Re: Are you missing -5volt too?

Posted on 2016-10-23, 07:07

by

by Jepael

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Yes the circuit you posted is already a power supply itself. It has an AC transformer so it takes mains AC in and steps it down and isolates to safe low voltage levels. The diode bridges rectify the AC into ripply pulses of one polarity which is smoothed to ripply DC with the cap. So again in this …

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Re: Are you missing -5volt too?

Posted on 2016-10-22, 21:27

by

by Jepael

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

That is a l7905acv. According to what I can find online, it used negative 12 volt and not positive 12 volt as input. As -12v rails do not provide enough milliamp, I really need to be able to draw somewhat 500 milliamp from positive 12volt. I guess the ISA slot solution is a simple one, taken …

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Re: Are you missing -5volt too?

Posted on 2016-10-22, 19:55

by

by Jepael

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Most AT power supplies had 0.3A max output from -5V anyway, and -12V outputs at about 0.5A to 0.8A. How much would anyone need -5V for sound cards, 100mA or 200mA tops maybe? The 7905 in TO220 case generating -5V from -12V would be perfect for that job, as long as it has ceramic bypass caps, some …

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Re: x86 Exceptions vs normal interrupts error code?

Posted on 2016-10-22, 19:02

by

by Jepael

in PC Emulation

in PC Emulation

How does software detect if it needs to pop an error code(used in some exceptions) from the stack(vs normal INT instruction)> Why do you need to worry about this, do you have some example situation where this is necessary? Because otherwise the software writer knows what the software currently …

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Re: Are you missing -5volt too?

Posted on 2016-10-22, 12:47

by

by Jepael

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

an lm337 with a couple of resistors + caps will give up a -5v 1.5A output. or chain an 905 (ie: MC7905BTG) and that will give you a direct -5V / 1A output. should cost < 2$ all up or something. I have seen that online somewere too... The problem now, is that I can get -5volt output, the problem is …

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Re: How to stop 'computer thinking' noise?

Posted on 2016-10-19, 18:21

by

by Jepael

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Actually, I study electronic engineering but I'm a freshman, Calculus and basic Physics are my food right now although electronics was my hobby for many years prior to university, so I'm in no position to ask for anything yet. I traced the the rout of YMF262 -> YAC512 -> 3403 -> Mixer. YAC512 3403 …

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Re: A solution to compact flash IDE (CF-IDE) floppy drive problems

Posted on 2016-10-19, 15:45

by

by Jepael

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

does not surprise me CF cards driving bit 7 because the CF spec lets you bitbang CF cards as 8bit IO as IDE!... which is probably how all the cf-ide interfaces are working as, just bit banging 8bit io. all these CF adapters are 'dumb' they just map the IO lines, they dont have IC's to interface …

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Re: A solution to compact flash IDE (CF-IDE) floppy drive problems

Posted on 2016-10-18, 20:55

by

by Jepael

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

That's not the problem, at least not on my two 486 test PCs. In both cases the IDE and floppy adapters are built into the same VL-Bus adapter. In one case they are built into the motherboard. And these PCs do not exhibit the problem when using their original IDE hard drives. If they did they'd …

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Re: A solution to compact flash IDE (CF-IDE) floppy drive problems

Posted on 2016-10-18, 19:08

by

by Jepael

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The problem is because both IDE and floppy would like to exist at address 3F7h. It is same with hard drives, not just CF cards. The CF-IDE adapters themselves can't cause the issue. See http://www.intel.com/design/archives/periphrl/docs/7225.htm for more info. When you have a combo adapter with IDE+ …

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Re: PC Emulation: Adaptec 1540

Posted on 2016-10-18, 07:25

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by Jepael

in PC Emulation

in PC Emulation

Well the card specs and manuals say it uses DMA channels to transfer data so that must be it. I don't know which chip is used on 1540 adapter so I have no datasheet to look at.

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Re: Implementing 80286 cycle timings in UniPCemu?

Posted on 2016-10-15, 20:13

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by Jepael

in PC Emulation

in PC Emulation

The instruction set summary starts from page 47, the comments are explained on page 46.

