Re: IBM PS/VALUEPOINT SX-33

Posted on 2025-05-12, 10:39

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

As noted before the board looks very good - the RAM sticks are ok - What is wrong here..??? It's an IBM, that's what. Most PC are clones and these don't care about the SIMM configuration jumpers/resistors, but this IBM just might. Make a close-up photo of your stick config please. Also on 486 …

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Re: 286 PC - using a 16 bit video card in 8 bit slot - which cards work ?

Posted on 2025-05-12, 10:30

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Was about to suggest it's an XT but you beat me to it. I spy 8088 CPU and 8255 chip that's XT specific. So for system that slow the 8800 might be a better fit, if only because it makes little sense to put such card in any other system. But then again it can emulate Hercules I think? So it would be …

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Re: 286 keyboard inductor gone bad

Posted on 2025-05-12, 10:21

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Just put something in there that's below 10uH and it should work. A wire jumper will do but I guess these original chokes died becuase of a short on the keyboard connector. So in essence these also work as fuses of sorts, preventing damage to chips and copper traces on the mobo. With wires this will …

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Re: 286 PC - using a 16 bit video card in 8 bit slot - which cards work ?

Posted on 2025-05-12, 10:10

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Why does it have to be 8-bit slot? It will greatly limit the performance of the card, and this is already a not so fast 286. 8900C is the best card for 286 I think, and not difficult to get. 8800 is slow but might be used if you prefer to keep other cards for better/faster systems. Note that 9000 …

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Re: P&Q M303 , 386SX, stuck on reset

Posted on 2025-05-11, 15:49

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Since you have a scope, check few more things. On ISA slot test B20 (CLK) and B30 (OSC) pins. I would expect the 14.31818MHz B30 to be present at all times, even with chipset in reset state. But the B20 (~8MHz) might be missing, that's why it doesn't show on POST card. That clock is usuall derived …

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Re: ADVICE SEARCHING ON CHOICE OF EEPROM PROGRAMMER

Posted on 2025-05-10, 22:48

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Windows these days is not that easy to infect if you have the default firewall and virus protection enabled. There might be some 0-day exploits but these are very rarely network-only. It almost always requires some program to be downloaded and run. So if you stick to the official T48 software I …

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Re: P&Q M303 , 386SX, stuck on reset

Posted on 2025-05-10, 22:32

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Hm. So you checked both clock sources with a scope? The 66MHz one is simple, it's a complete oscillator so when it gets 5V power it should produce output on it's own. But the 14.31818MHz needs a phase inverting amplifier and I guess the 74LS04 is used for that. So first make sure this clock is …

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Re: P&Q M303 , 386SX, stuck on reset

Posted on 2025-05-09, 23:00

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Well, first find out what that chip under RTC is excatly. Then find the datasheet. For example for 4069 type inverter the pin 1 is input to a gate, and pin 2 is the output of the same gate. So pin 2 should always have the opposite logic state to pin 1. The 4069 is a very commonly used as low power …

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Re: ADVICE SEARCHING ON CHOICE OF EEPROM PROGRAMMER

Posted on 2025-05-09, 22:48

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I'm going to assume the image file you mean is for the EPROM? The short answer is no, it can't infect it, but it could damage it. Longer answer is a very targeted attack like this is possible. But the attacker would have to know a lot of things, like what the EPROM is for, therefore what is the …

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Re: P&Q M303 , 386SX, stuck on reset

Posted on 2025-05-09, 17:05

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

PWR_GOOD signal not working properly perhaps? Even though there doesn't seem to be any significant battery damage. See that thin trace from power connector to nearby chip on the bottom of the PCB? That's the signal in question. Seems like there is another chip under the RTC, most likely a 4069, …

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Re: ADVICE SEARCHING ON CHOICE OF EEPROM PROGRAMMER

Posted on 2025-05-09, 13:47

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

1) No. I mean there are some 3rd party open source projects that works with TL866 but last time I checked these were very limited in what it can do. What people usually do is run the Windows software through Wine, seems to work well. There are some blogs and pages that describe what needs to be done …

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Re: ADVICE SEARCHING ON CHOICE OF EEPROM PROGRAMMER

Posted on 2025-05-09, 10:21

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

TL866 is now considered EOL. If you have one, great, keep using it - don't expect any software updates though. But if you are looking to buy a new programmer then XGecu T48 is the way to go.

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Re: NEC multisync XV17 JC-1734VMA repair suggestions

Posted on 2025-05-08, 10:53

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

You won't get HV without HOT on most monitors, it's generated by the same pulses that drive the horizontal deflection. In fact quite a few monitors have a simplified PSU that delivers B+ and one, maybe two low voltage rails for the logic circuits, and the rest (like CRT bias voltages, aux. …

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Re: Cyrix DX2-80 slower than DX2-66?

Posted on 2025-05-05, 13:57

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I admit I have not verified these claims vs Quake source, I based my comment on "common knowledge" from YT videos and the like. So if that's just another Internet rumour I stand corrected. That being said I gave the sources a look and while the Q_memcpy is only optimized for 32-bit bus cycles if the …

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Re: CRT "ticking"

Posted on 2025-05-05, 12:48

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

That's a HV discharge. If it's inside the CRT there is nothing you can do. It has some air and it'll either keep doing it or get worse. If it's the flyback transformer developing internal short it's also bad, and nothing you can do. It will fail eventually. But it could also be dust buildup and/or …

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Re: NEC multisync XV17 JC-1734VMA repair suggestions

Posted on 2025-05-03, 23:28

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

So it would seem the PSU trips shortly after B+ goes up. It can't be a dead short if you see the meter show something but it's soon gone. That being said check the HOT first, could be the PSU doesn't detect the short and what you see is just a couple of volts dropped on the resistance of the copper …

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Re: Floppy controller not working in DOS/WinXP but works during boot

Posted on 2025-05-03, 23:12

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Real HDD or CF card? I've seen some CF cards not play nice with floppy controllers. Could also be another card that, for some reason, uses that I/O space. I would suggest to test with bare bones, VGA, HDC+FDC and that's it. No drivers either, including mouse, just to rule out software issues in DOS …

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Re: Cyrix DX2-80 slower than DX2-66?

Posted on 2025-05-01, 22:56

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

A rumour, that is not written in this analysis is Cyrix has slower internal cache speeds, equal to bus speed as opposed to Intel. I've dug up some CACHECHK results I did for Cyrix and Intel, both at 66 (33x2) MHz. So here's what it looks like: Cyrix at 66MHz: 1 2 4 8 16 32 64 128 256 512 1024 2048 …

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Re: Cyrix DX2-80 slower than DX2-66?

Posted on 2025-05-01, 09:04

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

For Quake case, I dont think that fpu speed difference describes everything, there is huge difference! AMD DX2-80 (copy of intel) runs at 10.2 fps but CyrixDX2-80 gives 5.7 fps. This is ridiculous on same board with same memory settings. It depends on what instructions are used, and how heavily. In …

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Re: Cyrix DX2-80 slower than DX2-66?

Posted on 2025-04-29, 11:19

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

No, I think it's the other way around. FPU on Intel DX2 is considerably faster than on Cyrix. Reason being the Cyrix is not (unlike AMD) a copy but they did their own implementation, based on earlier work with x87 chips. What should be faster on Cyrix is integer multiplication (considerably so) and …

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