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Reply 520 of 757, by VileR

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Murder on the Zinderneuf (another 1984 release) also uses mode 8 on PCjr and has the same ugly text problem, even in the original booter version. So I don't know if that by itself indicates a hack.

Out of curiosity, how 'quick' can such a hack be? The colors in PSTOP2.EXE make too much sense, and don't simply correspond to the nybble patterns used in CGA mode 6, unlike that early SCUMM sloppiness seen above. So it looks a bit more involved than that.... though admittedly that level of hacking is beyond me.

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Reply 521 of 757, by reenigne

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reenigne wrote:
NewRisingSun wrote:

I have never seen old CGA captures, so I don't know for sure about it.

I do actually have an old CGA and a capture card, so I'll have a go at creating some.

The captures are at http://www.reenigne.org/misc/old_cga_captures.zip . I used my chart.com program, so each screen shows a different graphics mode (the port 0x3d8 and port 0x3d9 values are in the top left) with different patterns in different columns and different palette register values on different rows.

Some observations:
* I adjusted the brightness and contrast so that "black" (i.e. CGA colour 0) is about 27,27,27 and "white" (CGA colour 15) is about 233,233,233. This way we can be sure that the colours aren't being clipped. Be sure to compensate for this when calibrating algorihms against these images. All other controls were left at default.

* My capture card is rather useless in the color-burst disabled modes. For one thing it doesn't have a color killer circuit, so it displays colour in these modes, but it uses the wrong color burst frequency (off by ~1.3KHz giving a pattern that repeats every 12 scanlines). It also adjusts the gain to attempt to normalize the (non-existent) color burst amplitude - i.e. turns the gain right up to maximum, causing white to be clipped, black to be much lighter than it should be and some of the colours to be wrapped. My TV has a similar extra gain in these modes but does turn off the colour. Also these modes have a vertical offset for some reason - perhaps the same gain adjustment is causing it to become confused about whether to trigger the vertical sync on the rising or falling edge.

* There's a bright scanline near the bottom in the color burst enabled images - I'm not sure why at the moment. The software isn't doing anything there.

* The capture card is set to 640x480 mode which captures two rows of pixels for each scanline. Because it uses the correct aspect ratio, that means that each CGA pixel corresponds to about 7/8 of a pixel horizontally in these images.

* There's some 7MHz signal that is not being filtered out (meaning that this capture card is using a notch filter rather than a bandpass filter for some reason). There's also some noise at about 1.7KHz giving a faint repeating pattern every 9 scanlines - not sure where that's coming from.

* Most of the colours seem to be pretty close to prediction except that the saturation is lower on the real hardware. The TV output seems a bit more saturated (compare the photos at http://www.reenigne.org/misc/cga_composite_calibration.zip), so this could be a difference between hardware and software decoders.

Unfortunately I won't be able to do any more tests on real hardware for a month or two (I'm in the process of moving and my XT is on a ship somewhere).

Reply 522 of 757, by NewRisingSun

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Having disassembled PITSTOP2.EXE, it doesn't appear to be a hack, but quite deliberately adjusts itself for PCjr. The output still looks like a hack to me though...

VileRancour wrote:

The colors in PSTOP2.EXE make too much sense, and don't simply correspond to the nybble patterns used in CGA mode 6

That would be pretty simple --- the game would have lookup table which byte- or word-pattern to use for which original color; those pattern would simple be replaced.

reenigne wrote:

Most of the colours seem to be pretty close to prediction except that the saturation is lower on the real hardware.

Apparently the capture card indeed does use the color burst amplitude as a reference for the saturation. For some strange reason, everything looks spot-on except for artifact color D in 0A20 / 0A30, which is yellowish in all emulations, but pinkish in your capture. Odd.

Reply 523 of 757, by Servo

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can you check these too:
I, Damiano: The Wizard of Partestrada
Sherlock Holmes in "Another Bow"

no luck; I don't have an original of these, and strangely enough the cracked copies I tried work in DOSBox but do not work on real hardware including my PCjr!