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Re: Don't you love it when the manual is wrong?

Posted on 2016-10-15, 13:02

by

by Jepael

in Milliways

in Milliways

Actually what manual says is that max vertical rate is 140Hz and max horizontal rate is 96 kHz. So it just can't go over 85Hz at 1280x1024, and over 75 Hz at 1600x1200 resolution, because that would go over the 96 kHz hfreq limit. Therefore, 1024x768 @ 100 Hz (81kHz hfreq, 113 MHz pixel clock) is …

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Re: Aztech Sound Galaxy Basic/Pro 16 - what are the two green wires between the codec chip and the mixer chip?

Posted on 2016-10-13, 18:58

by

by Jepael

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Could a bad capacitor lead to "filtered" output? If so, which one(s) could most likely be the culprits? It could, but it's just more likely it just has less treble by design, because of the mixer chip settings or component values in the audio paths. If there's no data on the mixer chip, we can't …

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Re: IBM PC AT BIOS floppy and keyboard errors and XT-IDE BIOS not fully booting on UniPCemu's 286 emulation?

Posted on 2016-10-13, 17:45

by

by Jepael

in PC Emulation

in PC Emulation

Well, my main point was, since the SQW and CKOUT outputs are not used (they are not connected to anything), so does it really make sense to use host CPU resources to simulate unused stuff? (Simulating it in hardware like FPGA would come almost free so there could be a debug output for that...) Since …

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Re: Aztech Sound Galaxy Basic/Pro 16 - what are the two green wires between the codec chip and the mixer chip?

Posted on 2016-10-13, 15:40

by

by Jepael

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Nothing regarding filtering. It looks like those are read strobe (RDn) and chip select (CSn) pins, but frankly the picture is not so good as it looks like the other green wire is not directly connected to AD chip. So perhaps they had CS and RD accidentally swapped so they had to mod it, and either …

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Re: IBM PC AT BIOS floppy and keyboard errors and XT-IDE BIOS not fully booting on UniPCemu's 286 emulation?

Posted on 2016-10-13, 14:29

by

by Jepael

in PC Emulation

in PC Emulation

But the time, like on the wall, runs at 1Hz, but the periodic interrupt can be set at a rate up to 32 kHz with something called a 22-stage divider? Not on a PC, because it runs at 32kHz crystal, you can't reach 32kHz periodic interrupt rate. (The datasheet would tell the timings and how it works …

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Re: IBM PC AT BIOS floppy and keyboard errors and XT-IDE BIOS not fully booting on UniPCemu's 286 emulation?

Posted on 2016-10-12, 19:15

by

by Jepael

in PC Emulation

in PC Emulation

Looking at the log, it seems the RTC timer times out immediately after a STI instruction is executed? How does timing on a real CMOS chip work? Is it simply a counter that's counting down from the value set, or does it count up until it gets at the value set, which then resets and fires an IRQ8? …

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Re: I've an idea: Let's get some game development going

Posted on 2016-10-11, 15:24

by

by Jepael

in Milliways

in Milliways

Those older racing games may have large areas of single color. Those areas can be written quite fast, 8 same-coloured pixels in a single byte write in 16-color mode. There are few different write modes in EGA/VGA cards and one would choose the write mode based on what would be the fastest way to …

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Re: DOS 7.1 will only partition 8GB CF card

Posted on 2016-10-11, 14:57

by

by Jepael

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Oh great. The seller I bought it from has negative feedback with fake CF cards. I never thought to look because there was a lot of positive feedback. And I've already left feedback so I can't even warn them. Remember it might not be the cards fault. For example Kingston says that their CF cards …

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Re: Computer is in power off state but is actually in power on state

Posted on 2016-10-07, 18:27

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by Jepael

in Milliways

in Milliways

The computer works flawlessly while powered on, the only problem is that it does not want to power on after being shut down (the only exception is the super flower psu that powers it on even than). Remove bios battery and try again. Change to new battery. Sometimes funny things happen when they are …

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