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Re: 8086 average clocks per instruction (when running normally)?

Posted on 2016-03-07, 21:08

So if I understand all this correctly it's simply a case of missing documentation? If there was a proper documentation with exact cycles for all instructions and hardware, a fully cycle accurate PC emulator should have long existed by now? But it doesn't, simply because there is no (proper) …

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Posted on 2016-03-06, 23:08

by superfury

in PC Emulation

So the actual reason that 8088 MPH is making slow music at some parts of the demo(like the 1K color image, where it shows on the vga only half a screen with the bottom part in text mode with blinking text (1K colors text enlarged) and the top half shaking with the data from the 1K image(1K colors on …

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Posted on 2016-03-06, 21:17

by superfury

in PC Emulation

Why from 0 to 65535? The previous signal would be (as given by the PC Speaker) -32768, the new sample +32767, so the output should move as a result from the high pass filter (previous was zero) to 32767, not 65536? Unless you would double the amplitude from the PC Speaker itself(which isn't done)? …

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Posted on 2016-03-06, 20:00

by superfury

in PC Emulation

I notice that increasing the high pass filter to 18.2Hz removes the echo effect that occurred with 1Hz. Audio sounds fine so far. Still untested on 8088MPH though as the pc I was working on (The 2GHz one) was too slow(CPU now running at 10% due to the PC speaker's heavy low pass filter(1.19M …

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Posted on 2016-03-06, 16:57

by superfury

in PC Emulation

Emmm. Jumping up and down by 64K still fits inside 16-bits? Also, the filter only attenuates(lowers volume), not amplifies it?

Re: x86EMU emulator releases

Posted on 2016-03-05, 16:13

by superfury

in Release Announcements

My latest build: x86EMU_20160305_1656.zip - MIDI: Implemented default instrument #0. - Improved MIDI volume according to Soundfont 2.4 specification. - Implemented MIDI concave/convex formulas. - Changed PC Speaker low pass to run at 1.19MHz instead of 44.1kHz, before downsampling, for accuracy. - …

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Posted on 2016-03-05, 15:44

by superfury

in PC Emulation

Also, strange enough, when I disable the high pass 1Hz filter now, I get clear sound when the PC speaker makes music (on the slow PC running at ~10% CPU Speed now on the 2GHz Pentium Dual core P6100 processor) in all recordings, but the output gives some low frequency rumble (about 20-50Hz) without …

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Posted on 2016-03-04, 15:09

by superfury

in PC Emulation

I've improved my PIT emulation a bit with more accuracy. Although it still doesn't sound fully right. http://www.filedropper.com/speakerlog201603041603 The current source code: https://bitbucket.org/superfury/x86emu/src/cc … pit.c?at=master

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Posted on 2016-03-04, 12:05

by superfury

in PC Emulation

I am wondering though: Besides the filters not working properly(apparently), is the PIT output itself even correct? time_ticktiming += timepassed; //Add the amount of time passed to the PIT timing! //Render 1.19MHz samples for the time that has passed! length = (uint_32)SAFEDIV(time_ticktiming, time …

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Posted on 2016-03-03, 23:44

by superfury

in PC Emulation

The low pass filter uses (as well as the low pass of the MIDI renderer and the high pass 1Hz used before sending the full mixed output of all emulated hardware to SDL) a simple RC filter: OPTINLINE static float calcSoundHighpassFilter(float cutoff_freq, float samplerate, float currentsample, float …

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Posted on 2016-03-03, 21:06

by superfury

in PC Emulation

I've made a new recording using the latest commit (which changes the low pass filter back to 20kHz, applies the filter on the 1.19MHz signal(which is increased to 16-bit depth using SHRT_MIN and SHRT_MAX) and logs both the raw samples (SPEAKER_LOGRAW to speakerraw.wav) and the filtered samples ( …

