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Dave
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oops - was posting on wrong board!
Post Posted: Sun Jul 22, 2001 5:25 pm
Yep - my timing is probably way off hence funny speech.

are you certain the z80 speed is 3.57954 mhz by the way?
I've seen 4mhz quoted in some docs and wasn't sure...

So the PAL version has 304? lines and the NTSC has 262, thanks.
At the moment I'm not really differentiating between the two.

By the way, a quick plea for help: does anyone know of any software to help delete mail from POP3 servers without downloading it? I'm getting a repeated virus attack (Word scripts, .com Executables etc) every hour or so and keep on having to telnet to port 110 to delete it.
 
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Email header reader
Post Posted: Sun Jul 22, 2001 6:14 pm
Quote
> By the way, a quick plea for help: does anyone know of any software to help delete mail from POP3 servers without downloading it? I'm getting a repeated virus attack (Word scripts, .com Executables etc) every hour or so and keep on having to telnet to port 110 to delete it.

You want a header reader. I use this one here, for no good reason other than it works fine and it was the first one I tried. Your mail client might have one included, I know FoxMail does. They're well worth using, if only so you can delete the spam without downloading it.

Maxim
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break on through to the other side
Post Posted: Sun Jul 22, 2001 7:08 pm
Welcome to S8-Dev, Dave.

This is my favorite forum ever.


Quote
> Yep - my timing is probably way off hence funny speech.

> are you certain the z80 speed is 3.57954 mhz by the way?
> I've seen 4mhz quoted in some docs and wasn't sure...

A lot of earlier docs have a number of guestimates, and I don't think any of the docs out there have the correct clock speed. Hence Richard Talbot Walkin's doc (still the best all-around SMS programming documentation) still lists the formula for converting the 10bit PSG frequency to a real frequncy as : 125000/(value).

The PSG seems to run at 1/16th the main CPU clock (derived from the same crystal), and each full cycle is at least two clocks (one high, one low), so cpu clock/32 seems to be the right way to get the frequency constant.

4000000 / 32 = 125000, hence the estimate, but when I put that into practice my frequencies were definately too high.

3579540 / 32 = 111860.625, which is what I use, and when Ilisten to it side by side with my Game Gear (no working SMS right now) it sounds perfect to me.

Charles Mac Donald's VDP doc is very accurate, BTW.

There's a project going here at s8-dev to better document the SMS/GG family with new information that's been uncovered since the few documents out there were released. As of yet we have a structure but I don't think anyone's submitted a document. I was one of the chief complainers who wanted to get this project started, and yet I haven't done a thing for it. This is probably because I suck.

Quote
> So the PAL version has 304? lines and the NTSC has 262, thanks.
> At the moment I'm not really differentiating between the two.

I think the extra lines are only used a few games that enable the extra rows bit in the VDP, which would be those codemasters games. Otherwise, PAL users see the same display as NTSC users, but with 50 frames per second (how does that look ona PAL TV btw? Does the screen get stretched vertically, or are there black borders filling the empty area?)


To answer your question on the other forum, pulse width modulation (PWM) is the technique for audio playback used in Alex Kidd and the Lost Stars, Space Harrier, After Burner, Alien Syndrome, Great Basketball, and a number of others. Rather than writing 4 bit samples to the volume registers of each tone channel at regular intervals, PWM samples are played with all the channels toggling between all-on and all-off.

Thus, your output wave is either high or low at any point.

The technique for building a PWM sample involves timing the intervals between high and low in such a way to simulate a greater bit depth, the exact details aren't clear to me because I haven't looked into adding PWM to my projects. It's the same technique used to get sample playback out of those piezo speakers (the little speakers that get either be set hi or low with nothing in between), used in wristwatches and cheap LCD games. Normally they're just used for sounding beeps at various pitches, but you can use them to play samples... the standard PC speaker that's been in every PC since the dawn of PC compatibles is also a speaker like this, I remember games from the 286-386 era which used PWM techniques to play samples or synthesized music. I even remember a mod player that played back through the PC speaker.

