Steven Seagal's Atari ST Web Site

Steem

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"The Score Keeper"

  New features for v3.7.  
     
 

Ghost Disks STG

 
 

Some original games saved scores on the disk. Some games saved the progress. Ghost disks allow you to keep changed sectors of a normally read-only disk image (STX, IPF...) in an apart file, thereby leaving the "original" intact.

 
     
 

 
     
 

A new option has been added in Steem to that effect.

When it's checked, and a Pasti (STX) or Caps (IPF, CTR) disk image is trying to write a sector, a new file with the same name and extension, ending with ".STG" will be created to store this sector in an efficient way (compact file).

Notice that the extension is "STG", not "STW". STW is something else (see page 2).

When later you open the same disk image, this new file will be opened as well, and when the same sectors are read by the game, the sectors of the ghost disk will be used instead of those of the STX or IPF/CTR image.

 
     
 

 
 

My motorcycle exploits saved forever.

 
     
 

 
 

One day I'm gonna beat this dude!

 
     
 

 
 

You can say who's playing by the score.

 
     
 

 
 

The table is still there one day later. Notice that to use the pasti
version, you need the manual, or the Steem patch (provided with v3.7).

 
     
   
  This is the IPF version of Sundog. Not sure it works, at least it loads.  
     
     
 

The feature hasn't been much tested as few people cared to give examples where it would be useful. Which is disappointing when you consider the feature was requested.

 
     
 

 
  Platoon (US, TOS100US) is a more intricate case. The game first formats the track then uses the "write multiple sectors" command where the sectors are 1024 bytes, and the DMA sector counter is too high.

Gulp!

It turns out however that we don't need to emulate all this to be able just to save the score. Only the multiple version of read/write sector (WD1772 commands $90, $B0) really must be handled. We do as if the sectors were regular (512 bytes), and it's fine for the game.

 
     
 

It works

 
  It's simple and it just works.
There are cases it won't handle, but let's wait for those practical cases before we introduce any complications.
 
     
     
  Specification of STG (text file)  
     
     
     
     
 

Bugfixes drive

 
  - IRQ on STEP when we're on track 0 or with no disk: Treasure Trap cr. Superior  
  - $D8/$D0: $D0 clears the IRQ only on next command: Wipe Out cr. Replicants
In fact, this game and Super Monaco GP show that the interrupt is cleared in
two steps after a $D8 command, and that the next command doesn't need to
be $D0. Official WD1772 doc is dead wrong.
- 'Pasti only for STX' option + HDD (broken 3.6.4)
 
     
 

 
 

Wipe Out

 
     
     
     
     
     
     
 

 

 
     

 

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