Living With Amiga Video Modes

by Eric Schwartz
From The AmiTech Gazette
Dayton, Ohio
May 2020

Welcome to yet another month in plague world, everyone! Hopefully the lot of you are staying as healthy and safe as possible in “these trying times,” not to belittle anyone who’s been hit directly by the virus or has to risk their neck on a regular basis working in the medical or service industries. Certainly things will improve over time, or enough hardcore capitalists will decide the living population is less important than a sagging stock portfolio, and wind up killing us all. Either way, good luck to the world. At least we found out the environment can improve surprisingly quickly when fewer humans are out there mucking about.

Speaking of staying home, this month’s meeting will once again be held ‘virtually,’ using Discord (www.discordapp.com, or get the Discord app for your mobile device.) Watch your e-mail for a link sent by prez Mike Barclay which will invite you to the AmiTech Discord server, which should arrive a day or two before the meeting date. If you’re not sure about this, or just don’t want to wait around, send Mike a mail yourself, and he’ll send you an invite link. Hope you’ll be able to drop by this time.

In the world of the Amiga, a frequent issue for hardware users is finding a suitable screen, now more than ever. Originally, the Amiga came from the days when home computers were frequently expected to be hooked up to televisions, and the dedicated monitor was more of a luxury for those with an obsession over a sharp picture with consistent color. Most Amiga screen resolutions were built around the scan rates of NTSC and PAL video signals, even when output to a monitor. Later, as hardware became less expensive and PCs with VGA video cards became more prevalent, the 31 kilohertz VGA-style scan rate became its own standard, and allowed for a nice solid 640x480 display.

Meanwhile the Amiga had a solid 200-line display (240P) or an interlaced 400-line display (480i) that would flicker as fields were alternated 30 times a second, the effect being more obvious depending on the level of brightness or contrast. Some Amiga video enhancements were ‘flicker fixers’ which buffered the display and converted it to a 31 Khz signal, for the Amiga 2000 and built in to the A3000.

Starting partially with the ECS chipset Amigas and going whole hog with the AGA models, Amiga video display modes became more malleable, and through software and tweaking an Amiga could display to NTSC, PAL, VGA, and several other possible resolutions or scan rates and switch between them at will. The Amiga, especially AGA models, were pretty unique in that regard, the downside being that you would require an equally versatile multiscan monitor if you hoped to view more than a small range of them.

The high-res, high-scan rate modes were taxing to the Amiga’s chips, and didn’t have the same performance as a pedestrian NTSC mode, and AGA systems didn’t offer a built-in flicker fixer either, so the next step up is adding a new video card such as Cybervision, Picasso, or newer ones like the ZZ9000 or SAGA/Vampire. These allowed for high-resolution screen modes with up to 24-bit color depth with quicker performance than a similar AGA display. The downside coming from it being a separate system than the dedicated Amiga graphics, so if you want to use both, you’ll need either separate monitors depending on mode, or some kind of switch or pass-through, whether external or built into the video card. Your productivity software may work best on a 24-bit CybergrafX or Picasso96 display, but if you want to play a game, it will likely insist on a ‘classic’ NTSC/PAL (probably PAL) display.

The problem is magnified by the fact that monitors for an NTSC or PAL-compatible signal are getting older and harder to come by. The flat-screen, wide-screen, digital highdefinition LCD/LED monitor or television is the standard of the day, and the newer they are, often the less tolerant they are of older signals and connections. Some still offer analog connections for RF/antenna, composite, or component video formats, which help, but are not ideal viewing quality for an Amiga display. Many monitors still take VGA video connections, and the classic Amiga RGB-toVGA converters are still fairly common. What isn’t as common is a modern monitor which accepts a signal below 31 Khz VGA scan rates, limiting you to specific scan rates or video expansion displays, There are some monitors out there which do accept a 15 Khz signal, though maybe not in the best way. Interlaced screen modes can be less appealing than on a CRT monitor, thanks to the differences in display tech.

The remaining option is to invest in a video scan rate converter of some type. These range from low-quality Chinese-made devices for as low as $20, to internal boards which do the ‘flicker-fixing’ before sending the signal out, up to the larger external converters with more bells and whistles for possibly hundreds of dollars. Each has their own advantages and drawbacks, and your own mileage may vary depending on what screen mode from what system you try to output to what monitor or TV. You’ll probably have to appraise and limit the screen modes you use on your Amiga. Your LCD monitor or your scan converter may be versatile, but few handle all Amiga modes, from NTSC 240P to PAL 576i to Productivity mode to video card modes to those strange 24 Khz modes some used to get higher resolutions.

Especially if they have a compatible monitor or converter, few Amiga users probably need more than a VGA-style screen resolutions for productivity, and NTSC/PAL modes for games and other software that doesn’t accept other modes. Since I got my scan-doubler device from RetroTINK.com. I can use my Samsung LCD TV to display NTSC and PAL displays very well (albeit upconverted), and video card displays, such as from the Amiga 600’s Vampire card, can go in via a different HDMI input. Maybe some day it will all come through one wire without any issues, but that’s a problem for future me. I can see why some would rather do their Amiga work exclusively thru emulation, as they wouldn’t have to put up with these video issues. Well, they do, but not necessarily in the same way.