Reply 524 of 757, by kao

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no luck; I don't have an original of these, and strangely enough the cracked copies I tried work in DOSBox but do not work on real hardware including my PCjr!

Sometimes cracked games were modified to work on newer computers. I found that out myself. For example, Retrograde Station had a DOS rip of Jumpman that someone inserted a slowdown feature in it (the original game runs too fast on 286+ machines). As a result, it was unplayable on a real XT due to running way too slow. Also the DOS rip of Big Top seemed to have this problem.

Galaxian is a real bugger. I don't know what exactly they did with all the DOS rips of it, but they kept throwing the monitor out of sync. Two different VGA monitors this happened and I could only get it to work on one old fixed-frequency display. Even then, the picture would sometimes roll and you had to bang F1-F2 repeatedly to stabilize it (the game uses those keys to move the picture left and right on CGA). And then on my real XT w/ CGA, I also got a blank picture.

Centipede had some issues as well. I tried the DOS rip from Retrograde Station and your shooter thing would move to the left side of the screen (on my XT) and shoot continuously, making the game uncontrollable. I suspect that it was one of those games that hooks INT 9h and somebody modified the keyboard routines so that they could reset the computer with CTRL+ALT+DEL.

I would like to find originals of the games on Ebay to test, but those are damn hard to run into.

Reply 525 of 757, by VileR

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kao wrote:

I would like to find originals of the games on Ebay to test, but those are damn hard to run into.

Quite a few of them have been dumped in original / uncracked form, but due to copy protection most of those would be in Teledisk format (or similar) which is no good for DOSBox.
By the way, the slowdown in Big Top was only applied to the lowest speed setting ("1") - the others were not affected. With some debugging it should probably be possible to deduce and restore the original delay values.

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Reply 526 of 757, by kao

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Quite a few of them have been dumped in original / uncracked form, but due to copy protection most of those would be in Teledisk format (or similar) which is no good for DOSBox.

AFAIK, all the images on Retrograde Station were ripped by Demonlord and I don't think he modified them beyond making alterations to the disk access routines so they could work with Flopper. I know the image of Jumpman on there didn't have the speed adjustment I mentioned. The DOS rips on the other hand seemed to have been old ones floating around the net for years that he just uploaded.

By the way, the slowdown in Big Top was only applied to the lowest speed setting ("1") - the others were not affected. With some debugging it should probably be possible to deduce and restore the original delay values.

I remember an old thread on here mentioning the address in Big Top where it had the timer value located (so that you could adjust the game speed), but I can't find it now and for all I know the DOS rip of Jumpman was even been done by the same person. Galaxian needs to be looked into as well. There's something those DOS rips are doing that's causing monitors to throw up and I don't know what it is. As for Centipede, the keyboard worked on my XT about 1 in every 10 tries.

Assuming the Retrograde Station images were otherwise unmodified, it may be possible to extract the games from them and make new, "clean" executables. This should be pretty easy since they're all <64k. I actually did it once with Pac-Man before Demonlord got around to making a DOS rip of that.

Reply 527 of 757, by VileR

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At least some of the DOS conversions were by Demonlord as well, signed and all; sometimes with additions, like providing an exit back to DOS. As for the disk images, the one for Big Top had the speed modification (the post you mentioned is here) - so it probably shouldn't be assumed that none of the others were modified. Flopper still had the games running natively on much newer hardware, and in some cases that might require more adjustments than just speed / disk routines.

Unmodified Teledisk dumps of the original floppies - those that exist, anyway - are just a safer bet for testing, especially on an actual XT.

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Reply 528 of 757, by Great Hierophant

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Try fixing the dump of or rip of Boulderdash, because it fails to work with either a PCjr. or Tandy 1000, DOSBox or real machines, and the more colorful graphics and enhanced sound effects are lost.

http://nerdlypleasures.blogspot.com/ - Nerdly Pleasures - My Retro Gaming, Computing & Tech Blog

Reply 529 of 757, by kao

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Unmodified Teledisk dumps of the original floppies - those that exist, anyway - are just a safer bet for testing, especially on an actual XT.

