This image shows a CosmosEx screencast of an Atari Mega STe in high resolution.

Throughout my Atari ST-owning life, I have only ever owned Atari’s color monitor, the SC1224. It can display two of the ST’s video modes: low resolution (320×200, 16 colors) and medium resolution (640×200, 4 colors).

The Atari also had a 640×400 high resolution mode, but it required a different monochrome monitor.

I never had a mono monitor, but recently I came across some high-res software I wanted to test. What to do?

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Finding a way

I immediately thought of the CosmosEx and its “screencast” function, which lets me see and control my Atari Mega STe remotely via a web browser. I thought: what if I turn off my monitor, so the ST doesn’t know what sort of monitor is attached, and then run it remotely via the CosmosEx screencast function?

I tried this idea, but alas, it didn’t work. The “ST High” option remained grayed out among the “Set screen resolution” choices.

So, I asked on atari-forum, and AdamK pointed out that the ST detects the presence of a monochrome monitor when the MONO DETECT signal is connected to the GROUND.

I looked up a fantastic wiring diagram of the Atari Video Connector, and found that pin 4 is MONO DETECT, and pin 13 is GROUND.

This photo shows a wire connecting pins 4 and 13 of the Atari Video Connector, tricking the Atari into thinking a monochrome monitor is attached.

I decided to try connecting these two pins with a wire. But first, I copied CE_CAST.PRG into the AUTO folder on my boot drive to make sure the screencast function would be available since my monitor would be disconnected. (I normally load CE_CAST on demand, rather than boot with it, since it can conflict with programs.)

Make sure that CE_CAST.PRG is copied into your AUTO folder first.

After that, I disconnected the monitor cable, inserted the wire, rebooted the Atari, then launched the screencast webpage in a browser on my Mac.

Voila! It booted into monochrome!

This is awesome. The screencast can be a bit stuttery, and the mouse is hard to control, but it works! Best of all, I didn’t have to buy a second Atari monitor.

Cite this article

Renaud, Josh. “Using high res on my Atari ST with the CosmosEx and a wire.” Break Into Chat, 11 February 2019, https://breakintochat.com/blog/2019/02/11/using-high-res-on-my-atari-ste-with-the-cosmosex-and-a-wire/.

Other citation formats

MLA

APA

Renaud, J. (2019, February 11). Using high res on my Atari ST with the CosmosEx and a wire. Break Into Chat. https://breakintochat.com/blog/2019/02/11/using-high-res-on-my-atari-ste-with-the-cosmosex-and-a-wire/

Chicago

Renaud, Josh. “Using high res on my Atari ST with the CosmosEx and a wire.” Break Into Chat. February 11, 2019. https://breakintochat.com/blog/2019/02/11/using-high-res-on-my-atari-ste-with-the-cosmosex-and-a-wire/.

BibTeX

@online{renaud2019using,
  author       = {Josh Renaud},
  title        = {Using high res on my Atari ST with the CosmosEx and a wire},
  year         = {2019},
  month        = feb,
  organization = {Break Into Chat},
  url          = {https://breakintochat.com/blog/2019/02/11/using-high-res-on-my-atari-ste-with-the-cosmosex-and-a-wire/},
  urldate      = {}
}

Wikipedia

{{cite web |last=Renaud |first=Josh |title=Using high res on my Atari ST with the CosmosEx and a wire |website=Break Into Chat |url=https://breakintochat.com/blog/2019/02/11/using-high-res-on-my-atari-ste-with-the-cosmosex-and-a-wire/ |date=2019-02-11 |access-date=}}

Comments

One response to “Using high res on my Atari ST with the CosmosEx and a wire”

denpashogai

May. 8, 2020

Looks great! If you can get a hold of a working SM125 monitor though, there’s something really charming about it, and they’re not huge (for CRTs, that is).

Using high res on my Atari ST with the CosmosEx and a wire

Finding a way

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