Re: MFM 5.25 floppy with 5ali61

Posted on 2021-05-24, 19:01

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Current limited PSU..? I don't own one. But I guess I could measure the current with a multimeter in series? Can also maybe test it outdoors and outside the computer case. :-) Well you can, at least you'll know how much power it actually needs, but the point was to limit the current in case of a …

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Re: MFM 5.25 floppy with 5ali61

Posted on 2021-05-24, 18:49

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Ah, so are both the 220Ω and 330Ω part of the termination, and only found on the last drive in a chain? That should be the case, yes. This is analog signal handling territory, I know a bit about that but again I'm no expert. In general you want to match the cable impendande but that's not fully …

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Re: MFM 5.25 floppy with 5ali61

Posted on 2021-05-24, 15:08

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

One thing I definitely don't understand are the diagrams on sheet 15/19 (page 8 in your scan). Don't know why there's both a 220 ohm pull up and a 330 ohm pull down. This may be some detail of the 74LS that I'm missing. Also, there mention of termination resistors on sheet 7/19, which I'm not sure …

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Re: Strange 386 Issue

Posted on 2021-05-24, 13:19

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Soldered RAM is annoying, and not being able to run any programs even more so. Might not be any other way but to desolder and put sockets in (if there is enough space). Sometimes swapping the chips around causes the system to act differently, then you know it's the RAM. Though it might still be …

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Re: MFM 5.25 floppy with 5ali61

Posted on 2021-05-24, 13:13

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I am a little confused about the section about the power on page 11/19. I have a 4 pin Molex connector on my model, but I also have the 10 pin molex connectors. Is 4 pin molex is enough? Maybe the other connectors are there for compatibility reasons? It looks like your drive needs DC only and it's …

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Re: Strange 386 Issue

Posted on 2021-05-24, 10:36

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Could be faulty RAM - can you swap it for something else to make sure?

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Re: MFM 5.25 floppy with 5ali61

Posted on 2021-05-24, 10:30

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Yes typo. 34 pin! "Standard" and I don't have one yet. I'm a little confused about if I need to modify the connector (which should be quite easy to do) because there are a couple of pins that are not according to to shugard standard, the ones without stars next to them in the manual. I actually …

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Re: Hardware mod for L1 cache support on Cyrix 486DLC/SXL CPUs

Posted on 2021-05-23, 12:23

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I guess, I'll have to find another Mainboard in order to get a 40MHz System Well, that sucks, but at least you know that now rather than chasing phantom problems later. I've run some tests to actually see how much BARB affect performance - because it will flush cache on all DMA requests, be it …

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Re: Help needed with 3Com 3C509B EtherLink III

Posted on 2021-05-21, 14:46

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Linux to the rescue! I have another busted 3Com card, a PCI 905B series (this one mysteriously stopped working years ago), so I figured I might try to tackle that problem too. I peeked into Linux driver sources and found some EEPROM checksum calculation, decided to try that method on my images. I'm …

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Re: Stuck debugging and repairing Commodore PC-10 III

Posted on 2021-05-21, 14:15

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Chances are the original BIOS memory test is not as robust and misses some clues, then proceeds to use some RAM for stack or something. And then it obviously fails. While it's going to be a lot of work, and there's always the risk of some trace/via damage that has to be repaired as well, I think …

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Re: Hardware mod for L1 cache support on Cyrix 486DLC/SXL CPUs

Posted on 2021-05-21, 08:42

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

There's an old DOS program called Gold Memory, it's a pretty good RAM tester. Try that one too to see if you have any memory issues (note, cache issues will cause random memory failures but if you get a pretty repeatable addresses reported it's most likely RAM sticks).

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Re: Stuck debugging and repairing Commodore PC-10 III

Posted on 2021-05-21, 08:39

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I didn't dig for very long but I can't find datasheets for these - other than LM33256G being 256kx1 and M41464 being 256kx4. Which also matches the number of chips you have - this system has 512k RAM total, correct? Reason I asked is the older tech DRAMs needed +12V and sometimes also -5V in …

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Re: Tandy 4825 sx Wont Post - Suspect Bios from codes. Anyway to make a new one?

Posted on 2021-05-21, 00:07

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Do you have a POST card? I could hack you a simple test image that outputs some codes, maybe even do a self-test of the entire BIOS area so you would know if that's being read correct or not.

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Re: Help needed with 3Com 3C509B EtherLink III

Posted on 2021-05-21, 00:03

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It seems I got the card error-free by changing it's config to full duplex. During saving 3Com configuration program clears the last 16 bytes of the EEPROM image, and modifies a few more, but now all checksums are finally correct - and the card is still a 509B model with my MAC and manufacturing date …

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Re: Stuck debugging and repairing Commodore PC-10 III

Posted on 2021-05-20, 23:39

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Out of curiosity, what type of memory chips does this machine use? And which voltage rail got the short on it?

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Re: Help needed with 3Com 3C509B EtherLink III

Posted on 2021-05-20, 21:30

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The good news: The idea was good, and my program works, I was able to write the modified image back to EEPROM. The card is now recognized as 3C905B-Combo and all the HW tests pass, including FIFO. The bad news: It seems in the extended data chunk there is yet another checksum because the EEPROM …

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Re: Help needed with 3Com 3C509B EtherLink III

Posted on 2021-05-20, 18:47

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Oh it sure does, the second card is a -C(OMBO) identical to mine. This dump alone should get me what I need, but with the screenshots I can now try to figure out where exactly my data is glitched. Many thanks!

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Help needed with 3Com 3C509B EtherLink III

Posted on 2021-05-20, 17:28

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I got that card recently and to test it I put it into P200MMX with Win98SE. Windows detected it, copied drivers, but complained on every boot that the HW isn't working properly. I've decided to try and change the card settings (port and IRQ) on that machine, even though the buggy 3C5X9CFG.EXE …

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Re: Hardware mod for L1 cache support on Cyrix 486DLC/SXL CPUs

Posted on 2021-05-20, 16:48

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It's weird that your mobo doesn't boot in high speed - could be mobo cache issues. But if the button works lets worry about that one later. Don't use fast A20 gate if you have issues, I've seen mobos (even have one) that don't actually implement it even though there is an option to enable it. Not a …

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Re: Bought these (retro) hardware today

Posted on 2021-05-20, 16:38

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Got myself an interesting CRT today, which seems to be EGA monitor. It's Thomson 4460D. It requires some adjustment; we'll see if it works at all. I kinda like the design. EGA CRTs seem to be rare - It's the first one I have seen for sale for a long time. I saw that one on sale too but figured I …

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