VOGONS


Ghostbusters

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First post, by trebor

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Bottom of screen which shows score/status has 'flashing' corruption throughout the game while playing. Machine type is set to pcjr for best graphics and sound possible.

A screenshot is attached but obviously cannot demonstrate the 'flashing'/corruption properly.

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Reply 2 of 22, by trebor

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Sorry, I do not have a pcjr handy for me to check now; however, I do not recall it having vertical line corruption and choppy flashing like colors.

Granted there may have been some flashing of solid red against the bottom during the street scenes, but the emulation of this feature is off and is corrupt on many of the other gameplay screens.

Reply 8 of 22, by h-a-l-9000

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Ok, on the box...

However I wouldn't trust the Mobygames technical details there because they throw all games in the Tandy/PCJr category, regardless of wether they only work on one of these two systems.

1+1=10

Reply 9 of 22, by Servo

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How does it look on real hardware?

Looks fine (no flashing/corruption/color problems, etc); if I recall the game relies on 4.77Mhz 8088 timing (similar to California Games palette changing trick) to switch video modes between 160x200 (playfield) and 320x200 (scores) or something bizarre like that. On real hardware this isn't noticeable and looks pretty good. It will display correctly on a Tandy 1000 with an 8088; it does not display correctly on a Tandy with an 8086 (or higher). Unfortunately I can't grab any captures from real hardware to demonstrate at the moment as I sold my 8088 Tandy and my PCjr joystick is broken.

Reply 11 of 22, by trebor

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I presume the Tandy emulation under DOSBox is the 8086 variety. Setting Tandy as the machine type results in many horrid graphic corruptions starting with loading the car to all game play screens.

Is there any way of setting or (If not emulated yet) plans of emulating a Tandy 8088 variety? Or is fixing the PCJR display issue(s) more likely?

Reply 12 of 22, by h-a-l-9000

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> I presume the Tandy emulation under DOSBox is the 8086 variety.

Not at all. I've implemented the on-screen mode switch 16 lowres <-> 4 medium res only for PCJr, thus the mess with machine=tandy. The DOSBox Tandy CPU is still a 486 as all machine types.

> fixing the PCJR display issue(s) more likely?

It probably requires a clock-cycle exact instruction emulation.

With normal core and 260 cycles, timed=true it it doesn't seem to flicker all that much?

1+1=10

Reply 15 of 22, by trebor

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Not a problem. See the attached. The screenshot(s) are really not doing the problem and the improvement justice as it doesn't capture the flashing as well as all the gameplay screens.

The problem was much worse than the first screen capture highlighted and has improved much more than this attached screenshot displays.

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    GBTandy.PNG
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Reply 16 of 22, by Servo

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To clarify what I wrote earlier, I'm pretty sure the reason the game doesn't display correctly on an 8086 is entirely a speed issue; the game was (more or less) playable on an 8086, but it had a flickering/corrupted display similar to what is seen in DOSBox. It doesn't work right on a fast (7.16Mhz) 8088 either.

On my Mac I was able to reduce the flicker quite a bit by setting the cycles to 254, but it's still not perfect. After double checking, the Tandy 1000 HX has a 7.16 Mhz 8088 (thought it was an 8086 for some reason!), and luckily it's possible to slow the speed to 4.77Mhz. Running the game at full speed on the HX doesn't work right, but slowed to 4.77Mhz seems ok and I took a few photos. There's still some oddities (color and odd pixels) in DOSBox compared to this (which, if my memory is correct, looks pretty much the same as a PCjr)

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Reply 18 of 22, by h-a-l-9000

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I'd need a photo of the title (music) and equipment screen too. Reason is the bottom bar on this picture displays as white and light blue, whereas the game programs light grey and normal blue. This could be a Tandy specific thing. Also, when switching between equipment screens (1-3), does the screen go black or stay brown?

1+1=10

Reply 19 of 22, by Servo

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h-a-l-9000 wrote:

I'd need a photo of the title (music) and equipment screen too. Reason is the bottom bar on this picture displays as white and light blue, whereas the game programs light grey and normal blue. This could be a Tandy specific thing. Also, when switching between equipment screens (1-3), does the screen go black or stay brown?

I think the color difference may be more a problem of old monitor and not perfectly exposed photo. I'm traveling at the moment, but I'll double check take some more photos when I get home.