Re: POST fails with defaults loaded

Posted on 2021-07-17, 20:32

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by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay yeah, grabbed two known PC100 128mb sticks and tried to make it fail POST and the problem went away. So either the BIOS is trying to make it run a memory frequency it can't support or something else is unhappy about the higher speed. Performance isn't a big issue here though so I'm happy.

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Re: POST fails with defaults loaded

Posted on 2021-07-17, 18:20

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by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Yes, made a mistake there. Looks like a PC100 stick got mixed into my PC133 bin. To clear things up I just tested it: 1 x 256mb PC133 SDRAM = One-time post, then memory error beep after reset 1 x 256mb PC133 SDRAM, configured in BIOS to run at PC100 = Reliable POST 1 x 256mb PC100 SDRAM = Reliable …

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Re: POST fails with defaults loaded

Posted on 2021-07-17, 18:06

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by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The sticks I have say that they are rated for PC133. I have not popped the heatsink off but it seems to imply it's a 1Ghz PIII with Tualatin's telltale top heat spreader. THOUGH now that you mention that I noticed the fail-safe forces PC100 mode and the system seems to run reliably at that. Its when …

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POST fails with defaults loaded

Posted on 2021-07-17, 17:43

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by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I'm building a disk imaging station and assembled a system around a PEAK 650 Socket 370 SBC board. The board does have a few tiny passives knocked off from rough handling (looks like a screwdriver was used to pry off the tabbed CMOS battery instead of snipping it off) but it still POSTS fine, to a …

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

Posted on 2021-07-11, 22:20

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by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Finished installing a remotely accessible DOS machine, dubbed the BoilerPC. Runs Carbon Copy Plus and hides behind the boilers in a 100 year old building. Spent the last month and a half just trying to find the appropriate furniture to match it with. https://hosting.photobucket.com/images/a166/ …

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

Posted on 2021-05-19, 04:33

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by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

No it's just down there where it can't be found. I rebuilt the power supply and made the case as secure as possible to prevent the dirty workspace and any animals that get onto the desk from bringing the system down. The modem uses a "secret" PBX extension so from anywhere inside the building and …

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

Posted on 2021-05-19, 03:14

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by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Completed the Boiler Room Build. https://hosting.photobucket.com/images/a166/ballsandy/IMG_8487.JPG 66mhz 486DX2 machine with VLB trident video, 8mb ram, floppy drives and a 256mb SSD with a Colorado Jumbo250 for tape backup (and yes it works!) Not an exceptional performer but a machine that is …

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Re: What retro hardware you killed today or in the past :(. Killing spree stories+serial killers are welcome.Rest in pie

Posted on 2021-05-08, 02:13

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by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Had a floptical drive for a Silicon Graphics Iris Indigo that wouldn't read floppies. To test if it was the special Teac-chipset SCSI to floppy bridge or not I haphazardly plugged it into another machine with SCSI but didn't observe pin 1. Fried it. I've never seen a SCSI device fry like that before …

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Re: 486 will not boot from floppy; will not read from floppy either

Posted on 2021-05-03, 13:42

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by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I just had a look and can't see this version of the board listed on UH19. The closest I could find (searching for 85C461 chipset, 486SV2) is the VL/ISA-486SV2 Rev 1.72: http://www.win3x.org/uh19/motherboard/show/821 but that has no photo to compare with. You took a good photo right at the top of …

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Re: 486 will not boot from floppy; will not read from floppy either

Posted on 2021-05-02, 22:58

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by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

maybe that particulare '151 is faulty after all. I really dislike desoldering stuff from mobos, because sometimes the old traces/vias get damaged and there's even more stuff to fix, but with no other tools and ideas I would try to desolder this '151, and the other one that has IRQ12 connected to it …

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Re: 486 will not boot from floppy; will not read from floppy either

Posted on 2021-05-02, 17:15

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by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Oh well. Let's dig deeper into this. See if /E input of the '151 (pin 7) is connected to chipset or tied to GND permanently. It is tied to ground. est inputs S0,S1,S2 (pins 11,10,9), you should see them toggling. All the time actually to properly scan all inputs, unless this chipset is "smart" and …

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Re: 486 will not boot from floppy; will not read from floppy either

Posted on 2021-05-02, 00:02

by

by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

DRQ0, 1, 2 and 3 all run to the same chip (U8) and not to the chipset directly. U8 is a SN74F151BN 8-Input Multiplexer : -DRQ0 to pin 15 -DRQ1 to pin 14 -DRQ2 to pin 13 -DRQ3 to pin 12 I pretty quickly had a Sound Blaster Pro 2 available so I threw that in and ran TEST-SBP. The digitized sound test …

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Re: 486 will not boot from floppy; will not read from floppy either

Posted on 2021-05-01, 21:40

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by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

That I can tell, A B and C never go low A connects to 183, B connects to 182 and C connects to 181. pins 4 and 6 remain high while 5 remains low. One thing also I have not checked yet is if DRQ2 is actually reaching the chipset. I've only probed from the ISA bus. That would go to pin 149 in one way …

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Re: 486 will not boot from floppy; will not read from floppy either

Posted on 2021-05-01, 19:33

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by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

U24 is a 74LS138N 3-line to 8-line decoder. Okay so if I'm reading that right, DRQ2 is the floppy controller sending a DMA request to the chipset ("Mr 85C461 can I plz use DMA channel #2?"). The chipset responds back with DACK2 ("Yes device, you can use DMA channel #2 until I say stop.") If I'm …

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Re: 486 will not boot from floppy; will not read from floppy either

Posted on 2021-05-01, 17:59

by

by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

So I double checked to see if the scope was fast enough to trigger and display activity on DACK2 using the test board and yes I can see it pull low on floppy boot (and I just discovered that the vertical adjustment on channel 1 has stopped working so I'm only able to watch one pin at a time using …

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Re: 486 will not boot from floppy; will not read from floppy either

Posted on 2021-05-01, 16:44

by

by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I'm sure this has already been covered, but on the controller card, does it have IDE ports with anything plugged in to them, and do they work correctly (this should test whether anything can get data across the bus from that particular card)? Can you post a photo of the card? It does and every time …

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Re: 486 will not boot from floppy; will not read from floppy either

Posted on 2021-05-01, 03:33

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by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Do you know if those DREQ and IRQ jumpers change anything? They don't seem to change anything at all when moved around. n IMD, does the capital 'Z' at the top of the screen (where it says fwRZd) change to lower case if you move the heads off of track 0 (try pressing '+' to go up one track and '4' …

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Re: 486 will not boot from floppy; will not read from floppy either

Posted on 2021-04-29, 00:47

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by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

[edit bad phrasing here] One differences I spotted is the hard wired link for 1x CPU multiplier on JP1 down by the BIOS chip. It's currently wired as 2-3, which the silkscreen says is 1x and the dosdays listing shows as 2x. What does IMD http://dunfield.classiccmp.org/img/index.htm do on either the …

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Re: 486 will not boot from floppy; will not read from floppy either

Posted on 2021-04-28, 01:44

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by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

What happens if you try to format a floppy, with no command line switches? Does it say what capacity it's going to try before failing? Had an odd case on another thread where the BIOS menus had the correct settings, but the registers ended up with the drive as a 360k 5.25". It will format as 1.44mb …

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Re: 486 will not boot from floppy; will not read from floppy either

Posted on 2021-04-27, 13:41

by

by CelGen

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I'm not using a CF card. I'm using a DOM. Anyways for the purpose of testing the entire IDE ribbon cable is unplugged and only one floppy drive is attached and configured in the BIOS.

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