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Re: TM32 - elegant standalone MT32Pi synth

Posted on 2025-04-02, 21:55

in Marvin \ Sound

in Marvin \ Sound

Would the midi cable with the DIN connectors work with an old keyboard switch like this? https://www.cablesonline.com/abmonswitbox1.html It may, if the said box simply switches between connectors pin-for-pin. MIDI only uses pins 4 and 5 on the DIN connector. One possible complication however is …

Re: BIOS checksums

Posted on 2025-01-23, 19:16

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

In many older BIOS versions, the option code scan goes to 0xF800 In others, it stops at 0xF400 I took a gamble, and it didn't pay out.

Re: BIOS checksums

Posted on 2025-01-23, 10:18

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Is it Ami? Phoenix? Award? There are tools to add option roms. I've thing to be aware of, there's a signature for oproms. They have to start with... 55aa Iirc. It's neither. It is a very special custom ROM made by Philips for a Magnavox 386 computer. Yes, the configured XTIDE code I used has the …

Re: BIOS checksums

Posted on 2025-01-23, 10:15

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

jakethompson1 wrote on 2025-01-23, 02:24: Option ROMs have to be on a 2KB boundary to be detected during the POST scan. Yes I made sure it was. I actually made 2 versions because I had 2 2k-aligned spots to place my code at, neither worked. One was 0xF780, the other 0xF800

Re: BIOS checksums

Posted on 2025-01-23, 02:12

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Well, anyway reporting back. It didn't work. Got the correct chips, wrote my custom image to one, it boots but my embedded XTIDE is not getting activated. Oh well it was a good try.

Re: 286 Board still green after vinegar and baking soda. What next?

Posted on 2025-01-22, 12:22

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

You may try a little ammonia over the green corroded traces, it dissolves copper compounds quite well. Don't let it sit there too much, only a few minutes then wipe it away, wash first with water then apply a little vinegar again and then once more water. It will not fix anything but will remove the …

Re: SD Cards Suddenly Becoming Harder to Find?

Posted on 2025-01-21, 23:23

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

(I did, when I was in Scotland a couple of months ago; the only thing I found edible there were garlic shrimp 😜 )

Re: 386 board dead?

Posted on 2025-01-21, 22:35

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Not necessarily the cache itself. Could be traces from cache to chipset, connections from those traces to either the cache chips or the chipset... Probably the first thing I'd do is reflow the chipset. The legs on that chip are likely to detach from the underlying pads and make bad contacts.

Re: SD Cards Suddenly Becoming Harder to Find?

Posted on 2025-01-21, 22:16

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Here in the US they are not hard to find, including in brick&mortar stores... I use a chain store brand, MicroCenter... sometimes I go there to pick up stuff in person (if I have other stuff to pick up too, it's not particularly close to me) but more often I just order their SD cards from Amazon, …

Re: BIOS checksums

Posted on 2025-01-20, 02:47

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Actually... I think I have a (partial) answer. It looks like the W27C010 chips I was using for testing are not pin compatible with the S27C1001 that the original BIOS is in. 🙁 I ordered a few of the latter and willl have to test again, this time hopefully with the right pin-compatible chip.

Re: BIOS checksums

Posted on 2025-01-19, 14:57

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Hmm, I found this project https://github.com/kpanic23/QB-checksummer ran the tool on a few bios files which I know have a good checksum and it said they are valid Then I cut the system BIOS part from that composite file above and ran the tool on it, it says good checksum Then I did the same with my …

BIOS checksums

Posted on 2025-01-19, 12:42

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I am trying to modify a BIOS and I think I'm failing because I end up with an invalid checksum. It's not a change in the BIOS code itself, I am just adding a small piece of code (an option ROM) inside the main BIOS file in an otherwise empty area. I made sure to align it properly to 2k, not change …

Re: sound card wavetable board

Posted on 2024-11-04, 13:27

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

That's not confusing at all 😀 I've never seen "x2" used like that. The usual is "+1"

Re: Can u pls help identify motherboard? Detects 64MB SDRAM as 16MB?

Posted on 2024-11-04, 13:24

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Problems with high-density vs low-density RAM are not confined to this period. For instance I have an Apollo Pro 133T motherboard (QDI Advance 10T) that recognizes high-density 512MB PC133 DIMMs as only 128MB.

Re: 386 Clock Generator Replacement

Posted on 2024-11-04, 10:26

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It's a nice project. I've done something similar with a SI5351 frequency synthesizer controlled via an arduino.

Re: Bought these (retro) hardware today

Posted on 2024-11-02, 01:13

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Got a QuadroFX 1300, aka GF PCX5900. A FX5900 with PCIe bridge. Works great in XP on my G41 motherboard, just tested. Need to test in win98 too. It's funny how the card runs relatively cool, but the bridge chip is very hot despite the big heatsink it has on. May have to rig a fan blowing on it.

Re: Modifying the POD83's voltage regulator for overclocking

Posted on 2024-10-30, 16:42

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Diode dropout voltage varies with current, and also with the junction temperature. The variation is direct with current (higher current = higher voltage drop) and inverse for the temperature (higher temperature = lower drop). You are probably seeing a combination of the 2 effects.

Re: Bought these (retro) hardware today

Posted on 2024-10-29, 17:39

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I think there's a clone of GORILLA.BAS for CP/M so at least there's that 😀

Re: Bought these (retro) hardware today

Posted on 2024-10-29, 17:13

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I *almost* grabbed an Osborne 2 off a local craigslist post a few years ago... but the seller didn't respond to my message 🙁

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

Posted on 2024-10-29, 15:06

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I am somehow in a "speaker drought" meaning I thought I had dozens of little 8 ohm speakers around, the type to hook up to speaker headers, or for general low-fi noise. They all seem to have disappeared, or I have at some point, put them "somewhere safe" effectively disappearing them. There's a …

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