 No.10783
Tafoid Administrator
Jun 9, 2014, 23:58
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I can acknowledge the slowdown in the 2 places mentioned and that overclocking appears to fix it, but it might not be the correct fix. Anyone with an original CVS CPU with this cartridge or possibly another game in the library could be used to scope for clock speeds. |
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 No.10784
hap Developer
Jun 10, 2014, 16:48
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i doubt that the emulated clockspeed is wrong, I'd look elsewhere for causes of this slowdown |
 No.15321
Machone Tester
Aug 10, 2018, 08:30
edited on: Aug 10, 2018, 08:31
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Overclocking the CPU, as mentioned, fixes the problem with the swinging ropes scene. However, there is another issue in that parts of the emulated game are actually running too quickly regardless of whether the CPU is overclocked or not. Compare the title screen animation with the hunchback and the girl and you'll see that MAME is far too fast. So there appear to be two different issues: the first is that there is a CPU problem causing slowdown on the fire pit stage, and the second is that the emulated game is running ahead of the pcb. As these Century games were produced in the UK I think it's a fair assumption that they were developed using a PAL 50Hz system. With this in mind (and with the game CPU overclocked - 150% or 200%, it didn't seem to matter), I tried to sync the title screen to MAME and found that they synced up almost perfectly at 51Hz. Also, the hunchback jumping from right to left in the opening scene is also indistinguishable from the video at this speed. Obviously proper measurements need to be taken from the pcb to know for sure, but I just thought I'd share my observations. |
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No.15331
kazblox Tester
Aug 12, 2018, 01:30
edited on: Aug 12, 2018, 01:36
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Century driver is kludge. Given it's derivative nature hardware wise, the raw screen params should presumably be similar to that used in the Lazarian driver, which give a 50.541416Hz refresh rate. Galaxia hardware emulation in MAME also suffers from the same problem. All except the Lazarian driver need a big rewrite to properly function. |
 No.15335
cuavas Administrator
Aug 13, 2018, 15:59
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Lazarian is pretty whacky hardware - it's abusing a Signetics PAL sync generator to generate a non-standard resolution. It (ab)uses some flipflps to do a symmetric divide-by-three on the pixel clock so it can run layers at different resolutions, and visible lines aren't a whole multiple of three clocks long. I wouldn't believe anything has similar timings unless someone produces a schematic or traces a board and shows that it's hooked up the same way. |
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No.15358
kazblox Tester
Aug 29, 2018, 02:52
edited on: Aug 29, 2018, 03:03
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Lazarian is indeed, a complex and intricate system. There is schematics for Galaxia available. I have attempted to read them a while back, and while my memory may be fuzzy, the pixel clock circuitry is similar; a PAL S2326 sync generator is also abused to scale a separate layer in Galaxia for the discrete color stars. I am not in a position to reread the entire Galaxia schematics again to make sure what I'm saying is right though, so everything I am saying could be wrong. However, Galaxia != CVS hardware in any complete stance other than that their hardware nature is derivative and shares major components. For all I know, the pixel clock circuitry is simplified, or different from that from Galaxia or any other games on previous Zaccaria hardware. I only know about the former, and bare dirt about the latter. So, please excuse my misunderstanding if the comments are irrelevant. |