Re: „Below the root” hangs on IBM Portable 5155

Posted on 2020-10-16, 11:22

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by kdr

in Marvin \ Software

in Marvin \ Software

Well, I couldn't resist, so I've unpacked the 5155 and found a copy of the game. It's the one with a tiny LOADER.COM, not the booter. (Which I wasn't able to find.) The results: running PC DOS 2.10, the LOADER.COM did nothing and just returned me to the DOS prompt. Running MS-DOS 3.30, the LOADER. …

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Re: „Below the root” hangs on IBM Portable 5155

Posted on 2020-10-16, 10:12

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by kdr

in Marvin \ Software

in Marvin \ Software

On another forum, one of the users confirmed the problem with the game and 5155. Interestingly, the game works on 5160 (the same mainboard) 'Probably a bug in the "determine what this machine is" code, which reads the Model ID byte in ROM.' It makes sense, but afaik id. byte is in FFFFE FE is there …

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Re: 486 PSU questions

Posted on 2020-10-15, 22:49

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Unlikely. There's no way that a 486 mobo on its own is going to overload an AT PSU that can supply 15A on the +5V rail! The very first thing to check is to see if any of the power rails on the mobo are shorted (typically due to a blown tanalum capacitor). If there's a short the PSU won't start up. …

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Re: ATX PSU with -5v

Posted on 2020-10-15, 22:42

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by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Some of the ATX to AT adapters include a small linear regulator to generate the -5v rail, and that's an option to consider -- the current draw on -5v is minimal, so there's no need for anything fancy. (I believe they use something basic like a 7805 hooked up to the -12v rail?) Otherwise go search …

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Re: „Below the root” hangs on IBM Portable 5155

Posted on 2020-10-15, 22:35

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by kdr

in Marvin \ Software

in Marvin \ Software

My first thought was that the game might be compiled to use 80286 instructions, but then I looked up the game and saw it was from 1984. :) Have you been able to run your copy of the game on any other 8088 machines? I've had a couple of programs hang or otherwise exhibit weird behaviour and the root …

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Re: 6€ MCE2VGA replacement - CGA/EGA/HGC capture with logic analyzer

Posted on 2020-10-15, 01:44

by

by kdr

in Marvin \ Video

in Marvin \ Video

I've recently ordered a couple of cheap Cypress FX2LP eval boards from China (so they'll take ages to arrive) because I need a 16ch logic analyzer to debug an old Turbo XT motherboard with glitchy DMA. I'm also hoping to be able to play with Predator99's awesome video capture code! In preparation I …

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Re: Thoughts on rebuilding an XT PSU versus swapping in newer AT PSU board into the old XT PSU case

Posted on 2020-10-14, 00:33

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I have one of those ~19V DC-DC ATX power supplies (rated for ~150W) and the board itself is quite small. So I might gut the PSU (saving the board for future repairs!) and install a 19V power brick [maybe salvaged from a beefy gaming style laptop?] inside, along with the DC-DC supply and an ATX->AT …

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Re: Bought these (retro) hardware today

Posted on 2020-10-13, 02:21

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by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Today's $50 e-waste haul: IIMG_20201013_150804.jpg Some PS/2--AT keyboard adapters (both kinds), a MIDI cable, an AUI to 10BaseT media converter, some generic 8-bit network cards... But the star of today's show is the VLB Super I/O, the first time I've ever found a VLB card "in the wild": IIMG_ …

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Re: Thoughts on rebuilding an XT PSU versus swapping in newer AT PSU board into the old XT PSU case

Posted on 2020-10-13, 01:59

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I have a dead PSU in my IBM 5160 XT, and am also wondering about repair vs replace. I haven't tried to diagnose the PSU failure yet, it's a bit beyond my abilities still. In favour of (attempting to) repair: keep the 5160 as close to original as possible!

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Re: Is an Arduino IPU possible for Vintage PCs?

