Re: Fixing a DTK PTM-1230C

Posted on 2020-05-16, 16:16

by

by derSammler

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The 14 MHz one is always there. If the CPU is 12 MHz, the main crystal should be 25 MHz (12.5 MHz is the resulting speed for these CPUs). The third one is not needed and only for the FPU. It's optional.

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Re: Compaq OEM Voodoo 3 3500 AGP with only VGA and TV-Out... lets put this to rest.

Posted on 2020-05-16, 12:28

by

by derSammler

in Marvin \ Video

in Marvin \ Video

I was expecting that no one would read the sentence directly after that, so I removed the whole paragraph. I have a whole box of cards to prove that. But nevermind, that leads nowhere. It's an OEM card, not more - not less.

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Re: "Best" sound card for an old ATARI 286 PC?

Posted on 2020-05-16, 10:15

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by derSammler

in Marvin \ Sound

in Marvin \ Sound

Doesn't seem like the topic starter will ever come back to read all the recommendations.

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Re: Modern PSU for Pentium 3 what 5V xxA ?

Posted on 2020-05-16, 10:13

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by derSammler

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I always thought the issue with newer PSUs isn't that the 5V rail is weak, but that the 12V rail is used for regulation, which is normally not much loaded on older systems, thus making the 5V unstable or out-of-spec?

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Re: Pentium "Sweet Spot"

Posted on 2020-05-16, 10:10

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by derSammler

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

200 or 233 MHz MMX. You need that speed to really use the 3dfx (once had one in a P133, and it wasn't much fun), and the P55C is also better to slow-down than the non-MMX Pentiums.

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Re: Sound Blaster: From IRQ7 to IRQ5, when and why?

Posted on 2020-05-16, 10:07

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by derSammler

in Marvin \ Sound

in Marvin \ Sound

That would only work if every interrupt handler would be written that way. But since IRQ/DMA sharing was not part of the ISA specs, no interrupt handler works this way. Instead, you get a race condition and when interrupt handler (a) is executed but hardware (b) raised it, the system will freeze, as …

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Re: Compaq OEM Voodoo 3 3500 AGP with only VGA and TV-Out... lets put this to rest.

Posted on 2020-05-16, 08:49

by

by derSammler

in Marvin \ Video

in Marvin \ Video

Yeah it seems pretty straightforward to me but apparently some people question it... not exactly sure why. I think the silver heatsink makes people think it shouldn't be called a 3500. Afaik it was all about their existence as retail, not OEM. These cards were made for Compaq and no one could just …

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Re: My New Compaq Presario 425

Posted on 2020-05-16, 08:20

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by derSammler

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

You should definitely report this to Fedex, this isn't something normal. They won't care, because it's not their fault. You can clearly see on the third picture that the packaging was completely insufficient for shipping such a thing. Some bubble wrap and almost no clearance between the item and …

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Re: Switching video card when switching OS.

Posted on 2020-05-15, 19:10

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by derSammler

in Marvin \ Video

in Marvin \ Video

Then look here: https://www.amazon.com/s?k=vga+switch+box&ref=nb_sb_noss_2

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Re: Switching video card when switching OS.

Posted on 2020-05-15, 18:59

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by derSammler

in Marvin \ Video

in Marvin \ Video

Of course, there are video input switchers. But the more easy solution would be to connect one card via VGA and one via DVI. You normally have both on most non-CRT monitors anyway.

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Re: Switching video card when switching OS.

Posted on 2020-05-15, 18:49

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by derSammler

in Marvin \ Video

in Marvin \ Video

Yes, that's possible. In device manager, select that the card is not available in all hardware profiles and then select that it is disabled in this hardware profile. On the second OS, do the same with the other card. Works fine, did that in one of my builds, too. Only drawback is that you get a …

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Re: Bought these (retro) hardware today

Posted on 2020-05-15, 15:28

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by derSammler

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It was sold as working, so the seller lied about its condition. I don't see a conflict here. You are not supposed having to repair something that was sold as working - even if you can and have the tools/knowledge to do so.

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Re: Sound Blaster: From IRQ7 to IRQ5, when and why?

Posted on 2020-05-15, 13:18

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by derSammler

in Marvin \ Sound

in Marvin \ Sound

Just guessing, but maybe the rise of Windows, which allowed printing in the background. With the sound card on IRQ 7, playing any sound would have frozen the system while a print job was running. But again, just guessing. Makes sense to me, however.

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Re: Leading Technology 5500AT 286 Project

Posted on 2020-05-15, 12:27

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by derSammler

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Check the BIOS. Most 286 only allow running the bus with either full speed or 1/2 speed. With some luck, there's an 1/3 option. It is my understanding that the clock will either be half or 66% of the original, but I'm not sure with board. A 287 is driven with 2/3 of the CPU speed, unless you install …

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Re: MICROSOFT MACH 10 - 8086 upgrade for 8088 - missing parts

Posted on 2020-05-15, 12:01

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by derSammler

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Judging from the look of the caps, these are standard tantalum caps with either 47 or 100uF at 16V. 47uF is more likely, but you can use either. Q1 is a simple pnp transistor.

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Re: Hyper386sx 286 Upgrade CPU

Posted on 2020-05-15, 11:10

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by derSammler

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

1. link: 13 years old, no pictures, just someone claiming something. Probably didn't even meant PGA, as I don't see how these were ever hard to find. 2. link: someone saying "shoud be the same". No outcome. Anyway, this PLCC-to-PGA was a huge thing some years ago in the Amiga community. People …

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Re: Bought these (retro) hardware today

Posted on 2020-05-15, 10:59

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by derSammler

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

From my understanding the current will flow the reverse way when exchanging VCC and GND? No, since a transistor can not have the current flow the other way - it will block it. And early, simple CPUs like the V20 are made of transistors only. The CPU may get warm since some leaking current still …

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Re: Hyper386sx 286 Upgrade CPU

Posted on 2020-05-15, 09:49

by

by derSammler

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

You need an adapter for this. You can not replace a PGA socket with a PLCC socket by just replacing it. Their pin-out does not match. Google for "replace pga with plcc socket" if you don't believe it - there are even companies specialized in making such adapters.

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Re: Bought these (retro) hardware today

Posted on 2020-05-15, 09:45

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by derSammler

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

With these CPUs, not even the CPU itself will die. It only has a single GND and VCC pin, which are swapped when the CPU is inserted the wrong way. No current will flow in this case and no short is caused either. The board was probably dead from the outset.

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Re: What retro activity did you get up to today?

Posted on 2020-05-15, 09:15

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by derSammler

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

About to finish that once-poor PlayStation 2. IMG_20200515_110416706.jpg Had to re-align parts of the drive mechanism to get rid of odd sounds during seeks. The sled was slipping off the screw drive. Tested all kinds of media and it works as new. :) Now I have to find out why the disc tray does not …

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