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Posted on 2016-03-03, 14:15

by superfury

in PC Emulation

This is the current processing, generating samples from the PIT until the current time is reached(timepassed is the time the CPU, PIT and all timed hardware has executed the current instruction). speaker_tick is the amount of ns for each 44.1kHz sample to be generated. Essentially 1000000000/SPEAKER …

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Posted on 2016-03-03, 12:26

by superfury

in PC Emulation

So I should only low pass the PIT 1/0(binary) stream with 16 2/3 kHz, then downsample to 44.1kHz(which is done by skipping those ~25 calculated samples for getting each 44.1kHz sample)? The low pass filter will actually do the hard work? Or is actual 20kHz averaging before down/upsampling still …

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Posted on 2016-03-03, 08:18

by superfury

in PC Emulation

It currently creates the 1.19MHz samples (just PIT rendering 1s and 0s based on it's input by the emulated CPU). Then it first low pass filters it with 16666 2/3kHz to filter out the higher signals. Finally it downsamples it to 44.1kHz by skipping samples (~26 PIT samples skipped for every 44.1kHz …

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Posted on 2016-03-03, 06:08

by superfury

in PC Emulation

My current understanding of PC Speaker sampled output is that you generate PWM to create samples. The PWM itself can indeed be done at any speed, but with the PC speaker it only makes sense when executing pulses within 60 us? Since it takes 60us to move fully from off to on state or backwards? Using …

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Posted on 2016-03-02, 22:18

by superfury

in PC Emulation

Any idea on the filter to use instead(same with the high pass filter of 1Hz used in the sound module for protection)? It is the only simple and clear filter I could find in C code. Only highly complicated formulas otherwise(never did any high level algebra after middle school to be able to fully …

Re: PC speaker gives incorrect results (when low and high pass filtered) and with 8088 MPH?

Posted on 2016-03-02, 18:51

by superfury

in PC Emulation

This is my current rendering loop converting the PIT samples into a 44.1kHz sample: //render_ticks contains the output samples to process! Calculate the duty cycle by low pass filter and use it to generate a sample! for (dutycyclei = render_ticks;dutycyclei;) { if (!readfifobuffer(PITchannels[2]. …

Re: PC speaker gives incorrect results (when low and high pass filtered) and with 8088 MPH?

Posted on 2016-03-02, 17:56

by superfury

in PC Emulation

Yes, just like I said earlier, although I don't know those factors on the top of my head. But essentially around 72 PIT samples make the cone move enough to be able to process the movement from 0 to 1 or in reverse. If this wouldn't be true, any PWM generating PCM samples using that method would …

Re: PC speaker gives incorrect results (when low and high pass filtered) and with 8088 MPH?

Posted on 2016-03-02, 17:06

by superfury

in PC Emulation

But the 72 samples is actually the frequency response time? It's the amount of samples from the PIT that actually move the cone from 0 to 1, or from 1 to 0, in that time. When you send samples faster than that, you will move the cone too less, sending it slower will move it too much.

Re: PC speaker gives incorrect results (when low and high pass filtered) and with 8088 MPH?

Posted on 2016-03-02, 15:59

by superfury

in PC Emulation

Also, yes, PWM itself can be at any frequency, it's simply longer and shorter duty cycles seperately programmable. But the PC speaker response(only moving a bit while getting 1 or 0, moving towards that value, is what makes the magic happen. If you execute a PWM slower than the frequency response(~ …

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Re: 8086 average clocks per instruction (when running normally)?

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Re: x86EMU emulator releases

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Re: PIT emulation gives incorrect results with 8088 MPH's credits?

Re: PC speaker gives incorrect results (when low and high pass filtered) and with 8088 MPH?

Re: PC speaker gives incorrect results (when low and high pass filtered) and with 8088 MPH?

Re: PC speaker gives incorrect results (when low and high pass filtered) and with 8088 MPH?

Re: PC speaker gives incorrect results (when low and high pass filtered) and with 8088 MPH?