Posted on 2020-10-12, 22:14

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by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Some general comments ... Encryption on older DOS machines: Everybody points out the obvious - that mTCP doesn't have an SSH client. I've looked into what it would take and there are two significant problems: Processing speed. For modern ciphers at reasonable bit lengths you don't have enough CPU …

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Re: Is an Arduino IPU possible for Vintage PCs?

Posted on 2020-10-12, 09:28

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Why not do it yourself ? You already know where to start! Now Start Off! I really would see your efforts :-) I've been working my way up to it! Since I'm being pedantic and insisting on using only the tools that are era-appropriate, there has been a somewhat steep learning curve involved.I've …

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Re: motherboard repair

Posted on 2020-10-12, 01:11

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I recently rescued a 486 mobo that had some bad Varta leakage. Luckily the corrosive goop hadn't destroyed any important traces, because the battery was mounted in an area of the board that didn't really have anything nearby. It's important to neutralize the gunk (I used vinegar) and then rinse the …

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Re: Bought these (retro) hardware today

Posted on 2020-10-12, 00:59

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Today I scored a nice mid-90s HDD from the local recycling centre: IIMG_20201012_134506_1.jpg It spun right up! It's a lovely 1GB 3600rpm Conner drive. Surface scanning is still in progress, but it looks to be in perfect condition. Still has a bunch of files on it from a Win95 install, but nothing …

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Re: Is an Arduino IPU possible for Vintage PCs?

Posted on 2020-10-11, 21:47

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I think that implementing a modern TLS cipher suite on an 8088 would be an excellent low-level asm coding challenge! I suspect that the 8087 could help accelerate the public key crypto, too: in addition to floating point, the 8087 can do 64-bit integer arithmetic. Also, implementing POLY1305- …

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

Posted on 2020-10-11, 04:47

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I never run Memtest on cd or usb thumb drive on anything older than soc775... too many quirks. Some versions of Memtest are very hardware specific (ver 4.0 will run on 486 but v4.3 will not). You should use a 1.4Mb 3.5" floppy disk and use the appropriate version for the older hardware you are …

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Re: Is an Arduino IPU possible for Vintage PCs?

Posted on 2020-10-11, 04:07

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I am also interested in using the modern Internet from vintage computers. These days, "Internet" is synonymous with "HTTPS connections serving multiple megabytes of Javascript code", and even my modern i5 laptop with 8GB of RAM struggles to render some of the bloated pages out in the wild. So surely …

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

Posted on 2020-10-11, 03:51

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Picked up two of these nice ASUS Socket 7 boards this weekend, both with AMD K6-200Mhz CPUs, one with 64MB (pictured) and the other with 128MB: IIMG_20201011_163831_1.jpg This board has two power connectors, one AT and one ATX! So I won't have to consume a valuable AT PSU if I build a system with …

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Re: Sigma Designs EGA cards - a deep dive

Posted on 2020-10-10, 22:58

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by kdr

in Marvin \ Video

in Marvin \ Video

I guess, I just solved a part that mystery: The card just doesn't support 200 lines modes. CRF9 is set to 3 in all 200-line modes, and set to 0 in all higher-resolution mode (including the text modes with a 8x14 character cell). This most likely means the card double-scans 200-line modes as 400- …

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Re: Sigma Designs EGA cards - a deep dive

Posted on 2020-10-10, 11:31

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by kdr

in Marvin \ Video

in Marvin \ Video

I am intruiged by the idea of adjusting a fixed frequency monitor such that it can sync at a different frequency. It just so happens that I have a half-working fixed frequency MDA monitor -- it shows intense text just fine, but doesn't show normal text -- which could be 'sacrificed' in the name of …

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Re: Sigma Designs EGA cards - a deep dive

Posted on 2020-10-10, 01:45

by

by kdr

in Marvin \ Video

in Marvin \ Video

In the IBM design, there is another register 3c5 called clocking mode register. There is a bit controlling the dot clock. So it's generated in the sequencer in the IBM design, and they should support this, if they were trying to be compatible. Ah yes, forgot about that one! Yes, the sequencer ( …

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