Re: Emulating Area5150

Posted on 7 minutes ago

by

by Scali

in PC Emulation

in PC Emulation

The GPU is used for scaling the buffer to the window and compositing the GUI debug windows, but not much else at the moment. I eventually want to have a few shaders available for post-processing effects. (CRT emulation, color/geometry adjustments, etc) Okay, that should be trivial enough that there …

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Re: Unknown card: Cambridge Research Systems AS-1.

Posted on Yesterday, 23:52

by

by Scali

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Looks like they're still around: https://www.crsltd.com/how-to-contact-us/about-us/ And that supports Deunan's guess that it's some kind of scientific data acquisition or control card. Perhaps drop them a line and ask if they can tell you what it is? They may still have documentation on it, or …

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Re: Emulating Area5150

Posted on Yesterday, 22:00

by

by Scali

in PC Emulation

in PC Emulation

I've made an initial Windows release of my emulator, available here: https://github.com/dbalsom/martypc/releases/ Interested to see what people think. I'm open to suggestions and feature requests! I've tried it on two machines around here... one is a desktop Core i7 860 with a GeForce 970. The …

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Re: CGA Cursor Hiding

Posted on 2023-05-31, 13:29

by

by Scali

in PC Emulation

in PC Emulation

I believe you need to set bit 5 of the Cursor Start register to 1, and bit 6 to 0 to hide the cursor: http://bitsavers.trailing-edge.com/components … Sheets/6845.pdf

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Re: GloriousCow's PC Emulation Blog

Posted on 2023-05-30, 07:06

by

by Scali

in PC Emulation

in PC Emulation

Great work! These blogs explain exactly what I've always been so critical about regarding PC emulators: Firstly, cycle-exactness matters. Secondly, cycle-exactness does not stop with the CPU alone. The CPU does not operate in a vacuum. It interacts with other devices on the bus, so any externally …

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Re: Pulling my hair out with EGA programming.

Posted on 2023-05-28, 21:50

by

by Scali

in Marvin \ Video

in Marvin \ Video

I'm not exactly sure what's going on in that assembler code. What is the purpose of xor di, di ? XOR stands for Exclusive-Or. It's a bitwise operator. This is a simple trick: when you bitwise-xor any value with itself, the result is always 0. It's a slightly fancier version of sub di, di ( …

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Re: The Joy of MMX

Posted on 2023-05-28, 09:26

by

by Scali

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I think there are two things here: 1) Intel may have used shady marketing for MMX/SSE 2) MMX/SSE may or may not be valid technologies of themselves As for 2), as I already said, MMX had its applications. I've written my share of hand-optimized MMX back in the day. It's just that around the same time …

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Re: The Joy of MMX

Posted on 2023-05-27, 14:49

by

by Scali

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

MMX was great for image processing. Scaling/filtering bitmaps, texturing triangles and whatnot. It was also useful for certain parts of video decoding. But it came a bit too late, as videocards were taking over these tasks.

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Re: Did early sound cards actually process all the sound effects?

Posted on 2023-05-27, 09:04

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

The channels don't run purely asynchronously to each other either, the base timing comes from a freq related to video chipset and everything the chip does is a division of that. I don't know exact timings though, my familiarity with Amiga at low level is lacking compared to some of the other …

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Re: The Joy of MMX

Posted on 2023-05-26, 18:25

by

by Scali

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Strange, I remember using a P2 on a thinkpad. But they weren't necessarily good for battery life! But it's quite typical that the mobile processors were the previous gen at low voltage and die shrunk. They didn't push them for desktop systems, which is why I didn't know anyone really making builds …

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Re: Did early sound cards actually process all the sound effects?

Posted on 2023-05-26, 18:19

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

What about video cards? I understand all graphics in DOS were processed by the CPU, and the video cards were just more or less dummy frame buffers and the only difference in speed were due to different bus speeds and memory speeds? This is vs modern GPUs that offload most of the rendering from the …

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Re: The Joy of MMX

Posted on 2023-05-26, 16:42

by

by Scali

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The Serpent Rider wrote on 2023-05-26, 16:20: Even regular PMMX 233 can work at 100 MHz FSB and 250 MHz, which noticeably improves experience. True, you can run them at these settings, but then you're overclocking. There is no official support for these settings, unlike with the clones.

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Re: Did early sound cards actually process all the sound effects?

Posted on 2023-05-26, 16:39

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

Sound Blasters did support decompressing of 4-Bit PCM streams, I vaguely remember. Yes, the 'DSP' on an Sound Blaster was a simple microcontroller (Intel 8051). The microcontroller had an internal timer which timed when to output the next sample to the DAC, which made DMA-based PCM playback …

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Re: Did early sound cards actually process all the sound effects?

Posted on 2023-05-26, 15:30

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

In reality all this sound processing didn't "move to the cpu". More accurately, all sound became PCM with some mixing in the CPU, and real-time sound generation became a thing of the past. Exactly, that 'all sound became PCM' is the key here. PCM, let's say 'digital audio' wasn't the standard …

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Re: The Joy of MMX

Posted on 2023-05-26, 14:07

by

by Scali

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Not really. It's optimized and has larger caches. So in general it's faster than the non-MMX version. I didn't say it was slower in general. I just said that some instructions have an extra cycle of latency because the pipeline is 6 stages instead of 5 on the regular Pentium. But yes, I forgot to …

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Re: The Joy of MMX

Posted on 2023-05-26, 13:35

by

by Scali

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Pentium MMX is pretty much exactly what the name implies: a standard in-order Pentium CPU, with MMX instructions added. However, because of the extra instructions, the decoding pipeline had to be modified somewhat, which makes certain operations 1 cycle slower than they were on a Pentium classic. On …

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Re: Emulating Area5150

Posted on 2023-05-26, 09:31

by

by Scali

in PC Emulation

in PC Emulation

Speaking of releases, how would you feel about me possibly including 8088MPH/Area 5150 with my binary release? My thoughts were it would be great to give people a way to experience the demos as intended themselves "out of the box", but I completely understand if you'd rather not have it distributed …

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Re: Emulating Area5150

Posted on 2023-05-25, 14:04

by

by Scali

in PC Emulation

in PC Emulation

It didn't start out that way, I kept trying to derive effective resolution from the CRTC registers and I constantly ran into issues in 8088MPH dealing with the logic for it. I think I saw this very advice from either you or Scali on here Ah yes, VileR and myself are the OG overscan/border …

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Re: Serdashop MIDI Card, IRQ 2, and the 8259a

Posted on 2023-05-24, 09:08

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

Oh! So I should set the card to IRQ9 and expect that software will find it on IRQ2? There is no IRQ9 on the ISA bus. It's just that IRQ2 technically goes to IRQ9 on an AT (which is why documentation often speaks of 'IRQ2/9') IRQ0 (8253 timer), IRQ1 (keyboard), IRQ8 (CMOS timer) and IRQ9 (IRQ2 line …

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Re: Serdashop MIDI Card, IRQ 2, and the 8259a

Posted on 2023-05-23, 21:44

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

The 8259a is a secondary cache controller, I think. The 8259A is the Programmable Interrupt Controller: https://en.wikipedia.org/wiki/Intel_8259 On AT and compatible systems, there are two 8259s, which are connected together ('cascaded'). This means that the second 8259 is connected to IRQ2 on the …

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