Re: Mitsubishi 386 crashed going into protected mode

Posted on 2022-05-03, 19:04

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Cache is used always, not just in protected mode, but the access pattern are different and that might be enough to expose a problem with marginal SRAM chips. It has to do with the registers being, by default, only 16-bit wide in DOS and 32-bit in protected mode. I too found that 16-bit/DOS code …

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Re: Floppy Drive capability question.

Posted on 2022-04-27, 20:39

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

My question is, can I use a 1.44mb 3.5 drive, to read/write floppies of that capacity or lower, and same for 1.2mb 5.25 drives to read/write floppies that are that capacity or lower? Or do I need dedicated drives for the smaller capacities? I may have to format the floppies as well, so the same …

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Re: Panasonic JU-475-4: issue with 5.25 floppy disk

Posted on 2022-04-26, 11:48

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

As a rule of thumb if the floppy has an extra ring attached to the central hole, where the media is clamped to the spindle, it's a DD disk. Also that self-made write protect hole is a giveaway this particular floppy was used in 1-sided drive and flipped. So there is a good chance those are 1-sided …

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Re: Heatsink/Fan for 486DLC/E

Posted on 2022-04-25, 11:48

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I've got a motherboard with a TX486DLC/E processor on it. I did some research and from what I understand, a heatsink is highly recommended, and a fan would be even better. My question is, how would I find a heatsink/fan for such an old model? Is it really unwise to use the PC without any form of …

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Re: 5.25 FDD TEAC FD-55GFR advice

Posted on 2022-04-23, 10:23

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Dirt and dust inside the drive - pretty normal for that age and use, in fact other than rust it's not all that dirty. Compressed air might do the job if the dirt is not "cigarette glaze" (sadly, if often is) or otherwise very sticky. Heads might need cleaning as well - I'd do it anyway, unless …

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Re: crappy old power supplies

Posted on 2022-04-21, 20:24

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

There is filtering if you look closely, starting inbetween the heatsinks, to the right of the second photo. Plus the one on the AC receptacle. Eh, this isn't even a modular PSU, I take that back, I got confused by all the AC sockets. It looks like it has one input and two outputs for some reason, …

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Re: crappy old power supplies

Posted on 2022-04-21, 14:18

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Great example of what I meant - big heatsinks but poor PSU. AFAICT it's an old analog design with medicore efficiency - in fact it looks like most of the AC input filter is missing to save a few cents on the manufacturing costs, and there isn't any PFC I can see either. Because it's modular but the …

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Re: Degaussing floppies

Posted on 2022-04-20, 21:11

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I have not, but the magnetic degradation of a floppy stored in a box is very slow. I don't expect any of them to fail after just a month or two. I suppose one can get a "false positive" when a damaged floppy seems to format fine after some treatment but then fails read/write soon after. Haven't …

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Re: crappy old power supplies

Posted on 2022-04-20, 20:57

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

As in "as long as this part here where we conveniently situated the fan control circuitry doesn't get any warmer than x, the most vulnerable bit of this PSU will not get warmer than x+n, based on testing, calculation and experience". This is all fine in theory but the conventional wisdom is to …

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Re: crappy old power supplies

Posted on 2022-04-20, 10:47

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Cuttoon wrote on 2022-04-20, 10:13: why would you put the temperature sensor on the heatsink? The heatsink doesn't mind to be hot, as a matter of fact. The heatsink might not mind, but the diodes (or switching transistors) bolted to it do 😀

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Re: Degaussing floopies

Posted on 2022-04-20, 10:29

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

degaussing a floppy won't improve results over just trying to reformat it without degaussing it in-between I have a bunch of second hand floppies, which I had to clean with water and IPA first (I mean the magnetic surface, though the envelopes were dirty too) to remove weird stains, dirt, and …

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Re: crappy old power supplies

Posted on 2022-04-20, 10:04

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Eh, I'm starting to think some people posting about "crap PSUs" haven't actually seen a low quality PSU. This is what the bottom of the barrel looks like: IMG_1530.JPG And yet it works, even in this state, so I'll probably end up using it for less important projects, of which I have many. BTW, the …

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Re: ESD and you

Posted on 2022-04-15, 09:35

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

ESD protection is much more important when handling individual parts. People keep talking about voltage and whatnot but the thing to worry about is charge/energy stored on human body. There are models for that (though in winter with very dry air and a lot of clothing being worn, you want the very …

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Re: Upgrading SMD Cx486SLC/e-33MP

Posted on 2022-04-15, 09:18

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I don't have any Cyrix SLC2 chips so I have no idea how much performance the clock doubler provides with limited 1k cache. Probably not much. But there is a point toi using clock doubler on TI SXLC(2) - sure, it won't be x2 gain, or even close to it, but we are talking about replacing the soldered …

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Re: Upgrading SMD Cx486SLC/e-33MP

Posted on 2022-04-14, 17:12

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I can't find that ebay listing now but the chip looked odd. All 386SX-class CPUs come in the PQFP-100 package with those wings at the corners. This one didn't have them.

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Re: Degaussing floopies

Posted on 2022-04-14, 09:23

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

That's why the field strength needs to be slowly decreased, or faded out, to prevent leaving any areas with one particular magnetic orientation. That being said, you can always repeat the process (as many times as you want/need) if R/W to scrubbed floppy fails, and frankly it's rather hard to create …

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Re: Upgrading SMD Cx486SLC/e-33MP

Posted on 2022-04-14, 09:04

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

IMO the upgrade to 8k cache is not worth the trouble, unless it's a "project" - that is, it's more about trying to do it rather then expecting a decent performance boost. The sad truth is internal cache in these DLC-type CPUs is not all that fast (mostly due to rather narrow 32-bit bus). Plus you …

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Re: Degaussing floopies

Posted on 2022-04-12, 21:11

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by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Depends on how dead the floppy is - I've "repaired" quite a few floppies with my magnet. Sometimes it takes a few tries to get rid of all bad sectors but if it still fails to format on particular % of progress after 3-4 times then you have a damaged surface and that's it. If it's a pre-owned floppy …

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Re: Degaussing floopies

Posted on 2022-04-12, 19:23

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I was wondering if anyone has experience in attempting to 'reset' the magnetisation of the disks with a degausser? I do it with strong permanent magnet. Any modern magnet will do in most cases, I use neodymium one from a broken HDD but a magnet from a speaker would work as well. It has to be strong …

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Re: Would you fix an old Power supply? or just buy a brand new one?

Posted on 2022-04-12, 17:08

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

You can check TME as well (tme.eu) - while their stock/selection isn't as great as Digikey, they might have better prices. For small orders the shipping should be cheaper as well since it's inside EU.

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