04 in high RAM
  • Solutions for specific game bugs (yes, they exist) , like 24-bit bus mode for TT .
  • Work with any decent hard disk driver (correct PUN info), 1GB Falcon partitions.
  • Exit to Desktop, gamestate savings. Later with autoincrementing filenames, up to 100 saves. Very easy and fast restoring of game pos, because savestates are TOS executables. Adding comments in savestate files possible.
  • SCRSH/simpsbvh.png Showing file number during saving state.
  • Optional autosave by pressing Desktop exit key - for case of accidental key press, or those who like it.
  • Support for configs with lot of RAM occupied - max some 1600KB on Falcon, 4MB machines.  However, expect problems with diverse third party disk caches and similar - they should be avoided.
  • 'Smooth loading' support - only with latest my hard disk drivers. Even without caches, RAMdisk, fluid load without sound interrupts and screen flashes, color changes. See video below.
  • Work from floppy too. At least those which fit on 1 floppy. If space is tight you may drop PCH image. And of course work from HxC floppy emulator. Then more space available - as it supports some high density formats not possible with real floppies. For more details: drop me mail, or ask in forum.
Gamestate savefiles (snapshots): they hold all data needed to restore complete game and machine state to same as it was in moment of pressing key for it. Size of files depends from game's RAM usage. Typically it is 513KB for games running from floppies on 512KB ST machines.  Of course, you may run savestates only in game's directory, because it uses files there.
Running savestates on different machine than on which were recorded: it is possible, except running on different base machine. So, snapshot done on Falcon will not work on ST or versus. Snapshot made on STE may work on ST, except few cases. It could be done, but is too complicated by some games, and I don't see that there is interest for it.  What is interchangeable for sure:  snapshot made on ST with some hard disk will work on another ST, with different RAM size, different hard disk, driver. It will work on Steem, Hatari too.

Falcon, TT specific: there is included a lot of support for making this machines as much as possible ST(E) compatible - like CPU speed, cache settings, bus settings - for instance 24-bit bus emul. for TT. Still, there are cases when game code must be corrected at some places - like stackframe dependant ones. Then, we have other problems - not 100% compatible video registers, timing, CPU pipeline related etc. All in all, in some cases making game to work on Falcon, TT may be pretty time consuming.
For now, only running from ST compatible resolutions is supported. You may start from some other, but exit to Desktop will be not OK.  I do not plan support for non-ST resolution start. Partially because we have some nice games working in ST high res (too) . It means that if you start from ST low or ST med mode, it will run in color. If start from ST monochrome mode it will run in mono, 640x400 mode. All it on same (VGA) monitor !

Currently this is under development, and not much games are done with HAGA. I expect that in max 2-3 months it will be finished, and lot of games will use it.
Significant progress is made in first month. Check adaptation DL page for new releases.

Some technical details, in deeper look:
There is number of specific tasks  needed by hard disk running of old, floppy games. Like HW test, config, installing modded TOS in RAM, Desktop Exit, saving gamestates etc. So, idea of library file, containing code and data for them is normal. It helps to have shorter launcher and statesave files, easier making of launchers, and easier updating. + saves space on hard disks - such files are called often shared files. Placing them in specific path allows that we need HAGA and other library files only in 1-1 copy on whole hard disk, for many-many games.
Depending on used hard disk driver, available RAM, CPU  there are diverse ways of accessing data on hard disk. Main problem by hard disk access is RAM conflict. TOS workspace, hard disk drivers are tied to lower RAM area. But most of games too. To resolve this, we can place modded TOS and hard disk driver in High RAM, but it is not simple, especially with usual hard disk drivers, which are not relocatible. But that way is the fastest.  Another way is to swap by every disk access request of game      low RAM area, where game is with high RAM area, where TOS and hard disk driver are saved before game start, and swap back both after finished disk access. + need to deal with MFP, interrupts, etc. All it may be time consuming, and slow in case of accessing many short data chunks, files. Fortunately, by TT and Falcon we can use PMMU for very fast virtual RAM area swap - in microseconds.  Similar is not possible on ST(E), only with HW add-on, which can swap RAM areas if placed between MMU chip and RAM. So, only for electronics.

