Re: 386 and Compact Flash Woes

Posted on 2023-07-17, 10:47

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The primary storage is a 512MB Compact Flash drive using IDE adapter I've successfully used with other 386 and 486 builds in the past. How do you mean? Is the IDE adapter tested on other systems, or the card? Or both? In my experience any CF card that has the removable bit set (and with it the …

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

Posted on 2023-07-16, 22:06

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

* Lubricated the 3 1/2 floppy drive (no more weird noise between track ~20 & 60) It's very rare for any floppy drive to require lubricating the head sled rails. These usually are meant to run dry (bronze bushings move over hardened, polished steel rods), but must be clean. There's very little slack …

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Re: 486 Overdrive upgrade

Posted on 2023-07-15, 23:25

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The extra pin on ODP does nothing, should not be connected internally to anything either. It's sole purpose is to prevent ODP installation into typical 486 socket (without excessive force anyway). The other way around, that is ODPR into ODP socket, that can be done, but Intel was "clever" and didn't …

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Re: Cpu write back cache causing issues.

Posted on 2023-07-13, 17:52

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Another curious find is an “Internal Cache WB Burst” option. A Write-Back of L1 cache data to the L2 cache or main memory is per definition a burst write. But this option allows to disable this. IIRC the Cyrix CPUs had, at first, their own WB protocol that was not compatible with Intel. I vaguely …

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Re: Cpu write back cache causing issues.

Posted on 2023-07-12, 11:42

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I mean all I know is that if I remove that one jumper from pins 6-7 of JP8 while all the other jumpers are the same everything works fine and CHKCPU program shows that it it has changed to WT mode. WT is way easier to implement than WB. So simply moving that one jumper is "fixing" the problem, yes, …

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Re: Cpu write back cache causing issues.

Posted on 2023-07-12, 10:08

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

so far I have figured out that jumper at pins 6-7 of JP8 changes between WB and WT cache modes It takes more than that to properly support WB on a 486 system, quite a few other signals must be connected as well - and perhaps aren't. Just telling the CPU to use WB instead of WT is not enough if the …

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Re: My Mb800h. I have no idea what I should do.

Posted on 2023-07-12, 10:03

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Put a CPU in it and run some extended memory tests maybe? Like memtest86, it will stress CPU and make sure the memory is good at the same time, several full passes will take hours to a day. It'll also test CPU to memory bus and quality of power supply because if anything is bad it will start causing …

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Re: 8 bit floppy controller jumper settings need HLC-630B and PE-510D

Posted on 2023-07-12, 08:40

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The left one has ROM jumper that should be on-board BIOS ROM enable/disable, and a bank of 4 jumpers to contol the drive types (when ROM is enabled I guess). The right one has 3 jumpers (one for ROM I guess and other 2 for address since it can have 2 channels) and 4 switches. The switches can be …

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Re: Strange capacitor on this Octek Jaguar IV-P 386

Posted on 2023-07-11, 11:10

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

1) Cheap way to fix some minor timining issue, like spurious spikes, under/overshoots or reflections on transitions. Usually you'd connect it to GND but +5V in such system is also pretty low impedance, so it could be because the +5V pin was easier to reach or a deliberate choice because it somehow …

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Re: Help needed with MIDI / MT-32 for DOS

Posted on 2023-07-10, 21:25

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by Deunan

in Marvin \ Sound

in Marvin \ Sound

Ooh, many thanks for that CM-32P pack, and the links, may whatever gods you belive in grant you many children. In the meantime I've tested the AWE64 card, seems to work but putting it into non PnP system requires running several init programs. I guess I'll keep it for something else and try to use …

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Re: Help needed with MIDI / MT-32 for DOS

Posted on 2023-07-10, 18:44

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by Deunan

in Marvin \ Sound

in Marvin \ Sound

So... for any PC not capable of running DOS 6+ and EMM386 I need actual intelligent MPU hardware - and I do have a 286 machine with MFM drive and DOS 3.31 that I wanted to use. I think I saw some projects that re-create Roland cards, will look into that. If I'm to spend so much money on ye olde ISA …

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Help needed with MIDI / MT-32 for DOS

Posted on 2023-07-10, 10:24

by

by Deunan

in Marvin \ Sound

in Marvin \ Sound

Good people, I'm sure this topic has been already covered many times but there's so many posts, different HW mentioned, and some conflicting info that I decided to ask this again. What I want: MIDI output in DOS on 286/386/486 class HW - think Sierra adventure games and the like. Cheap, no 300$+ …

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Re: Capacity of standard CD and CD-R

Posted on 2023-07-09, 22:20

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Thanks for the explanation. I come from the era of dcload IP dumping over the BBA, the concept of reading the disc in a PC drive is new to me. The physical attributes of the high density area were always a black box to me. Never had a BBA, too expensive, so I used the serial port with my own dumper …

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Re: Question regarding tantalum capacitors on old hardware

Posted on 2023-07-09, 17:36

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Tantalum are used in many circuits, not all of them are low-impedance vs power supply so in such cases a short will not cause it to burn up, the energy will be dissipated in some (usualy nearby) resistance. But even in this scenario they also can go shorted internally. Older dry tantalum were not …

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Re: Capacity of standard CD and CD-R

Posted on 2023-07-09, 17:27

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Is that the only thing that constitutes a "GD"ROM Higher bit density? Yes, and no. Yes because everything else is the same and in fact some standard PC CD drives can read the hi-density area once you fool them into thinking the loaded disk is just one long audio track - which is done with a special …

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Re: Capacity of standard CD and CD-R

Posted on 2023-07-08, 21:03

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Each second consists of 75 frames (aka sectors). That's what it is usually called by most people, but frames on CDs are entirely different thing and are 25 bytes long. I prefer to decode MSF to minutes, seconds and fractions (of a second) but then again I tend to think of CDs at a lower level and I …

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Re: Question regarding tantalum capacitors on old hardware

Posted on 2023-07-06, 22:16

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Tantalum caps on Socket7 mobo? Can we get a photo? I don't think I've seen them used past 486 mobos, except SMD but these are not round. Are you sure these are not electrolytics, maybe polymer ones? And yes, there are wet tantalum caps, these are quite different from the typical sintered powder (or …

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Re: Accidentally damaged FIC 3486-VC HD Motherboard

Posted on 2023-07-06, 22:04

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Bought this one: https://www.aliexpress.com/item/33023239239.html?spm=a2g0o.order_list.order_list_main.12.c5ff1802B3linG Yeah, I don't quite belive it has 100MHz BW, or 500Ms/s for that matter (or if it does it's a very small memory buffer), but it should do nicely. Does it come with 10:1 probes? …

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Re: Help needed: 486 Motherboard Repair (A-Trend ATC-1762)

Posted on 2023-07-05, 23:36

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Don't use a 74F04 instead of a 7406. While I agree I think there is another DIP chip next to that 7406 and it's a 74F04. Which would probably be part of some address decoding or maybe it's inverting a control line (RD, WR or some chip select). There is no need to use F in anything keyboard related …

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Re: Accidentally damaged FIC 3486-VC HD Motherboard

Posted on 2023-07-05, 23:27

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I don't have an oscilloscope to test the ISA A scope would be very useful here. It's not worth buying one just for this mobo but if you were planning to it's a good opportunity. Otherwise - if you really want to try and repair this board, or you are just looking for a "project" - maybe consider …

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