It may be your monitor rather than the adapter. The low-res resolutions (350/400 lines and sometimes 480 lines) use a refresh rate of 70Hz which some monitors just reject.

Winstonwolfe wrote on 2026-02-19, 18:29:

Has anyone found a budget VGA→HDMI converter that reliably works with: […]
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Has anyone found a budget VGA→HDMI converter that reliably works with:

late-90s cards

Award BIOS text mode

I know high-end scalers exist, but I’m specifically hoping for something in the cheap Amazon/eBay tier that is proven to work.

This is a big challenge now.

I recently ordered cheap VGA-HDMI adapter from AliExpress, where older reviews mentioned DOS support.
I got latest revision with new MS9288C chip, but it doesn't work on Award BIOS/DOS text mode.

It's seems that older revisions had the AG02-EX chip, which really supports low resolutions, but such adapters are hard to find these days.
Re: What are the best Vga to hdmi scalers or peripherals for MS-DOS games ?

I went through this a few years ago. The problem is even if someone finds one that works, you ordering from the same listing can cause you to get something with a different chip that doesn't work.

I went all in on scalers, but even the more expensive GBS-C didn't always work with all PC signals.

I don't have a Retrotink 5x or 4K, so I can't say how they are. But the original non-Pro OSSC handles everything I throw at it. Sadly like everything else prices have gone up so they are even more expensive. But how many "cheap" $20-30 adapters do you go through that don't work before you hit the total price of something that handles whatever you throw at it.

SScorpio wrote on Yesterday, 13:37:

but even the more expensive GBS-C didn't always work with all PC signals.

I'm actually working on proper custom firmware for the GBS-8200 (i.e. runs on the onboard MTV230, not a bodged ESP add-on), supporting 15KHz modes (or anything else down to 10KHz) with separate H/V syncs can be done, let me know if there's something you need? Firmware can be flashed with an arduino nano or any other similar board with I2C.

jmarsh wrote on Yesterday, 19:01:

SScorpio wrote on Yesterday, 13:37:

but even the more expensive GBS-C didn't always work with all PC signals.

I'm actually working on proper custom firmware for the GBS-8200 (i.e. runs on the onboard MTV230, not a bodged ESP add-on), supporting 15KHz modes (or anything else down to 10KHz) with separate H/V syncs can be done, let me know if there's something you need? Firmware can be flashed with an arduino nano or any other similar board with I2C.

Have you looked into using the native digital output pins of the Tvia?

Link to project page?

jmarsh wrote on Yesterday, 19:01:

I'm actually working on proper custom firmware for the GBS-8200 (i.e. runs on the onboard MTV230, not a bodged ESP add-on), supporting 15KHz modes (or anything else down to 10KHz) with separate H/V syncs can be done, let me know if there's something you need? Firmware can be flashed with an arduino nano or any other similar board with I2C.

I did a dig through the pile and I did find an unused GBS-8200, I'll need to get a board to let me do the flashing. Do you have a Github or other location with your project?

maxtherabbit wrote on Yesterday, 23:09:

Have you looked into using the native digital output pins of the Tvia?

That's a bit beyond the scope... it's a lot of pins and they're very small, so not really feasible without a board redesign. Would have been nice if whoever made those "GBS HD 9800" boards had done that and used a DVI/HDMI encoder instead of just bodging a VGA->HDMI chip in there.
I have discovered the composite sync separation on the MTV230 is garbage. So the original firmware only uses it when in RGB-HV mode, and it can't properly detect Hsync below ~24KHz. So that's why it doesn't work with 15KHz HV sync signals. But there's no problem using the TVIA to query the frequencies instead, just like how it is done when in RGBS or YPBPR mode.

There's a repo here but I've been slacking about pushing the changes because I honestly doubt anyone would currently find it usable without specific hands-on instructions. Since the chip can only be flashed via ISPC mode (unless anyone happens to know the magic pin config to make it boot into parallel programming mode?) flashing new firmware comes with a risk of bricking. I've tried to minimize it as much as possible by not erasing any used pages and not modifying any code before the first check of the "break" jumper, but things can still go wrong. It's also possible there might be GBS-8200s out there with completely different default firmware than what I've seen, which means the patches/hooks won't work.
I also want to keep it reasonably quiet at least until I get a splash screen stating the firmware is not to be sold.

SScorpio wrote on Today, 00:22:

I did a dig through the pile and I did find an unused GBS-8200, I'll need to get a board to let me do the flashing. Do you have a Github or other location with your project?

I don't have auto-input-detection working yet, but if you want to let me know what sort of RGBHV input signal you want to feed it and what VGA resolution you'd like to get out of it, I could try hardcoding something.

If you can find one, the old Sewell Hammerhead active VGA to HDMI works pretty well. I use it to connect my 5x86 system to a 32" 1366x768 Samsung TV on the HDMI2 input and so far all the DOS games look fine as does the boot and Ami BIOS screens, but Windows is slightly oversized so a little of the taskbar gets cut-off. Your results may vary depending on your monitor possibly.

https://sewelldirect.com/blogs/learning-cente … dio-hdmi-to-vga

386DX40 wrote on Today, 00:59:

If you can find one, the old Sewell Hammerhead active VGA to HDMI works pretty well. I use it to connect my 5x86 system to a 32" 1366x768 Samsung TV on the HDMI2 input and so far all the DOS games look fine as does the boot and Ami BIOS screens, but Windows is slightly oversized so a little of the taskbar gets cut-off. Your results may vary depending on your monitor possibly.

https://sewelldirect.com/blogs/learning-cente … dio-hdmi-to-vga

I found that this one has little to no low pass filtering and will put a lot of noise in the output on noisy systems

Interesting. On my particular system the output looks great, but I should try it with one of my ISA cards that looks crappy on my little test bench LCD monitor (jail bars & noise) and see how the Sewell handles it. The only VGA I've ever had connected to the Sewell is a WD 90C31 made by Paradise with a Sierra Hi-Color RAMDAC.

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I found that this one has little to no low pass filtering and will put a lot of noise in the output on noisy systems
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