Re: XT IDE DIY card

Posted on 2022-02-25, 10:37

by

by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Sphere, Half of the fun is ordering the PCB, waiting 4 weeks, ordering the parts, burning them while soldering, fitting some the wrong way etc! :D Otherwise it's boring! :D SMD appeals me - gives me some opportunity to do SMD soldering. I have no problem with that. It's just that the project seems a …

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Re: Keyboard crashes on old 386 motherboard

Posted on 2022-02-24, 18:22

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by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

finally, OE pin on CPU 245. Filename SDS00014.png File size 14.79 KiB Views 60 views

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Re: Keyboard crashes on old 386 motherboard

Posted on 2022-02-24, 18:16

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by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

More tests done. Voltages are ok across the board. I connected channel 1 directly to the 5V from PSU and I was probing with channel B which was overlaid on channel 1. No difference. Voltage is 4.85 everywhere. More tests: 1. The wonky BUS is present with no cards connected 2. The data line on the …

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XT IDE DIY card

Posted on 2022-02-24, 12:16

by

by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Hi there, I'd like to make my own XT-IDE card, I see a few projects online, does someone have any recommendation to which one to go for? I like this one http://dangerousprototypes.com/docs/XT_IDE_disk_controller but I don't see much activity around it. Otherwise I see this one: https://www. …

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Re: Keyboard crashes on old 386 motherboard

Posted on 2022-02-24, 10:08

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by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

time to get a XT IDE card I guess! 😀 Two birds with one stone. I'll check with no ISA controller first, if I see the same "weak" signals, then I am at a loss to be honest. I'll also check the signals coming from the CPU - even though they go through the 245 so it shouldn't matter.

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Re: Keyboard crashes on old 386 motherboard

Posted on 2022-02-23, 23:22

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by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Another update. I swapped the KBC chip 245: no change. I checked the resistor packs we talked about, I found the one which is connected to the 8bit data lines. All seems to be ok. It's not on the last slot though? I measured 10KOhm between each leg and the common pin and 0.7KOhm between the common …

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Re: Keyboard crashes on old 386 motherboard

Posted on 2022-02-17, 22:58

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by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I've checked again and I was indeed mistaken. The T/R line (cyan above) is indeed active (ie it changes status low/high regularly). However, the OE line is tied to ground, hence always low and hence the chip is always active. so at this point none of my readings I posted were in Z state.

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Re: Keyboard crashes on old 386 motherboard

Posted on 2022-02-17, 16:52

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by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Thank you It's a 200Mhz 4ch scope so yes, a nice little thing! :) I checked pin 1 and it's always high, I guess it's normal for a keyboard to be "one way only"? Cyan trace on the first picture is pin 19 to show whether it's driving or not. I'll check Vcc indeed. The thing is that there are many 245 …

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Re: Keyboard crashes on old 386 motherboard

Posted on 2022-02-17, 10:24

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by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Thanks Deunan I am passionate about electronics and I have been learning "as I go" for many years! I am mostly a "tinkerer" but I love learning new things so let me thank you for the time you spent in teaching me something new, I really appreciate that! It's a very interesting concept. I can indeed …

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Re: Keyboard crashes on old 386 motherboard

Posted on 2022-02-16, 23:22

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by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

gotcha. I'll test. Tonight I focussed on the bus around the KBC. The KBC is connected to the bus via a 74als245an which is a bus interface basically. I scoped the signal and noticed that this motherboard's ISA data lines are... pretty bad (yellow line, the purple line is the other side of the chip …

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Re: Keyboard crashes on old 386 motherboard

Posted on 2022-02-16, 15:35

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by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Thanks Deunan, All good points. Yes, that's a DX40 - makes sense to try 33Mhz. I shall let you know. The battery indeed corroded a lot, three traces were broken. I first bodged some wires at the back, then installed some thin wires. Since the issue was always there I got Necroware's (youtuber) …

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Re: Keyboard crashes on old 386 motherboard

Posted on 2022-02-16, 10:17

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by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

it's so weird that this issue only happens with Doom I found Doom to be extremly good at detecting bad cache chips or too aggresive timings set in BIOS. Keep in mind the keyboard only really works when connected to a PC, for example LEDs that light up when any of *Lock keys are pressed are …

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Re: Keyboard crashes on old 386 motherboard

Posted on 2022-02-15, 20:06

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by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

ahahah Sorry - so used to GB that I didn't realise what I typed! 🤣 I'll give that a go, thanks! Any chance you can point me to the right direction on "how to compile" slackware? I am a bit familiar with Linux but not enough... Any demanding games you can think of?

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Re: Keyboard crashes on old 386 motherboard

Posted on 2022-02-15, 16:11

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by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I still haven't fixed this motherboard - but I took a step back and decided I want to test it further as it's so weird that this issue only happens with Doom. I tried loading Duke3D but it doesn't work on a 386 apparently? Can someone recommend some demanding software which can run on a 386 with 8GB …

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Re: Keyboard crashes on old 386 motherboard

Posted on 2021-11-08, 10:14

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by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Question for the board: I've noticed that the data line of the KBC chip look very different on the affected MB than another one. On a working motherboard they look like usual: a mess of pulses. On the affected MB, there seem to be much less activity which slightly changes when using the keyboard. …

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Re: Keyboard crashes on old 386 motherboard

Posted on 2021-11-05, 15:02

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by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

little update XTAL 2 is grounded - hence no signal. Not sure whether it's not supposed to be grounded but it is and could not find a shorted component so far. I then did a little patchwork, lifted some of the VIA legs, connected XTAL1 to GND and XTAL2 to clock. It was not very good so the …

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Re: Keyboard crashes on old 386 motherboard

Posted on 2021-10-28, 17:33

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by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I didn't think of searching for the VT82C42, I was looking for the 8042! The datasheet is very clear and explains a lot. Yes, either case I should have the clock on XT2 so I'll investigate on that. Thanks a lot, I'll follow up with my findings!

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Re: Keyboard crashes on old 386 motherboard

Posted on 2021-10-27, 20:17

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by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I shall capture some screenshots and update here. In the meantime, would you be able to share the datasheet with me? For the life of me I cannot find it anymore... 😀 Thanks!

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Re: Keyboard crashes on old 386 motherboard

Posted on 2021-10-26, 19:07

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by tony359

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I've received the VT82C42. Unfortunately it works on other motherboards but not on this one. I then realised I did not do a more simple test: I put the suspected faulty KBC on another motherboard and everything works fine. No issues. So the chip is good. I then started scoping the chip on the …

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Re: Trident TVGA8900D - corrupted video output

Posted on 2021-10-19, 09:34

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by tony359

in Marvin \ Video

in Marvin \ Video

Umm, you wrote that it worked for a moment... I cannot find that - if I did, I did not mean that. It used to work, then it started showing those inversed text. Then, all of a sudden, it was fine again. I have been unplugging and re-plugging that board many times as you may imagine so I doubt it was …

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