Re: How does Lemmings (for DOS) do in-frame palette switching?

Posted on 2017-12-05, 13:22

by

by Scali

in Marvin \ Video

in Marvin \ Video

derSammler wrote: No, it's used in the entire game. See http://www.mobygames.com/game/dos/california- … mes/screenshots (screenshots marked with CGA "MORE-color" mode). Ah yes, seems you're right! For some reason I only ever saw the footbag part in extra colours.

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Re: Is worth DOS programming in these days?

Posted on 2017-12-05, 13:18

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by Scali

in Marvin \ Software

in Marvin \ Software

But it also looks a little boring, so you may after all want to go dos and have to write a more interesting-looking wobbly integer renderer. The real challenge is to write wobble-free integer renderers in DOS. That is what originally got me started on the Just keeping it real-series of blogs: I …

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Re: How does Lemmings (for DOS) do in-frame palette switching?

Posted on 2017-12-05, 12:55

by

by Scali

in Marvin \ Video

in Marvin \ Video

That's because for CGA, it only works at 4.77 MHz and even then is very complicated. CGA is actually simpler than EGA/VGA, because CGA is synchronized to the PIT. You won't have to re-set the PIT every frame, because you know that a CGA frame is exactly 19912 PIT ticks at all time. 8088 MPH …

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Re: Problems with AM386DX-40 chip

Posted on 2017-12-05, 01:05

by

by Scali

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Motherboards from that era were hardwired for a single clockspeed. You can clearly see a 66 MHz crystal installed there. This is divided by 2 to generate the 33 MHz clock. This crystal has to be replaced by an 80 MHz one to make the CPU run at 40 MHz (but I can't guarantee that it will work properly …

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Re: CVX-2 : covox adapter

Posted on 2017-12-04, 22:36

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

My reasoning just was that the plug has so high impedance output so it really needs an amplifier and it comes with it so it forms a complete system. True, you really want a preamp close to the Covox for best results. I have not seen the adverts so I just don't know if it was ever advertised to be …

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Re: CVX-2 : covox adapter

Posted on 2017-12-04, 21:33

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

But wasn't the Covox a complete system with amplified speaker, so shouldn't it be taken as a whole? I don't see why really. Many early sound cards were sold as complete kits with (cheap) speaker kits. I don't think anyone ever argued that the speakers need to be included for the overall quality of …

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Re: CVX-2 : covox adapter

Posted on 2017-12-03, 21:26

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

Yeah, but has anyone tested to see what the actual cut off for the frequency range for the R-2-R covox is? Can it actually output a 22.05 KHz frequency? The Covox has no filter at all (and the CVX4 also has a no-filter setting). So theoretically there is no cutoff. I think the easiest way to verify …

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Re: CVX-2 : covox adapter

Posted on 2017-12-03, 21:13

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

I don't honestly remember the calculation, but given the design of the R-2-R covox I remember someone calculated that the frequency range for it topped out somewhere around 7 or 8 KHz. Are you sure you're not confusing the Covox with the DSS? The example recordings at 44.1 kHz with the CVX4 should …

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Re: CVX-2 : covox adapter

Posted on 2017-12-03, 19:18

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

Paralel wrote: It has roughly double the frequency range of the discreet R-2-R ladder Covox design What makes you say that? Technically, the only limit for the frequency range of a Covox is the speed at which the CPU can bang out the samples through the printer port.

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Re: CVX-2 : covox adapter

Posted on 2017-12-03, 18:29

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

why not use Resistor Networks ? less pain to solder :) The goal of the CVX4 is to sound as good or better than the original Covox. I suppose we'd need to have some prototypes first with resistor networks, before we can decide whether or not they are an accurate replacement for the discrete …

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Re: CVX-2 : covox adapter

Posted on 2017-12-01, 22:35

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

CVX4 got mentioned on Adafruit! https://blog.adafruit.com/2017/12/01/cvx4-par … ch-thing-clone/

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Re: Maximum amount of memory on a 486

Posted on 2017-12-01, 14:50

by

by Scali

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I'll have to check my Compaq Deskpro XL466. It's a very late 486, with PCI and 72-pin DIMMs and all. It's also very high-end (workstation-class), with onboard LAN and SCSI. I wonder how much memory that one could take. Here's a Russian page on it with good pictures: http://ru.pc-history.com/compaq- …

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Re: Some 8088 Portable Love

Posted on 2017-12-01, 11:16

by

by Scali

in Marvin \ System Specs

in Marvin \ System Specs

Strange that it reports an 8Mhz V20, yet the benchmark shows it being the same as a 4.77Mhz 8088. Well, I don't know about V20s, but perhaps it is possible to detect the speed rating of them in some way. So it might detect that the CPU is rated for 8 MHz, even though it is running at 4.77 MHz ( …

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Re: Fastest "Turbo XT"

Posted on 2017-12-01, 11:12

by

by Scali

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

As far as I know, officially there are no 8088 or V20 CPUs that are rated higher than 10 MHz. There are HL variants of V20 and V30 rated up to 16MHz. It seems you are right, here is the datasheet (I had only looked at the regular V20 before): http://html.alldatasheet.com/html-pdf/162440/NEC/ …

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Re: CVX-2 : covox adapter

Posted on 2017-11-30, 22:25

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

Mouser does seem to have these, sold separately: https://eu.mouser.com/ProductDetail/Bou ... ent=Bourns

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Re: Fastest "Turbo XT"

Posted on 2017-11-30, 20:26

by

by Scali

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

As far as I know, officially there are no 8088 or V20 CPUs that are rated higher than 10 MHz. The fastest 'common' variation of turbo XTs is 9.54 MHz (double that of the original PC). I do vaguely recall however that there were some 'factory-overclocked' XT clones of 12 or 12.5 MHz. But I can't name …

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Re: EGA DOS benchmarks?

Posted on 2017-11-30, 12:49

by

by Scali

in Marvin \ Video

in Marvin \ Video

Strictly speaking, there is no such thing as a CGA monitor. The 5153 is a color monitor with digital RGBI input. Restrictions of CGA don't apply, as those come from the video memory limitations of the CGA card, not from the monitor. EGA works, since it is using digital RGBI as well. Only modes with …

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Re: Some 8088 Portable Love

Posted on 2017-11-29, 22:48

by

by Scali

in Marvin \ System Specs

in Marvin \ System Specs

Obvious question is of course: But will it run 8088 MPH? 😀

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Re: Would an FPGA-based "universal" sound card be technically feasible?

Posted on 2017-11-29, 21:41

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

I think part of the 'charm' of the SID, especially the 6581 models, is a direct result of the manufacturing technology. Since the chip is largely analog, the circuit directly affects how the chip sounds. Poor consistency in manufacturing meant that individual 6581s can vary quite a bit in sound. The …

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Re: CVX-2 : covox adapter

Posted on 2017-11-29, 21:32

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by Scali

in Marvin \ Sound

in Marvin \ Sound

I think that would be good, except the minimum order is ten thousand because most suppliers don't have these in stock and they have to place order to a factory. I think Jameco was able to sell some R2R-104 devices in multiples of five. I couldn't find any on Jameco, but some googling found me this: …

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