A bootable CD image with a retro game in a single tweet

Re:A bootable CD image with a retro game in a single tweet by amenghra on Tuesday July 31, 2018 @09:45PM (#17658973)

There’s a comment on the page.

For some reason, emulators (at least the ones I tried) wait 4x what real machines wait when you use BIOS int 15b 86h. You can tweak the code if you want to play at a faster speed.

There’s probably a sound explanation for this discrepancy...

[ Parent | on HN ]

Re:A bootable CD image with a retro game in a single tweet by BGZq7 on Tuesday July 31, 2018 @11:58PM (#17659527)

I can't say I entirely understand how the Elapsed Time Wait works, but testing in qemu, I was able to get it to a good speed by replacing the

  inc cl

with a

  nop
  inc dx

By opening in a hex editor, finding

  bf86 fec1

and replacing with

  bf86 9042

If you're on a very slow system, maybe just use 2 nops or a 2-byte nop.

[ Parent | on HN ]

Re:A bootable CD image with a retro game in a single tweet by exikyut on Wednesday August 01, 2018 @10:28AM (#17662773)

I couldn't find "bf86 fec1". I did however find "b486 fec1".

"bf86 9042" made it literally so fast I physically couldn't keep up. The following worked for me (w/ QEMU on old (no KVM) Pentium M), this may be too fast on newer machines:

  xxd cd.iso | sed 's/89c3 01de b486 fec1 cd15 b445/89c3 01de b486 9042 cd15 b445/' | xxd -r > cd2.iso

(Note the creation of "> cd2.iso")

[ Parent | on HN ]