Re: Getting power to a fan on an old computer... is the sound board an option?

Posted on 2022-10-10, 21:13

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I often re-wire the Molex connectors of 12V fans to run them off the 5V rail instead, this makes them run fairly slow and very quiet. If you have a tiny screwdriver and some patience it's possible to slide the pins out of the plastic housing, so you don't even need to crimp or solder anything! (Edit …

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Re: What are some great games for 8088 computers?

Posted on 2022-09-30, 01:09

by

by kdr

in DOS

in DOS

Playing Secret of Monkey Island on an 8088 is torture, but there it is on the front of the box. Barely playable was the norm back then, if you think Monkey Island was slow on an 8088 Secret of Monkey Island is quite playable (albeit a tad sluggish) if you've got a Turbo XT. I sure wouldn't want to …

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Re: What ISA cards for an IBM 5150?

Posted on 2022-09-29, 04:49

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

At this point, I'll be happy if the thing turns on after I recap it. It's actually very rewarding to play around with an IBM PC and its basic CGA graphics. The best part about CGA is that the games are perfectly playable using the composite video output because all you need is a regular television …

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Re: Is it possible to get CGA NTSC Artifact Colors when running an IBM PC in Europe?

Posted on 2022-09-29, 04:20

by

by kdr

in Marvin \ Video

in Marvin \ Video

IBM PCs with CGA graphics adapters were able to produce "artifact colors" when running in the NTSC region Even in PAL regions the IBM PC with CGA generates video with NTSC timings (262 lines per frame at 60 frames per second) on both the RGBI (digital) and the composite outputs. On the composite …

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Re: 15kHz why does it matter,what is the fuss about?

Posted on 2022-09-23, 07:48

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

On the PC the big deal is that CGA/EGA games were designed with 15.7khz RGBI monitors in mind: you get 16 fixed colours and the monitor displays 200 scanlines with fairly large black areas between each line. You can play these games on a VGA system, but they are displayed in a double-scanned scheme …

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Re: What ISA cards for an IBM 5150?

Posted on 2022-09-23, 07:41

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I'm open to suggestions for the VGA and Audio cards, and would prefer "new" cards to vintage ones to avoid capacitor troubles. What might be a good option for the fifth slot? (My 5150 is configured with 100% IBM expansion cards as a proper "period correct" system, but that's because I have other …

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Re: Bought these (retro) hardware today

Posted on 2022-09-23, 03:23

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Wow thats a really cool find I have never seen this card! I have also been using COPY II PC and it was able to copy all my copy protected disks even without that card. Please let us know if/how it works! Yeah this is easily one of my "top 5" finds from trawling the local markets etc. When I first …

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Re: Debug an 8086 that won't power up

Posted on 2022-09-22, 09:42

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

There are clear signs of bus contention visible on the oscilloscope waveforms. Not necessarily. While CMOS drives 5V for a logic '1', the 74xx series TTL has weak logic '1' levels and can only get the output up to 3.6V-3.8V or so. I can see a lot of 74LS logic on that XT clone's motherboard and the …

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Re: Bought these (retro) hardware today

Posted on 2022-09-22, 03:24

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Went to one of the local recycling centres (which doesn't usually have any retro gear at all) and to my surprise found a box of assorted ISA/PCI/AGP cards for $1 each! Grabbed the best five and left the remainder for the weekend warriors to rummage through.... can't be too greedy heh heh IMG_ …

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Re: Debug an 8086 that won't power up

Posted on 2022-09-21, 21:22

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

What else can I try? If you ground the IOCHRDY signal (pin A10) on the ISA bus and then power on the machine, the CPU will halt immediately before fetching the first instruction from ROM. This should leave all the data and address lines static and you can then check the various chip selects and bus …

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Re: Did VGA (EGA?) standard lose support for CGA Mode 5h color palette with light red color?

Posted on 2022-09-21, 21:14

by

by kdr

in Marvin \ Video

in Marvin \ Video

I wonder if the light red color was more like a bug/unintended artifact, that was a side result of disabling color bursting, rather than an intended effect? It was intentionally designed that way by IBM but left undocumented. (Just like the 16-color 160x100 "graphics" mode.) My theory is that the …

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Re: IBM VGA BIOS initialization

Posted on 2022-09-12, 20:50

by

by kdr

in PC Emulation

in PC Emulation

I seem to recall that "Vertical Retrace" (both the status bit and the optional interrupt) is triggered by the scanline counter reaching Vertical Displayed End. The intention must have been to inform the program "okay now you can write to video memory without worrying about screen tearing". …

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Re: What is a genuine PC?

Posted on 2022-09-07, 20:32

by

by kdr

in Milliways

in Milliways

I did not know this! The source I recall reading on the matter (wish I remember what it was) led me to believe that the creation of a clone army was unintentional on IBMs part and more or less resulted from them "rushing it" - ie. the use of off-the-shelf parts was more of a timesaver than a …

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Re: What is a genuine PC?

Posted on 2022-09-07, 08:12

by

by kdr

in Milliways

in Milliways

It's the use of off-the-shelf parts that allowed the reverse-engineering and cloning of the early IBMs so easily, and effectively allowed all the clone-makers to piggy-back on IBM's brand and software selection. There wasn't any reverse engineering required, IBM literally published the full …

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

Posted on 2022-08-29, 06:57

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Today I am installing MS-DOS 5.0(a) on the 486DX2/66, very pleased that I found a nice clean desktop style case to hold all the retro componentry. Filename IMG_20220829_183535.jpg File size 473.6 KiB Views 960 views File comment (nostalgia overload)

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Re: Help upgrading XT clone to NECv20

Posted on 2022-08-25, 03:09

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Thats ok, i only need it at about 4.77 mhz anyways, from what i can tell its a more powerful cpu even at the same frequency Don't set your hopes too high, the V20 is only marginally faster when running real-world code. Its main advantage is that it implements all of the extra instructions that the …

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

Posted on 2022-08-11, 10:27

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Spent the evening getting the new AREA 5150 demo running on my IBM PC. After all, it's not every day that there's new software released for the 8088! The demo is meant to be run from a hard drive but I keep my 5150 in its original state: just the dual 360K floppy drives. Managed to get it working in …

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Re: Converting a PC Booter Game to Cassette Tape

Posted on 2022-06-19, 22:37

by

by kdr

in Marvin \ Software

in Marvin \ Software

Personally, I think it's a shame that IBM engineers removed the port. That was soo unnecessary. Couldn't they at least leave some Cassette IN headers on the later motherboards? Just like for the internal PC Speaker (which was Cassette OUT )? For a long time I never understood the bizarro design of …

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Re: Converting a PC Booter Game to Cassette Tape

Posted on 2022-06-19, 07:23

by

by kdr

in Marvin \ Software

in Marvin \ Software

Wow, awesome, I have always been fascinated by the (almost useless) cassette port on my 5150. Guess I'd better go dig out the tape player and get it connected up...

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Re: 8-bit memory/RAM cards

Posted on 2022-06-03, 06:51

by

by kdr

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

640KB on ATs.. Yes and no. Yes, 640KB were the norm. But some of their CMOS Utilities allowed dividing 1MB into 512+512 and/or 640+384 (base memory+extended memory or shadow RAM). So it's theoretically possible to set it to 512KB, and use an UMB card to fill in 128KB into 512-640KB, and the rest …

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