Re: Help needed reviving AST 486 motherboards (SOLVED) + benchmark results

Posted on Today, 00:04

by

by SSTV2

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

No, the onboard video does not need to be configured via the EISA utility (there is basically nothing to configure), however, refresh rates can be changed through the BIOS. By default, the refresh rates are as follows: 640x480 - 60Hz, 800x600 - 56Hz and 1024x768 - 87Hz-interlaced. If the problem is …

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Re: Looking for Targa Win Tseng Labs ET4000 ROMs

Posted on 2025-05-31, 13:49

by

by SSTV2

in Marvin \ Video

in Marvin \ Video

Glad it worked out, you could also try BIOS from other vendors that used this chip, I know that ROM pack for 86Box/PCem has newer BIOS versions for ET4000 than the one I provided here, which might support more VESA modes.

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Re: Looking for Targa Win Tseng Labs ET4000 ROMs

Posted on 2025-05-30, 21:06

by

by SSTV2

in Marvin \ Video

in Marvin \ Video

Here you go, I noticed something interesting about the BIOS - both HIGH and LOW images are identical, I've also included XROM (sync BIOS) for completeness, all chips are mask ROMs of 27C256 EPROMs. Filename label+RAMDAC.jpg File size 554.71 KiB Views 185 views File license Public domain Filename …

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Re: Looking for Targa Win Tseng Labs ET4000 ROMs

Posted on 2025-05-29, 20:50

by

by SSTV2

in Marvin \ Video

in Marvin \ Video

Hi, I have this exact video card and I'll try to dump its BIOS image tomorrow via the EPROM programmer as soon as I'm free, just let me know if you are still looking for it.

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Re: Need help - Tekram P6PRO-A5 Troubleshooting

Posted on 2025-04-29, 19:36

by

by SSTV2

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Strange readings, the motherboard was off, right?

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Re: Gateway 2000 bad I/O board?

Posted on 2025-04-29, 19:22

by

by SSTV2

in Marvin \ Video

in Marvin \ Video

I wouldn't call myself a CRT specialist, but this chip must be the RGB video preamplifier, probably an LM1203 or some similar RGB preamp. The actual RGB amplifier stage is made using high power BJTs and should be located on the CRT neck board. If red color amplifier is OK and the preamp chip is …

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Re: Need help - Tekram P6PRO-A5 Troubleshooting

Posted on 2025-04-26, 13:25

by

by SSTV2

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It seems that all the main signals are connected to the northbridge and are in working order, so now we are left with the control signals and perhaps clock. I summarised the readings of a DIMM slot for this M/B and measured the voltage drop across control and clock pins (positive DMM probe on ground …

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Re: Need help - Tekram P6PRO-A5 Troubleshooting

Posted on 2025-04-25, 18:30

by

by SSTV2

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I see 2 possible problems: Pin 28 "DQMB1" must be connected as in the rest of the slots and pin 79 of "CK2", there should be no resistance between the pins, if you get a resistive reading, something is shunting that clock signal. Take a good look at those resistor networks near the clock generator …

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Re: Need help - Tekram P6PRO-A5 Troubleshooting

Posted on 2025-04-24, 22:33

by

by SSTV2

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay so testing each pin of the memory slots from the top gives me near identical readings for all slots. I cannot find anything suspicious there. It's the same pins on different sockets that should be checked for continuity, not any other way, e.g. pin 2 of slot1 and pin 2 of slot3 (Data 0) and so …

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Re: NEC multisync XV17 JC-1734VMA repair suggestions

Posted on 2025-04-24, 13:17

by

by SSTV2

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

hi all! i'm about at my wit's end here... long story short, i have ended up with a very cheap NEC multisync XV17 CRT from 1995 that has given me a whole load of trouble as i've tried to get it up and running again. when i first got the monitor, it did indeed work as advertised... in that it would …

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Re: Need help - Tekram P6PRO-A5 Troubleshooting

Posted on 2025-04-24, 13:06

by

by SSTV2

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Since the slots are wired in parallel, would it be a fair assumption that the connections are good under the north bridge because the other two slots are working? With the board not powered, I did measure the contacts of the slots from the top the other day and compared the results to the other …

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Re: Need help - Tekram P6PRO-A5 Troubleshooting

Posted on 2025-04-24, 03:16

by

by SSTV2

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

This motherboard was the one I had in the early 2000s with a 700MHz Pentium III, still have it, but avoid using for a build. SDRAM slots are basically wired in parallel, except for some control signals like /WE, /CSx, /CAS, CKx (clock) etc. Compare the data (64) and address (14) bus pins of the …

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Re: Replacing Matsushita drive spindle motor

Posted on 2025-04-19, 03:29

by

by SSTV2

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Such micro DC brushed motors could be salvaged from other CD-ROM drives (used in tray mechanisms) or portable CD players "Walkmans", PSX laser assemblies also used such motors for spindles, though always consult datasheets to get a closest match.

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Re: Intel 486DX4-100 @ 120MHz ?

Posted on 2025-04-16, 00:01

by

by SSTV2

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Most DX4-100s from intel or AMD do not run reliably at stock voltage when overclocked to 120MHz, you need to raise the voltage to 3.6V for that, if it still does not run reliably at 3.6V, you then may need to customize the voltage regulator for 3.7-3.8V output, anything above 3.8V is harmful for the …

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

Posted on 2025-02-26, 15:06

by

by SSTV2

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Interesting observation - I tried to align heads using IMD alignment test and the drive passed it with a formatted HD diskette, but in reality, the FDD was still unable to read formatted DD or HD diskettes, so I had to align heads the old-fashioned "trial and error" way. This is an inconsistent …

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

Posted on 2025-02-25, 15:56

by

by SSTV2

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Cleaned the heads of a 5.25" FDD (TEAC FD-55GFR), which were contaminated with magnetic film from some old rotting diskettes. It caked up so hard that even a cleaning diskette couldn't deal with the dirt, so I had to completely disassemble heads and scrape that stuff off. Interesting observation - I …

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Re: [Help] Did I lose my K6-2+? :(

Posted on 2025-02-18, 14:17

by

by SSTV2

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Partially working CPU is a sign of damage from overheating or prolonged overvoltage. I have two such CPUs, one was damaged by overvoltage, the other by a poorly mounted heatsink, which made only a partial contact with the CPU die (heatsink tilt). Both CPUs are functional enough for an early …

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Re: IBM PS/1 upgrade project

Posted on 2025-02-10, 18:18

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by SSTV2

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I did not unfortunately. I got the ZIP40's on E-bay for next to nothing, so it was a no brainer to get High Colour. Dang, those SOJ40 ICs are very common, maybe I'll just make a SOJ40->4xZIP20 interposer module when I get bored enough one day. You should try tweaking RAM timings instead, …

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Re: IBM PS/1 upgrade project

Posted on 2025-02-10, 00:35

by

by SSTV2

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

If you can't get past the HDD detection, you can try disabling HDD or IDE ports via BIOS setup and booting from a startup floppy with Speedsys on it. Clean boot might also help, press F8 while booting and select "step-by-step confirmation". By the way, do you have a benchmark of the video card …

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Re: IBM PS/1 upgrade project

Posted on 2025-02-09, 02:12

by

by SSTV2

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Awesome project, it's always fun to push old systems to their limits. A few weeks ago I was tinkering with a very similar system, specifically an HP Vectra 486/25VL. This system also came with an integrated 486SX-25, 4MB RAM, 512KB CL5426 and no option to add L2 cache. Despite these shortcomings, …

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