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

Posted on 2016-03-10, 08:12

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by reenigne

in PC Emulation

in PC Emulation

I don't think there's any sensible way to measure the timing of this instruction that doesn't give 19 cycles on 8088 - if there's an offset between the "I" and when the instruction decoding happens, it'll be the same for all instructions, so will be cancelled out when measuring "I to I". Which …

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Re: CGA Timings

Posted on 2016-03-09, 19:07

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by reenigne

in PC Emulation

in PC Emulation

Ah yes, the same can also be said for hsync I suppose. If you set a hsync width of 16, that is not the hsync pulse alone, but the whole period of horizontal blank, front porch, hsync pulse, back porch, and the colorburst. Right. The actual hsync pulse sent to the monitor starts 32 hdots after the …

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Re: 808x and prefetch

Posted on 2016-03-09, 18:03

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by reenigne

in PC Emulation

in PC Emulation

For IBM CGA, the wait state for accessing (read or write) video RAM is computed by doing this: * wait 8 hdots (one hdot is 1/3 of a CPU cycle) * wait for the next 16 hdot boundary * wait for the next CPU cycle To a first approximation, the resulting wait state is between 3 and 8 CPU cycles (the 3 …

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Re: CGA Timings

Posted on 2016-03-09, 17:43

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by reenigne

in PC Emulation

in PC Emulation

Vertical sync position should also be adjusted by one Minor correction - vsync position is not adjusted, so vsync starts on scanline 224. It doesn't make a lot of difference for most purposes, but I do have some code which messes with CRTC registers in the vicinity of the vsync and may confuse the …

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

Posted on 2016-03-09, 17:24

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by reenigne

in PC Emulation

in PC Emulation

Seems I should pop in here more often - I've been missing an interesting conversation! Glad to see other people are thinking about and working on this stuff. For comparison, here's what my bus sniffer outputs for a far jump instruction with the prefetch queue initially filled: 20FFF .p... 00F1D FF …

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Re: 8088 MPH: We Break All Your Emulators

Posted on 2016-03-01, 22:49

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by reenigne

in PC Emulation

in PC Emulation

I've given some thought to related problems. The trouble with using the PC speaker for output is that there is no DMA, so you have to send the samples to the PIT yourself at regular intervals. One way to run some code at regular intervals is to use the timer interrupt. That works great, except for …

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Re: 8088 MPH: We Break All Your Emulators

Posted on 2016-02-29, 18:35

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by reenigne

in PC Emulation

in PC Emulation

Not that I know of. I don't think that poking at CGA registers would make a very good torture test for VGA emulation, though.

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Re: 8088 MPH: We Break All Your Emulators

Posted on 2016-02-25, 13:34

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by reenigne

in PC Emulation

in PC Emulation

Makes me wonder, is there a way to make the 'critical window' more robust? As in, you give it 1 or 2 extra scanlines, and move to a polling strategy to re-sync to the hsync, or something to that effect? Maybe... I don't have any way to test such a thing, though. You know where the source code is - …

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Re: 8088 MPH: We Break All Your Emulators

Posted on 2016-02-25, 09:47

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by reenigne

in PC Emulation

in PC Emulation

I wonder if that means that adding a tiny bit of delay at the start of a frame will make it work properly on a clone as well. I don't think it would. The effect may appear to be "nearly" correct on clones but the timing is still off and in this effect, being off by a small amount has knock-on …

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Re: 8088 MPH: We Break All Your Emulators

Posted on 2016-02-24, 18:41

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by reenigne

in PC Emulation

in PC Emulation

I haven't written up the information about the cycle counts yet - I have a lot more experiments to do first. I think the reason DI takes 1 cycle more is that it needs to set an internal flag in the CPU to use ES instead of DS. As for why this doesn't happen with CMP - I think it's masked by the fact …

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Re: 8088 MPH and emulation....

