SCPH-9002 Microstutter in 240p test suite "scroll test"

[bytestorm]

I have a SCPH-9002 (PAL) that I installed a DFO in. (and a modchip)

When I run the scroll test I get some microstutter every 1-2 seconds when scrolling the gray tiles vertically in some of the speeds, and even some "shimmering" in the trees in the background of the horizontally scrolling sonic stage...

I tried the test suite with my mega drive and its really smooth scrolling for both tests, but my PSX isnt quite there..

Both scroll tests can be run at different speeds, and it doesnt show in the slower speeds but when I up the speed a tick or two then Its quite visible..

Anyone had any similar issues with their PSX?

Thanks in advance!

[bytestorm]

Hmm tried to get some measurements while the test CD is running but its not the easiest to do since its quite cramped when the cd unit is mounted but here are some shots with the scope.. it looks a bit off indeed... since it should show 53.693175 MHz on NTSC and 53.203425 MHz on PAL.

NTSC = 53.6900

ntsc.PNG

PAL = 53.2003

pal.PNG

hmm.. not sure is my scope cant show the exact freq or if its actually wrong.. need to test something else somehow to determine the precision

[bytestorm]

I measured on the original clk source for the PAL signal and its 53.2040 (rounded up somehow from 53.203425 I guess?)

[MasterLink]

Just to rule out the TV, as I had a similar situation when using one of those cheap Hyperkin HDMI cables, is this a CRT or LCD? The shimmering in the trees happens from deinterlacing a non-interlaced source, and that too could be causing that stutter if the deinterlacer on the TV is wildly confused (namely that you also stated you don't see it on the slower speed). If the oscillator was the culprit, it would happen no matter what the speed, and shouldn't cause "shimmer".

[bytestorm]

Thanks for the input . I have tried on 2 different CRTs, one Sony Trinitron, one B&O. Even used 2 different brands of RGB cables (HQ), and no scart switch in between, just in case, but I still get the issues.. The horizontal shimmering is not much, but clearly visible.. But the vertical scrolling stutter is very prominent. I will recap the psu unit just in case...

But back to the speed question, how sensitive is the PSX in regards to the clk? the "real" NTSC clk is 53.693175, and mine 53.690000.. would that even be able to cause something like this theoretically? Or wouldnt it just be running smooth but at a slightly lower speed?

[MasterLink]

That extremely small amount shouldn't cause any issues. In fact, in general the clock would actually speed up or slow down the vertical retrace, therefore frame duplication shouldn't happen. So the fact frames are being duplicated (the micro stutter) is a tad unusual, but I have not done any oscillator mods to my system either (I don't have a single TV that'll accept 50Hz, so I can't even test this sadly). The shimmering though, can you possibly get a picture of it? I'm highly curious about that visually to ensure what I'm picturing in my head is what you're seeing.

Before a PSU recap though, I'd go ahead and check voltages and ripple since you have a scope. If there's no ripple and the voltages are right, the PSU does not need a recap then. (Not all old caps go bad).

[bytestorm]

Yeah I guess you are right.. the speed shouldnt cause this.. hmm
I tried to make a video of the shimmering but its very difficult to film the CRT screen to capture the shimmering effect with my phone.. so much else going on with the CRT that the phone captures. But I will try and see again after work!

What would be "acceptable" ripple on the outputs?

What else could cause something like this? I do have a modchip also in this unit. The PsNee on a ATTINY85.. but since I can see that the PSX actually reads the whole program into RAM and stops the CD unit after starting the test suite, then it wouldnt be the modchip either...

Ill start with trying to capture the video issues with my phone, and see what we get

[MasterLink]

Capturing a CRT shouldn't be too challenging if you know how CRT's and cameras work, it's more of a "can your camera let you manually set shutter speeds" thing..

Your shutter speeds you'll want to stick to are 1/30th and 1/60th for NTSC, or 1/25th and 1/50th for PAL. If your phone or real camera can't allow you to set a shutter speed, stick to a photo and just snap a photo with the glitched shimmering. I don't need a video anyway, just a photo.