PWM samples are much scratchier than PCM, you can recognize them right away. But they're also louder (notice how faint the samples are in Lemmings and Arcade Smash Hits), and I'm fairly certain they use up a lot less cartridge space.
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Z80 Frequency
Post Posted: Sun Jul 22, 2001 7:11 pm
Quote
> are you certain the z80 speed is 3.57954 mhz by the way?
> I've seen 4mhz quoted in some docs and wasn't sure...


Well, the Z80 used in the SMS is a 4MHz part, but it isn't actually run at that speed. The actual speed is 3.57954MHz on a NTSC Master System and 3.54689MHz on a PAL one.

Mike

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Re: break on through to the other side
Post Posted: Sun Jul 22, 2001 7:20 pm
Quote
> 3579540 / 32 = 111860.625, which is what I use, and when Ilisten to it side by side with my Game Gear (no working SMS right now) it sounds perfect to me.

When I was doing the sound tests I used Cool Edit's FFT to tell me the fundamental frequency generated by the tone generator in realtime, which gave me very similar values for the constant. The granularity of the PSG's frequency setting means almost every note is slightly off but it's certainly beyond my hearing. I could do some more tests like that if anyone is bothered.

Quote
> I think the extra lines are only used a few games that enable the extra rows bit in the VDP, which would be those codemasters games. Otherwise, PAL users see the same display as NTSC users, but with 50 frames per second (how does that look ona PAL TV btw? Does the screen get stretched vertically, or are there black borders filling the empty area?)

It's squashed (maintaining two TV lines per SMS screen line), so we get big borders at the top and bottom of the screen and elliptical circles, rectangular squares, and so on. Would the Codemasters "overscan" games be off-screen on an NTSC system?

Quote
> I even remember a mod player that played back through the PC speaker.

Hey, yeah, I used to use that :) back before I bought my first sound card...

Quote
> PWM samples are much scratchier than PCM, you can recognize them right away. But they're also louder (notice how faint the samples are in Lemmings and Arcade Smash Hits), and I'm fairly certain they use up a lot less cartridge space.

The all-time quietest one has to be "Welcome to Populous". It's hardly louder than the background buzz from the SMS.

Maxim
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Post Posted: Sun Jul 22, 2001 7:22 pm

Quote
> are you certain the z80 speed is 3.57954 mhz by the way?
> I've seen 4mhz quoted in some docs and wasn't sure...

It's 3.579545 MHz for purists. ;) This works out to 227.7 cycles per line, if you are rendering everything on a line-based level.

Quote
> So the PAL version has 304? lines and the NTSC has 262, thanks.
> At the moment I'm not really differentiating between the two.

PAL screens have 312 lines, NTSC are 262. Apart from the CPU clock speed difference, I think the only other change in PAL machines, the V counter counts up a bit differently during V blank (as it has to span 312 lines instead of 262). If you really want to get technical about how the NTSC screen is made up, check out the screen timing section in the TMS9918 manual, which is exactly the same as the SMS VDP.

The manual does not, however, explain timing for PAL chips. :(


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WHAT ?!
Post Posted: Sun Jul 22, 2001 8:41 pm
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> PAL screens have 312 lines, NTSC are 262.

From Meka:

TV_Type_Table_Entry TV_Type_Table [] =
{
{ "NTSC", 262, 60 },
{ "PAL/SECAM", 302, 50 }
};

Guys, don't tell me I've been working with a typo since A YEAR.
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Re: WHAT ?!
Post Posted: Sun Jul 22, 2001 9:09 pm

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> Guys, don't tell me I've been working with a typo since A YEAR.

Well, now you know what the problem is. :)

Seriously though, PAL screens do have 312 lines, not 304.

I could make it harder by telling you that really, due to interlacing, NTSC frames are 262.5 lines and PAL frames are 312.5 lines (which is why you often see an interlaced frame referred to as having 525 lines (NTSC) or 625 lines (PAL). :)


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I always thought the ones on California Games were pretty damn quiet *nt*
Post Posted: Mon Jul 23, 2001 11:55 am
Quote
> > 3579540 / 32 = 111860.625, which is what I use, and when Ilisten to it side by side with my Game Gear (no working SMS right now) it sounds perfect to me.

