25 Jan
2008
25 Jan
'08
10:46 p.m.
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.