True, although it should be possible to disassemble those DOS rips and find out what's going on there. If Galaxian was modified for VGA compatibility, they sure screwed up because (as I said) it only worked on one of four monitors I tried it with. Centipede as well, and since that game is tiny (only like 13k), it should be easy to look at.

At least some of the DOS conversions were by Demonlord as well

He may well have done that DOS conversion of Centipede because I'd never seen it anywhere else online (only an unofficial Centipede clone made by some guy named R.J. Graafe). A bunch of other games though like Alley Cat and Dig Dug have been around the net for years and were probably cracked back in the 80s.

Reply 530 of 757, by kao

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Try fixing the dump of or rip of Boulderdash, because it fails to work with either a PCjr. or Tandy 1000, DOSBox or real machines, and the more colorful graphics and enhanced sound effects are lost.

By "real machine" do you mean XTs? Because I've played that on my 386 and Pentium many, many times with no problem.[/quote]

Reply 531 of 757, by ripsaw8080

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I've figured out a way to cleanly fix the speed problem with Big Top. The sector that is used to save high scores and settings also contains the delay values for levels 1-3 (don't ask me why), and some of the data in the sector is skewed by one byte. The correct delay values are there, but the skew causes level 1 to have a very long delay while levels 2-3 have next to none (like level 9).

Run the attached program in DOSBox where the BIGTOP.IMG disk image file is located; it copies the default data to the saved data within the image. Beyond fixing the speed problem, maybe it's also useful to be able to easily reset the high scores when you like.

Attachments

  • Filename
    btreset.zip
    File size
    280 Bytes
    Downloads
    57 downloads
    File license
    Fair use/fair dealing exception

Reply 532 of 757, by kao

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I've figured out a way to cleanly fix the speed problem with Big Top. The sector that is used to save high scores and settings also contains the delay values for levels 1-3 (don't ask me why)

Most booter games were not paragons of clean, orderly, well-structured programming. Someone made a complete disassembly of Jumpman and it's a horrible spaghetti code mess.

and some of the data in the sector is skewed by one byte. The correct delay values are there, but the skew causes level 1 to have a very long delay while levels 2-3 have next to none (like level 9).

So it's not an intentional adjustment, but a glitch possibly caused by extracting the game from the original floppy. That's very nice. I'm sure though that Jumpman was modified because that has no speed throttling for 286+ machines.

And I suddenly remembered now that Demonlord put an exit feature into Centipede (Alt+X). I'm going to guess that that somehow screwed up the keyboard routines in there (the code may be very timing-sensitive and this alteration could throw it off).

Reply 533 of 757, by Great Hierophant

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kao wrote:

Try fixing the dump of or rip of Boulderdash, because it fails to work with either a PCjr. or Tandy 1000, DOSBox or real machines, and the more colorful graphics and enhanced sound effects are lost.

By "real machine" do you mean XTs? Because I've played that on my 386 and Pentium many, many times with no problem.

[/quote]

No, I mean a real Tandy 1000 or PCjr. or the equilavent DOSBox modes, the image and rip does work in regular PCs and XTs and DOSBox's CGA machine type, but you only get CGA and PC Speaker sound.

http://nerdlypleasures.blogspot.com/ - Nerdly Pleasures - My Retro Gaming, Computing & Tech Blog

Reply 534 of 757, by kao

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No, I mean a real Tandy 1000 or PCjr. or the equivalent DOSBox modes, the image and rip does work in regular PCs and XTs and DOSBox's CGA machine type, but you only get CGA and PC Speaker sound.

Boulder Dash Series & PCJR

In this thread, Servo mentions that his original disk of Super Boulder Dash (a combo release of BD I and II) works fine, but the cracked version does not detect the PCjr for some reason.