> When I was doing the sound tests I used Cool Edit's FFT to tell me the fundamental frequency generated by the tone generator in realtime, which gave me very similar values for the constant. The granularity of the PSG's frequency setting means almost every note is slightly off but it's certainly beyond my hearing. I could do some more tests like that if anyone is bothered.

> > I think the extra lines are only used a few games that enable the extra rows bit in the VDP, which would be those codemasters games. Otherwise, PAL users see the same display as NTSC users, but with 50 frames per second (how does that look ona PAL TV btw? Does the screen get stretched vertically, or are there black borders filling the empty area?)

> It's squashed (maintaining two TV lines per SMS screen line), so we get big borders at the top and bottom of the screen and elliptical circles, rectangular squares, and so on. Would the Codemasters "overscan" games be off-screen on an NTSC system?

> > I even remember a mod player that played back through the PC speaker.

> Hey, yeah, I used to use that :) back before I bought my first sound card...

> > PWM samples are much scratchier than PCM, you can recognize them right away. But they're also louder (notice how faint the samples are in Lemmings and Arcade Smash Hits), and I'm fairly certain they use up a lot less cartridge space.

> The all-time quietest one has to be "Welcome to Populous". It's hardly louder than the background buzz from the SMS.

> Maxim
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Thanks!
Post Posted: Tue Jul 24, 2001 8:17 am
Switching to 312 switched the necessity of having to trick in MEKA.NAM for a few games (Micro Machines included), so you can run them without MEKA.NAM anymore (which is important).
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Lamer questions... (sorry)
Post Posted: Tue Jul 24, 2001 3:57 pm
First of all, Dave... welcome to S-8 (not G-8) Dev.
I'm one of the lurkers here.. I pop up whenever I see something ineresting (usually music stuff).
I have no programming experience at all, and I'm not about to go and get any either :)

Anyway, I'm sure you get these questions all the time, and I'm sure you hate them, but I have a valid reason for asking, as I shall explain:

You see, in March (or thereabouts) of 2000, I had to move out of 'home' and into a place that had no phone, and such I had no internet access untill February this year when I moved in with my sister.
Anyways, at the time of my leaving the internet, two of my favorite emulators were DTMNT and DGen. The former because it was the only Turtles emulator that would run on my P133, and the latter because it sounded so damned cool... on my sisters' computer.

Well like I said, I came back online in February this year, only to find that both of those emulators had disappeared off the surafce of the planet! I couldn't find them anywhere, and I really didn't want to resort to MAME to get the Turtles experience, mainly because MAME is (or was) a bloated heap of code that ran too slow for it's own good.

Where did they go? What happened? Where can I find them?

Anyway... that's what I have to say... aside from 'please visit my page of compositions... I got the highest score out of my whole year level because of the pieces' :-D

~unfnknblvbl

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Re: Lamer questions... (sorry)
Post Posted: Wed Jul 25, 2001 9:57 pm
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> Well like I said, I came back online in February this year, only to find that both of those emulators had disappeared off the surafce of the planet! I couldn't find them anywhere, and I really didn't want to resort to MAME to get the Turtles experience, mainly because MAME is (or was) a bloated heap of code that ran too slow for it's own good.

> Where did they go? What happened? Where can I find them?


Currently the best Genesis emulator is Gens. If MAME is too slow for your machine, I guess you might be able to find DTMNT from somewhere, but personally I don't use it anymore.
Good luck, but this is a bit off topic.
 
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Games on PAL TVs
Post Posted: Fri Jul 27, 2001 10:53 am
Quote
> I think the extra lines are only used a few games that enable the extra rows bit in the VDP, which would be those codemasters games. Otherwise, PAL users see the same display as NTSC users, but with 50 frames per second (how does that look ona PAL TV btw? Does the screen get stretched vertically, or are there black borders filling the empty area?)

Here's what a Codemasters game looks like:



Here's what a standard game looks like:



ie. squashed (it maintains 2 interlaced TV lines per line of pixels). Note that on most TVs, the tube cuts off quite a lot of the image, so the gaps look slightly smaller. I'd be interested to see a full-screen grab of an NTSC system for comparison.

Maxim
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