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Exidy Sorcerer II Questions

There's definitely something wrong with the Sorcerer still. When playing a game like Astro Attacker the screen flickers and glitches in places. I'm guessing it needs some more caps replaced.

On the plus side, it *is* working.
 
After tempest and I fixed his we powered mine up only to find a blank screen. Today I reseated all the chips (they are all socketed because I replaced all the chips back in the day when I the board was blown and given to me). Joy of joys, it powered right up today and reported THE TOP OF RAM IS DFFF ! Now it's running a test on all 56K RAM.

Mine also shows a few briefly blanked pixels when it writes to the screen. I think it's normal for the video circuit to blank during CPU accesses to screen RAM. To see an extreme case run the Monitor command TE F600 F700. As it tests screen RAM you see many dropouts (you can also see the test patterns used). When that's done run TE FE00 FF00 and watch the user characters show the bit patterns. Now run TE 0000 00FF and see only a few brief blanks as it tests non-screen RAM.

tempest, is that the "ripple" you see? Or do you see a waviness in the position of thr characters? We looked at your power rails on my scope and they looked very flat, so I think your power caps are fine. I suppose bad decoupling caps (the small ones all around the board) could cause glitches in the display circuit. Can you post a video of the problem?
 
I did the tests above first on a rock-steady LCD monitor. Then I repeated them on an old green screen CRT. It shows the same brief blanking during screen access but it also shows some side-to-side jitter as well. That's like what I remember seeing on your 1702.

My conclusion is that both our machines show the same video artifacts which may be normal. Would other Sorcerer owners please repeat the tests and report?

BTW there is a bit in the Sorcerer's input port so the CPU can read when vertical blank is happening so as to avoid that blanking. The better games use that to give a solid display IIRC.
 
Also run the Monitor command DU 0 FFF. As the screen scrolls you see a lot of blanking and jitter because the Monitor's scroll routine does not wait for vertical blank. It just does a LDIR.

Do some other programs have better scroll routines?
 
I'll have to try this tomorrow. IIRC there were parts of the graphics that blinked or sort of dropped out. Like flicker in a NES game. I'll get a video of it tomorrow.
 
Oops I goofed above. The input bit reads horizontal blank, not vertical.
 
ClausB said:
I did the tests above first on a rock-steady LCD monitor. Then I repeated them on an old green screen CRT. It shows the same brief blanking during screen access but it also shows some side-to-side jitter as well. That's like what I remember seeing on your 1702.

My conclusion is that both our machines show the same video artifacts which may be normal. Would other Sorcerer owners please repeat the tests and report?

BTW there is a bit in the Sorcerer's input port so the CPU can read when vertical blank is happening so as to avoid that blanking. The better games use that to give a solid display IIRC.
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One of the "advantages" of LCD monitors is that they sample the video signal and get for free a temporal aliasing; doing this, all waving phenomena always disappears :)

As yours, mine returned no video signal after some time unplugged. As it doesn't gives signal (I mean even no black screen) I'm suspicious about the connector itself, it has always been extremely flaky. I'll check this and if I'm able to fix it I'll report back the info.
 
Ok here are three videos I made of my Sorcerer. The first one shows what happens when I load a game. The second shows what happens during a game. The third one shows the same game on another monitor (crappy composite, but it does the same thing). Ignore how the top and bottom of the screen are cut off, the Sorcerer doesn't seem to want to center right on my Sony PVM monitor (some systems are off center on it for some reason).

As you can see I'm getting scanlines that are dropping out and some massive line interference when there are a lot of graphics on the screen. This can't be normal for the Sorcerer.

I apologize in advance for how big these files are, you may need to download them first.

Video 1: http://www.atariprotos.com/temp/sorcerer1.mov
Video 2: http://www.atariprotos.com/temp/sorcerer2.mov
Video 3: http://www.atariprotos.com/temp/sorcerer3.mov
 
It would be better to compare with exactly what mine can run, which is only Monitor commands. Can you video the four commands I posted above?
 
Those Monitor commands look exactly the same as they do on mine with a CRT. If it's not normal, then we both have the same problem. Would other Sorcerer owners please run the same commands and report back?
 
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Dumb question. Could this issue be caused by trying to run PAL software on an NTSC Sorcerer? I somehow doubt it, but I have no idea if these games I'm trying to run are from the US.
 
tempest said:
Dumb question. Could this issue be caused by trying to run PAL software on an NTSC Sorcerer? I somehow doubt it, but I have no idea if these games I'm trying to run are from the US.
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No. From my understanding that is only an issue if you are dealing with colour video.

I just took a look at your video. Hmm...Unfortunately my Sorcerer is packed away, my computer-shack workdesk is cluttered with another project and my evenings are taken up with other things at the moment otherwise I'd run the game and compare. However, to me that flickering doesn't look that unusual for the type of computer it is. I'm assuming the Sorcerer uses the same kind of video RAM setup that the TRS-80 Model 1 uses. They are both similar technology typical of around the late 1970s. Certainly such flicker is completely normal (in fact I've seen worse) with some arcade games on the TRS-80 Model 1 (a machine I've a lot more familiar with). Here's a section of from a wikipedia article on the TRS-80 Model 1.

"Any access to the screen memory caused "flicker" on the screen. The bus arbitration logic would block video display while access was given to the CPU, causing a short black line. This had little effect on normal BASIC programs, but fast programs made in assembly language could be affected. Many software authors were able to minimize this effect. Notwithstanding this primitive display hardware, many arcade-style games were available for the Tandy TRS-80."

I think your Sorcerer is behaving in a normal manner.

Tez
 
You think so? Im pretty familiar with TRS-80 games and their flicker, but his seems kind of severe to me. I can understand the little black lines during busy cpu usage but the massive picture distortion can't be normal.
 
tempest said:
You think so? I'm pretty familiar with TRS-80 games and their flicker, but his seems kind of severe to me.
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Well, as it says in the article...it can depend on how well the software writer was able to minimize this effect. Some TRS-80 Model 1 games on a real unmodified TRS-80 model 1 flicker quite badly....others hardly at all. A TRS-80 Model III/4 has far less flicker with the same games, due to improved circuitry.

It still looks normal to me, and one other poster gets the same symptom. So your machine may be ok. If I get some time in the next few weeks, I'll try to drag my own Sorcerer out to compare.

Tez
 
I was just looking at your video on YouTube Tezza, and I don't see the same interference when you play Astro Attacker as I have. It's hard to see, but I only see some flicker. I don't see the glitches that I have.
 
tempest said:
I was just looking at your video on YouTube Tezza, and I don't see the same interference when you play Astro Attacker as I have. It's hard to see, but I only see some flicker. I don't see the glitches that I have.
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Ok. There is some obvious flicker when I'm showing that game on the video. It didn't look too dissimilar to me to what yours was doing? If yours is a lot worse than that, well maybe something is a bit degraded or slightly out of tolerance.

Tez
 
I'll have to look tomorrow on a bigger screen (I'm on my iPhone at the moment so it's hard to see). From what I saw in your video there's just some flicker. On my system I'm seeing some actual graphical glitches. For example the graphics in the laser and fuel gauges actually 'glitch' like the interference on a badly tuned tv.
 
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I just looked at your video on a bigger screen. It does look like the same interference that I have on my Sorcerer, although I think mine is a little bit worse (but that is hard to tell for certain). I still wonder if failing caps might be making the problem worse.

Interestingly look at the Sorcerer in this video: https://www.youtube.com/watch?v=FedQ4QdcsnU

A rock solid picture with no glitches. It could be because it's just displaying a simple picture, but it still makes me wonder.
 
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