DOSBox...

Curt @ Atari Museum curt at atarimuseum.com
Fri Jan 25 16:46:09 CST 2008


Jim,

   Perhaps you could assist a little bit further, since, you working on 
the DOSbox emulator.   I am looking for some old DOS based Copy 
Protection bypass tools as the Atari disks are copy protected so as not 
to be able to read the directories on the disk and/or the disk giving a 
read error.    The disks will only work if they are booted up directly 
on post and directly go into the games, they can't be f6'd or f8'd to 
break them, its very odd, so I would like to make copies of the disks so 
they don't go bad and I lose the games, but more importantly so I can 
copy the contents to a directory that I can mount through DOSbox and 
access and run the games, so your assistance on pointing me to a good 
DOS copy protection disk resource would be greatly appreciated, thanks.


Curt



Jim Leonard wrote:
> Curt @ Atari Museum wrote:
>> Quick question - can DOSbox handle older PC programs that were meant 
>> to run on old AT 8mhz speed machines?   I've got a lot of the 
>> Atarisoft IBM game titles on 5.25"s and they run insanely fast on a 
>> modern PC, I'd like to be able to run them at a properly throttled 
>> speed.
>
> Yes.  In fact, myself and a few others have done significant work 
> trying to get CGA properly emulated (composite CGA emulation is pretty 
> damn close to the original; some tweaked modes work as well).  It can 
> even boot bootable diskette images (as long as copy protection is 
> absent).
>
> The problem you may encounter with a fixed-speed game is that it is 
> very hard to dial the number of cycles per second to get a "nice" 
> 4.77MHz speed.  DOSBOX is not cycle-exact, and some things (like 
> memory operations) are *much* faster than on the real hardware.  The 
> best you can do is to run some sort of looping benchmark (a benchmark 
> that displays results repeated) and then use ctrl-f11 and ctrl-f12 to 
> dial the cycles up and down until you get what you want.  I have found 
> a cycle setting of 233 most closely emulates a 4.77MHz machine, but it 
> depends on the game as to how faithful it is to the original.
>
> To my knowledge, there are no 100% cycle-exact early PC emulators. 
> Tand-Em is very close, but a hassle to run; MESS is also close, so you 
> might want to check that as well.
>
> One thing DOSBOX can do for you is "fix" the older games.  Some older 
> games simply run too slowly on a 4.77MHz machine to be enjoyable, like 
> some 3-D titles like Vette! or Starglider 2.  For those, you can just 
> speed the machine up a little bit and try running the game again until 
> get you get a comfortable framerate.



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