Posted on 2015-10-18, 18:13

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by reenigne

in PC Emulation

in PC Emulation

Ah yes, I suppose the Moire effect ran, but just never exited? I think it was just exiting immediately (i.e. AL had the opposite value in PCEm-X than on a V20). From https://www.youtube.com/watch?v=Vg2n8Fp7F2g (made before the SALC fix) it looks like the polygons, Kefrens and credits aren't working …

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Re: CGA Composite Mode under DOSBOX (Commited r3804)

Posted on 2015-10-04, 17:28

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by reenigne

in DOSBox Patches

in DOSBox Patches

Since you previously mentioned the possibility of adding comb filtering, the title screen in Sierra Championship Boxing would greatly benefit from it. The gray road looks rather ridiculous without comb filtering. The back of the box screenshot indicates that Composite is indeed the game's intended …

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Re: CGA Composite Mode under DOSBOX (Commited r3804)

Posted on 2015-10-03, 20:29

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by reenigne

in DOSBox Patches

in DOSBox Patches

MAJOR 3-MONTH NECROBUMP , but has there been any minor or major progress since last post in this thread? Unfortunately not. I do indeed have plans, but this hasn't been high on the list lately. Actually in the last few days I picked up the project of building the device I need to gather the data …

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Re: 85 colors on a Tandy 1000SX

Posted on 2015-09-05, 12:20

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by reenigne

in Milliways

in Milliways

...still looks interlaced in the video footage for whatever reason... :B There's a good reason for that. The image is created by rapidly flickering between two images (at 30Hz). Flicker is more noticeable if you're flickering between a dark image and a light image. So instead of doing that, Chris …

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Re: 8088 MPH: We Break All Your Emulators

Posted on 2015-08-03, 15:43

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by reenigne

in PC Emulation

in PC Emulation

I ran the demo again, and on the calibration screen I finally noticed the "Space: CGA model [old]" I just didn't realize that I had to hit the Spacebar to get new CGA colors. I had assumed that the program would pick the proper color palette because it autodetected my cards correctly. Ha! I guess …

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Re: 8088 MPH: We Break All Your Emulators

Posted on 2015-08-03, 09:46

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by reenigne

in PC Emulation

in PC Emulation

You could avoid the overhead by precalculating the sample waveform values with loudness mapping so you don't have to do it at runtime in the playing/mixing routine. Yes, we could do that but it would introduce more distortion for a given loudness increase than doing it on the mixed waveform. …

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Re: 8088 MPH: We Break All Your Emulators

Posted on 2015-08-03, 08:23

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by reenigne

in PC Emulation

in PC Emulation

I spotted a greet from reenigne to the SRCS in the end credits. I should really check SRCS out sometime since I live in the area (although almost an hour away); I probably don't have anything exciting to bring myself, though, except for a modest collection of early '90s video/audio cards and MS-DOS …

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Re: 8088 MPH: We Break All Your Emulators

Posted on 2015-08-01, 06:50

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by reenigne

in PC Emulation

in PC Emulation

Hornet, CRTC and DESiRE are pleased to announce a final version of 8088 MPH which can be downloaded at http://www.reenigne.org/8088MPH_final.ZIP . Also a capture of the final version can be seen and heard at https://www.youtube.com/watch?v=hNRO7lno_DM . This final version has some new graphics, …

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Re: Host machine unresponsive when debugging

Posted on 2015-07-17, 14:14

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by reenigne

in DOSBox Development

in DOSBox Development

Oh, cool! Thanks for that, it saves me a lot of work!

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Re: Host machine unresponsive when debugging

Posted on 2015-07-17, 07:52

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by reenigne

in DOSBox Development

in DOSBox Development

I think I've got to the bottom of this now, so I'm adding the information here in case anyone else needs it. The call stack when the machine becomes unresponsive is: dinput.dll!_CDIDev_Acquire@4() Unknown SDL.dll!DX5_DInputInit(SDL_VideoDevice * this) Line 238 C SDL.dll!DX5_CreateWindow(SDL_ …

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