From all evidence I can find, it seems like Boulder Dash was never released for the PC as a solo game, but only as this combo SBD disk, which seems to have had two entirely separate executables on it (one for the PC and one for the PCjr/Tandy). Thus, it may just be that all DOS rips on the net are the CGA-only one. This old Usenet post seems to confirm it.

https://groups.google.com/group/comp.sys.ibm. … f9979cf20fca814

Mobygames also has pictures of a later European release of BD

http://www.mobygames.com/game/pc-booter/bould … eCoverId,51638/

Unlike the original, this version appears to be DOS and not a booter and it does indeed have separate PC/PCjr executables.

Reply 535 of 757, by VileR

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I was able to locate individual DOS rips of BD I and II (each one being a different exe); so separate PC releases did exist. Unless there was somehow yet another version of SBD which separated the executables by game rather than machine type.... ugh.
Strangely enough, both of them have exactly the same issue in DOSBox - graphics are CGA only, but I do hear 3-voice music when machine=tandy or pcjr. That goes for SBD as well.

Wouldn't be the only instance of First Star being just plain weird with their releases - e.g. the two completely different versions of Rockford (one is CGA/EGA/Tandy, while the other one adds VGA support but changes the colors in the other modes) - so I wouldn't even try to guess what's going on here. Servo? Reading this? :)

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Reply 536 of 757, by kao

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I was able to locate individual DOS rips of BD I and II (each one being a different exe); so separate PC releases did exist. Unless there was somehow yet another version of SBD which separated the executables by game rather than machine type.... ugh.

Ok so BD and BD II were released in Europe as DOS disks with separate CGA/PCjr executables

http://www.mobygames.com/game/pc-booter/bould … eCoverId,46777/
http://www.mobygames.com/game/pc-booter/bould … eCoverId,70528/

However, as far as I can tell, the only US release was SBD, a booter with both games.

http://www.mobygames.com/game/pc-booter/super … eCoverId,28868/

Strangely enough, both of them have exactly the same issue in DOSBox - graphics are CGA only, but I do hear 3-voice music when machine=tandy or pcjr. That goes for SBD as well.

The DOS conversions on the net could have either been ripped from the SBD disk or they were the executables from the European releases.

I downloaded one from an abandonware site to test with and it exhibited some awfully strange behavior in DOSBox. The 3-voice PCjr music played if you let it go into demo mode (graphics were still CGA), but the in-game SFX were just the normal PC speaker except for the walking noise that Rockford makes. In addition, in PCjr mode, the game produced a continuous humming sound in the background. Also for some reason, it would randomly switch the background color to white or blue. The last one happened regardless of whether DOSBox was set to PCjr, Tandy, or CGA.

- so I wouldn't even try to guess what's going on here. Servo? Reading this?

He might also like to tell us how he made this emulator screenshot of BD running in PCjr mode. Apparently he knows something we don't.

http://www.mobygames.com/game/pc-booter/bould … eShotId,383720/

Reply 537 of 757, by Great Hierophant

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As I can see, the standalone releases seem to support the PC and PCjr. only, while SBD added Tandy support.

Maybe Servo has something the rest of us do not...

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Reply 538 of 757, by Servo

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Hello, I had been on vacation for a bit so I'm just now catching up on this thread; the Mobygames shots were done in DOSBox set to PCjr. Somewhere online I found a disk image of just Boulder Dash 1; it's been quite a while so I have no idea where. Booting it in DOSBox the PCjr graphics and sounds seem to work fine, however there is still a problem as only the first level works (I'm guessing a problem with the image).

Reply 539 of 757, by kao

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Somewhere online I found a disk image of just Boulder Dash 1; it's been quite a while so I have no idea where.

Maybe Retrograde Station?

If you had a solo BD disk image, then it may have in fact existed as a booter and not merely the combo SBD. I'd find it weird anyway if BD had been released standalone for the Apple, Atari, and C64, but not the PC.