retrocanada76 have you received yet dreamblaster's version?

retrocanada76 wrote:

It must be VGA Standard. 1280x960 is SVGA...

How many people here are actually using fixed frequency VGA monitors? I'd say the majority are using flat panels or modern CRTs. My oldest CRT dates to 1987..... even that is multi-frequency (a NEC Multisync II).

I have several VGA monitors that can't do 1280x960...

Hey, I see a lot of game shots used as tests, but test patterns are usually better to judge color accuracy and scaling issues. Apologies, but may have forgotten to announce that I added a lot of monitor and capture calibration and test patterns to the CGA Compatibility Tester specifically for testing converters like this. Geometry, colors, motion test, moire patterns, and a few more were added about 18 months ago. Latest version is always here: https://github.com/MobyGamer/CGACompatibilityTester/releases

As the name implies, it's only useful for generating CGA test patterns, so Hercules and EGA 350-line tests will have to be done with other programs. I was in talks with the 240p Test Suite project coordinator to port it to DOS and support all major graphics standards, but I have more projects than time at the moment.

@MobyGamer
wow a port of the 240p test suite will be great! I use the megadrive port all the time to calibrate screens , really useful!

@retrocanada76
I just updated to the latest firmware but for me low-res EGA is still reported by my monitor as 720x400@70hz

edit:
just checked 720x480 mode, the monitor reports it as 640x480 for some reason but this means that I don't get 720x480 on low-res ega games with the new fw

keropi wrote:

@retrocanada76 I just updated to the latest firmware but for me low-res EGA is still reported by my monitor as 720x400@70hz edit […]
Show full quote

@retrocanada76
I just updated to the latest firmware but for me low-res EGA is still reported by my monitor as 720x400@70hz
edit:
just checked 720x480 mode, the monitor reports it as 640x480 for some reason but this means that I don't get 720x480 on low-res ega games with the new fw

It's analog video. There is no way for the TFT monitor to know how many pixels per line is sent to it, 640, 720 or any other amount of pixels.
Which means that 400-line 70Hz mode is assumed to be VGA text mode by the TFT monitor so it chooses to sample 720 pixels, and 480-line 60Hz mode is assumed to be VGA graphics mode by the TFT monitor so it chooses to sample 640 pixels.

My 1280x1024 TFT monitor has special button combination to select if 400-line 70Hz mode should be 640 or 720 pixels wide (720x400 for text mode or 320x200 graphics).
I don't know if it allows that with 480-line 60Hz modes.

^ I have my doubts about that, the scalers in modern sets are not "dumb" anymore like 10+ years ago.
At any rate that's really a side-discussion - I have reported my experience here , whether it's an issue or not we will see 😊

keropi wrote:

retrocanada76 have you received yet dreamblaster's version?

not yet

keropi wrote:

^ I have my doubts about that, the scalers in modern sets are not "dumb" anymore like 10+ years ago.

keropi wrote:

At any rate that's really a side-discussion - I have reported my experience here , whether it's an issue or not we will see 😊

OK - but I think others might find the information how TFT monitors *usually* work might be useful info for others who think there's something wrong with their monitors or converters, so I think I should write this down.

It's not the fault of the scaler really, they can do anything (as demonstrated by my 10+ year old Viewsonic which allows the manual selection of 720 or 640 pixels in 400-line 70Hz format).
It's the monitor firmware that measures HSync/VSync rates and polarities and uses that information to determine which standard video format is being transmitted and how to sample it (i.e. generate pixel clock from HSync with a PLL and setting how many clocks per Hsync there should be).

So to a monitor, HSync frequencies of all standard VGA formats are so close that they are virtually identical (31468.75 and 31468.89 Hz in theory at least).
So a TFT monitor must detect from sync polarities and VSync rate if this is a 350/400/480-line mode and choose how many pixels per line to sample before scaling that to panel pixels.

What usually happens with TFT monitors is the following:
-70Hz 400-line mode : sampled at 720 pixels, assumed to be the standard text mode so it's perfectly sampled (small text would look bad when sampled incorrectly at 640 pixels). Not optimal for 320x200 graphics though.
-60Hz 480-line mode : sampled at 640 pixels, assumed to be the standard 640x480 graphics mode. 320x240 tweak mode would look perfect. Not optimal for 360 or 720 wide tweak modes.
-70Hz 350-line mode : sampled at 640 pixels, assumed to be the standard 640x350 graphics mode. very rarely used with 360 or 720 wide tweak modes so I would not worry about it.

Therefore, usually:
-70Hz 400-line modes are not 640 pixels wide according to TFT monitors
-70Hz 350-line modes are not 720 pixels wide according to TFT monitors
-60Hz 480-line modes are not 720 pixels wide according to TFT monitors

Modern TFT monitors work around this by not supporting 70Hz modes via digital interfaces - or the fact that digital interface does carry information about pixels per line 😀

One solution is to scale to larger formats, but it creates also other problems.
Even if EGA 320x200 60Hz is upscaled to standard 800x600 60Hz for monitor, the TFT will again scale that to native panel size.

