Steven Seagal's Atari ST Web Site



"Steem... The ultimate frontier"

  Development screen of Steem SSE 3.9.2.  

MonSTer alt-RAM









The driver. It needs TOS 2.06.

  Normally, even the timings are right. That is, there are no DMA wait states when accessing this memory.  

  The option. The 12Mb are 4Mb ST-RAM and 8Mb alt-RAM.

You see the 14MB hack is still available (needs no driver).

  Use of this feature is limited. It was done for fun.  

Sampling Rates


  You're not dreaming, Steem now manages more sampling rates, up to 384Khz!  
  If your soundcard isn't able to deliver such high rates, Steem will settle for the maximum available.  
  This improvement was ridiculously easy to do. I'm surprised it wasn't requested before.  
  It makes a difference in some cases where the emulated PSG vibrates faster than 22Khz. It does happen, as the max frequency is 125Khz! It can cause horrible aliasing.  

  'How does it sound Dr McCoy?'  
  'Sounds like 96Khz.'  
  Now you can play Star Trek with almost correct sound.  
  Update 3.9.3  
  The YM sound emulation, when option 'C2' (Chipset 2) is checked, will now run at 2Mhz so that samples are taken at precisely the right time. An anti-aliasing filter has been added (thx Mike Perkins). This improves the sound with all sample rates (Star Trek especially).  
  With that filter, you don't really need to choose another in option Sound/Output type.  

Alternative YM2149 emulation


  Not many bragging rights on this one, this was lifted from MAME, but hacking emulations together has always been a lot of fun. Steem SSE already borrowed code for the IKBD emulation (6301), for disk drive emulation (WD1772), for some video tricks (GLUE), etc.  
  If option 'C2' (Chipset 2) is checked, an alternative, lower level YM2149 emulation based on MAME is used. Lower level in the sense that it explicitly uses chip cycles and internal counters.  
  C2 also modifies MFP emulation, but it has effect on only a few cases.  

  I did it that way because frankly, Steem's PSG emulation is hard to understand and modify. Therefore, improvements are more like hacks (eg quantize). But it is very good: some cases will sound worse with the new emulation, especially if you don't hike the sampling rate. :)  
  It's possible there are still a few bugs in our integration.  

DC offset



PSG sound (first half Steem "native", second half option 'Sampled YM2149')



DMA sound

  The sound wave is now centred on 0. DMA sound is signed, PSG sound is unsigned.  







  Triple Buffering is fullscreen-only in the D3D build. It just asks Direct3D to add one more back buffer to the chain.  
  Windowed Borderless Mode works like in those games using it. It is fake fullscreen, there is only one back buffer, but it could be more compatible.  
  You now have a choice for bit depth, if your video card allows it (32bit should be fine).  
  The fullscreen GUI should be more compatible. You can change settings while in fullscreen, but it's more dangerous. They have immediate effect.  
  Lastly, you can now run fullscreen (or windowed for that matter) on another monitor.  


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