[bytestorm]

When I got home I remembered that the test suite came in 2 versions.. one for real HW and one for EMULATORS.
First I thought it might be a silly test, but best to rule out all other posibilities.

I got the 240p emulator version upp and running in Duckstation, and I´ll be damned.. it behaves just as my schp-9002! The shimmering cant be seen in the emulator, but the vertical scrolling area gets the same exact stutters in the scrolling!

I am guessing that I am chasing a ghost here...??

[bytestorm]

I need to find a real game that has some infinite scrolling or something so that I can see if this really is a issue at all when playing real games hahaha damn I got totally stuck in my way of thinking after the DFO mod.. I really wanted to test that it was correct and thought the 240p test suite would probably be my best choice

[bytestorm]

I can also add, that I tried the 240p test suite in my genesis again, supersmooth scrolling.
Fired up the genesis emulator core in retroarch, loaded the test suite.. smooth scrolling in vertical test.
Loaded it again in psx emu Duckstation and it stutters in the vertical test.

[MasterLink]

For DuckStation, do remember your monitors refresh rate should ideally match the emulated system. 50 or 100Hz for PAL, 60 or 120Hz for NTSC. If you already did that and DuckStation still stuttered, yea sounds like the 240p test suite is messed up. On my NTSC machine though I don't have this issue on any of my PS1's (from DTL-H1001H to SCPH-5501).

At least it's not the Dreamcast version of the 240p test suite, that version is what I'd call, "hot garbage". It's not a good port, it stutters all the time, made worse if you had a VGA cable attached. lol

[bytestorm]

Yeah my screen is set to 60hz refresh rate.

Genesis NTSC 60hz (emulator), the test suite is silky smooth in both hori and vert tests
Duckstation 60hz emulator, vertical test stutters at the higher speeds, just like my psx

in this test

Skärmklipp.PNG

Really strange that your psx doesnt... do you have it connected to a scart (rgb) CRT also?

[MasterLink]

I'm connected to my TV via S-Video, both on an LCD and CRT.

Upon very closer inspection, there *is* a stutter I didn't notice before. It's so random for me though, it's not once per second, more like once every 10ish seconds. And sometimes in-between almost random. I should mention my system is a DTL-H1001H and has a Rev A GPU, you have the later revision GPU with SGRAM (mines dual ported VRAM). Which I guess could explain the difference, but no, after looking even closer, there is indeed stutter here as well, it just seems to manifest a little differently.

1000015620-01.jpg

[bytestorm]

Thank you so much for testing! I must admit, the stutter isn´t really every 1-2 seconds, but more like every 4-5th maybe if I let it go at the same speed. Initially I jumped alot up and down with the speed and thats maybe why I experienced it more frequently (I was also quite frustrated since I followed the guides extremely carefully ... so yeah, its more like around 4-5 seconds inbetween if I just let it run at the same speed all the time (quite fast)

Wow its a relief that you could see it also! Phew.. Thanks again!

Ill see if I can make a report on the github

[bytestorm]

Ill make sure to test it in PAL mode first also to see if the stutter occurs in both or just one.

Nice gaming setup by the way!

[MasterLink]

Yea I noticed that even pressing buttons to change speed almost always results in an immediate stutter on the first few frames after the speed change, so there's very much a bug at least as far as I'm concerned.

And lol thanks, that's only a portion of what's visible. There's actually a whole generation of consoles hidden in there. Not seen is a Saturn with a 5" color CRT next to it (currently plugged into the PSX's direct AV out right now, as I was testing the test suite for you on both a CRT and LCD), an OG Xbox to the left of the TV, Genesis/CD/32X and an Atari VCS. All of them are actually plugged into the main TV, that's what the unit under the TV is for, it selects which console gains access to the TV's AV or S-Video jacks. Dreamcast is the only one plugged straight into the TV via VGA.