^ shouldn't the refresh rate at least be correct on the OSD?
I need to find something that outputs a 60hz signal for sure, maybe I will try with the dreamcast to make sure the scaler is reporting things fine - at least refresh.

keropi wrote:

^ shouldn't the refresh rate at least be correct on the OSD?
I need to find something that outputs a 60hz signal for sure, maybe I will try with the dreamcast to make sure the scaler is reporting things fine - at least refresh.

Oh, you mean the monitor reports 75Hz? What is generating the test picture to the monitor in this case?

Yes, generally the monitor should be able to measure vertical refresh rate and horizontal refresh rate too, within some limits of accuracy of course.

So most likely video signal is actually is standard VESA 75Hz signal timings like the monitor says. It does not show the horizontal rate, but 640x480@75 should have 37.5 kHz rate.
Again, the monitor just has to assume based on timings that it's standard VESA format and it is defined to be 640 pixels.

That said, if it is not actually 75Hz format, it means that the monitor has measured the sync frequencies and amount lines per frame, but if the measurements do not match anything in its internal tables for supported video modes (within tolerance), so it's unable determine the exact format and may try to say something about it. Or just found a false match to that specific format.

retrocanada76 wrote:

Creating a new thread for the launch, any doubts about the project you can post here...

https://sites.google.com/site/tandycocoloco/m … -cga-ega-to-vga

Gerber files available and FGPA code released. Enjoy.

I am discovering this now - this looks like an excellent project! Last year I was wondering about doing something like that, because it would really help me having a secondary MDA screen when developing DOS software (I have a MDA card, but sadly no compatible display). Ultimately I had to cancel it because I couldn't find any solution for the missing MDA pixel clock (it's not present in the connector). I see you solved this problem beautifully, by sampling at much higher rates than the source MDA clock. I will try to assemble this as soon as I have some spare time, unless someone here would be willing to sell a ready-to-go unit at a reasonable price.

Thank you for sharing!

So I hooked up the Dreamcast on my monitor and it indeed recognizes the 640x480@60hz mode:

so that means that either something went wrong with the flashing of the 02-02-2018 update , or that the 60hz mode does not work for EGA or that my monitor just reports things wrong. From what my eyes tell me it doesn't look like 60hz is used since there is a little more jerky scrolling than usual.

@Jepael
at this point my friend I don't know what to think, I used UNIVBE's VBETEST program to display this resolution, maybe it indeed defaults to 75hz.
I am just reporting my experience so it can be potentially help with development.

keropi wrote:

I used UNIVBE's VBETEST program to display this resolution, maybe it indeed defaults to 75hz.

It does. It defaults to the highest refresh rate your card can produce for a given VESA-compatible mode, which may not be the default.

The best way to test is to run a program that just uses stock modes. FRACTINT is a good way to test since you can switch modes while the program is running.

^ can't find how to make it display 720x480@60hz
I will try some win9x stuff should be easier

The Dreamcast outputs 720x480@60hz, but only uses 640px wide framebuffer area. Your monitor is detecting it as standard VGA 640x480.
http://junkerhq.net/xrgb/index.php?title=Dreamcast
http://pms.hazard-city.de/ossc_sampling.jpg

well I tried TombRaider III with software rendering at 720x480@60hz under windows and the monitor still displays 640x480@75hz so I guess all that was for nothing....
thanks all for your help!

@retrocanada76 - from your website I understand that you are working on a new, improved v2.0, so I will probably wait for that before assembling anything. One humble suggestion I would have: is there any chance that the v2.0 could come in a "MDA only" variant? This would be nice for people (like me) that do not care about EGA/CGA, but are very interested in monochrome MDA/herc, while not being very handy with a soldering iron at the same time... I assume here that a MDA/herc-only version would need less elements (even if only a few resistors and dip switch).

mateusz.viste wrote:

@retrocanada76 - from your website I understand that you are working on a new, improved v2.0, so I will probably wait for that before assembling anything. One humble suggestion I would have: is there any chance that the v2.0 could come in a "MDA only" variant? This would be nice for people (like me) that do not care about EGA/CGA, but are very interested in monochrome MDA/herc, while not being very handy with a soldering iron at the same time... I assume here that a MDA/herc-only version would need less elements (even if only a few resistors and dip switch).

The 2.0 project is already on his site.
I am working on a version that can be factory assembled.
Lessons learned so far : for next prototypes, I will use better tolerance resistor networks, as the colors seem to differ a bit.
A prototype is on its way to retrocanada, for evaluation.
If it all works well, I'll have a small batch machine assembled.

dreamblaster wrote:

The 2.0 project is already on his site.

Yes indeed, but it also says 'If you are planning to build a new one wait just a little more, a new version 2.0 is under development.' - so I understood that there will be another (improved) "2.0"... but now that I re-read it, I probably misunderstood the phrasing. It would be strange to have two different "2.0" boards after all.

I am working on a version that can be factory assembled.

You mean, like on a single board, instead of having a FPGA core board + a daughter board? That would be cool.

If it all works well, I'll have a small batch machine assembled.

Any idea of the pricing level? Also, if you have some 'bad' versions with broken EGA/CGA but working MDA, I'd be quite interested. I see you are based in Belgium, so we are neighbours :)