Smooth loading:  TOS killing games use own code for floppy access. While doing it may play  music, updating  screen palette (many games have more than 16 colors at once on screen thanx to changing palette at concrete screen position). It is beause floppy operates via DMA chip.  But by usual hard disk access from such games, we need to activate TOS and hard disk drivers, what requires disabling all game's interrupts, MFP usage etc. So, by disk access music will stop, screen may flash,, flicker. And if it is combined with slow RAM swapping it may be not nice.
Good solution against it is usage of RAMdisk. But it is not always avaliable, especially on 1MB machines.
Still, 'nice loading' is possible, even with little RAM - if we have special hard disk driver, which is not MFP timer dependant, is relocatible (latest version uses PP hard disk driver and buffers in TOS save space - 40KB RAM saved !) ,  + specially modded TOS, which can run in High RAM, and it's workspace is in high RAM too. + some tricks with interrupts, MFP.  Then may perform hard disk access without stopping game's interrupts responsible for music playback control and colors on screen. So, will have nice loadings even with 1MB machines. See video below.  All it needs careful design of hard disk driver, modded TOS + some special care with games - must disable all DMA chip accessings for instance.



Video above shows 2 loading ways. Difference is best visible by loadings right before start of play. Pos. 37sec-43 sec is loading with RAMswap and system suitable for any hard disk driver. Pos. 1m51sec-1m56sec is with special hard disk driver, which allows game interrupts to work normally.  Not much faster (except in case of many short loadings), but no flashes and audio freezes.


RAM  usage, layout for different configs, max allocated RAM sizes:

With my older system one of problems for many people was need to decrease allocated RAM - because it was made for economic RAM usage.
HAGA is more flexible in this, and here is detailed RAM usage description, and max allocated RAM sizes for diverse configs:

Usual way in this is to fill RAM from top towards bottom (while TOS does exactly opposite, as is known). So, we will have more-less workspace in middle of RAM. What is used for launcher self, RAMdisks, caches etc.
By HAGA it is little more complicated, because 68030 PMMU swapping system, where pages can not be at any RAM pos.

1040 ST(E):  
Game:  512KB
Workspace: 200KB or 290KB if no GOS used. Usually used for read-ahead cache - faster loadings.
GOS4 or 5:  90KB
TOS save:  max  ~180KB - Enough for TOS 2.06 and hard disk driver using 60KB . Of course no ACCs etc.
HAGA:  top 32KB .
Total 1MB .
Max allocated RAM by hard disk driver and other is about 70KB - with T2.06. Little more by older TOS versions.

ST(E) with 2MB (or 2.5), 512KB games
Game:  512KB
Workspace: Up to 400KB. Usually used for read-ahead cache - faster loadings.
GOS4 or 5:  90KB
TOS save:  max  512KB.
HAGA:  top 32KB .
Total 2MB .
Max allocated RAM by hard disk driver and other is about 300KB .

ST(E) with 2MB (or 2.5), 1MB games
Game:  1024KB
Workspace: Up to 200KB. Usually used for read-ahead cache - faster loadings.
GOS4 or 5:  90KB
TOS save:  max  ~300KB .
HAGA:  top 32KB .
Total 2MB .
Max allocated RAM by hard disk driver and other is about 180KB .

TT with 2MB ST RAM, 512KB games
Game:  512KB
Workspace: Up to 370KB + opt. 512KB. Usually used for read-ahead cache - faster loadings.
GOS4 or 5:  90KB
TOS save:  512KB - always at 1MB-1.5MB space.
HAGA:  top 32KB .
Total 2MB .
Max allocated RAM by hard disk driver and other is about 800KB .

TT with 2MB ST RAM, 1MB games - not supported currently

ST(E) with 4MB, 512K games
Game:  512KB
Workspace: Up to ~2300KB. Usually used for read-ahead cache - faster loadings.
GOS4 or 5:  90KB
TOS save:  max  512KB .
HAGA:  top 32KB .
Total 4MB .
Max allocated RAM by hard disk driver and other is about 1400KB .


ST(E) with 4MB, 1MB games
Game:  1024KB
Workspace: Up to ~1800KB. Usually used for read-ahead cache - faster loadings.
GOS4 or 5:  90KB
TOS save:  max  1024KB .
HAGA:  top 32KB .
Total 4MB .
Max allocated RAM by hard disk driver and other is about 1400KB .

TT, Falcon with 4MB+, 512K or 1MB games
Game:  512KB-1MB
Workspace: Up to ~950KB. Usually used for read-ahead cache - faster loadings.
GOS4 or 5:  90KB
TOS save:  1MB. Always at 2MB-3MB space.
HAGA:  top 32KB .
Total 4MB .
Max allocated RAM by hard disk driver and other is about 1300KB .

As is visible, there are several schemas. People with 4MB machines should have no problems at all.
I don't know about 2MB TT users - likely not much of them playing games, so support is only for 512K games currently. 2MB ST(E) owners should have no problems too - assuming that hard disk driver installers will not set much RAM usage, and users will not install RAM eating ACCs and similar.
1MB machines can run only 512KB games (it means games running from floppy on 512KB machines) from hard disks, of course. And must take care about low RAM usage by drivers. Only minimal resident SW allowed.

    P. Putnik, Jan- Febr.  2012.