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Screen Resolution

Atari Notes
Published November 1995

This month Ofir Gal takes a look at screen resolution.

One of the reasons for the success of the Atari ST in the MIDI market was its clear, high‑resolution display. While Macs were too expensive, and PCs had a shoddy green text on black display, Atari users were enjoying high‑quality, monochrome graphics with all their benefits.

About Display Resolutions

What might seem obvious to the computer buff may not be so to the musician, and screen resolution is one of many examples. Computer display is basically measured by four factors — height, width, number of colours, and refresh rate. The first two are not measured in inches or centimetres, but in picture elements called pixels — the tiny squares that make up the picture on your computer screen — and each pixel takes up 1 bit of computer memory. The ST hi‑res mode is made up from 640 x 400 pixels, requiring 256,000 bits, and since each computer byte is made of eight bits, this translates to 32,000 bytes, or about 32Kb of RAM. The number of colours varies from monochrome through greyscale to true‑colour. As the number of colours is increased, so is the memory required to display each pixel — while a monochrome display requires 1 bit per pixel, a true‑colour one would need 24 bits. The general compromise is to use 8 bits per pixel, which translates to 256 colours — this is suitable for most needs, with the exception of graphic design and colour reproduction work. It doesn't take a NASA scientist to see that a colour display would require eight times more RAM — 250Kb to be exact.

As you can see from the screen grabs, higher resolutions are desirable, and a little extra screen estate can go a long way. It can mean less scrolling, as you can see more tracks, and more parts on screen. If you have considerably more screen pixels, you can start working with multiple windows. It's not the physical size of the screen that is the issue, but the number of pixels that can be squeezed into the display area. Obviously, there comes a point where the pixels are so small that the image is all blurry, but a good quality monitor can achieve much more than you'd expect.

The refresh rate, also known as vertical scan rate, indicates the number of times the display is updated, and the faster it is, the better. Standard (and now obsolete) VGA screens had a refresh rate of 60Hz, which resulted in subtle, but persistent flicker that tired the eyes. Refresh rates above 70Hz are much easier to work with for long periods of time, and many PCs are now equipped with graphics cards capable of screen resolutions of 800 x 600, and a refresh rate of 75Hz.

ST Resolutions

The ST can only generate three resolutions, known as ST High, ST Medium, and ST Low, all requiring the same 32,000 bytes. As can be seen from Table 1, as the number of colours is increased, the resolution is decreased by the same factor. It is also obvious why the monochrome display works so well — with a healthy refresh rate of 71Hz, it is easy on the eyes compared with the old 60Hz VGA standard.

The high resolution mode is ideal for word processing, DTP, and, of course, MIDI, enabling the display of a musical score and fine detail. However, it only works with a monitor designed specifically for the Atari. The other two screen modes are not available when using this monitor, and are only of use for playing games, or very basic image editing.

Compared with today's computers, the basic ST resolutions are not that impressive, but there are ways of improving them with the use of simple modifications, or more expensive graphic cards.

To get the most out of graphics but still remain an Atari user, consider buying a TT. This machine was overpriced when it was launched by Atari, but a second‑hand one can be obtained for a fraction of the original price. Besides the vastly improved performance, the TT is capable of a resolution of 1280 x 960 pixels when connected to the SM194, an Atari‑made 19‑inch monochrome monitor. When used with a standard VGA monitor, the TT can display various screen resolutions, including a rather useful 640 x 480 in 16 colours.


The ST does not make full use of the SM124 screen (the image is surrounded with a black border), so a clever hardware hack was developed to increase the screen resolution, and make use of the unused screen area. Overscan was originally a public domain DIY kit, comprising a text file and a few images outlining the modifications to the ST motherboard. The idea was refined, and made into a commercial product. How far the display resolution can be pushed varies from one ST to the next, but resolutions of 688 x 480 and beyond are possible. Although it doesn't sound like much, this 30% increase in screen area makes a big difference, even though it uses a little more memory — around 40Kb instead of the usual 32Kb. Overscan works with all ST, STM, STF, STFM, and MegaST models, but due to changes Atari made when designing the STe and MegaSTe, there is no way of increasing the resolutions on these models. Note also that Overscan is compatible with Cubase, but not with Creator/Notator.

Overscan is available from Compo UK (Tel: 01487 773582) for £49.95. Installation requires good soldering skills, but Compo will do the modification for you for an additional fee of £20.

Graphics Cards

The MegaSTe and TT feature a VME buss that can be used to connect a graphics card. The capabilities of such cards are normally indicated by the amount of Video RAM they come with — a 1Mb card can normally produce a screen resolution of 1,024 x 768 at 256 colours. The Nova range starts with a 1Mb model retailing at £399, and extends to a 4Mb model that sells for well over £1,000. The Falcon Nova should be available by the time you read this, and this finally frees the Falcon processor of the thankless task of screen refreshing.

The Nova cards are available from 16/32 (Tel: 01634 710788). Although earlier versions of Cubase worked perfectly with the cards, for unknown reasons Steinberg made some changes in v3.10 and Cubase Score that prevents Cubase from working.

The Megabus And MEGA4000

The latest addition to the graphics scene are the MegaBus and Mega4000 cards, available from 16/32 and System Solutions (Tel: 0181 693 3355) respectively. The MegaBus costs £399, while the Mega4000 price has not been set yet, but should be under the £300 mark. System Solutions have indicated that the Mega4000 is capable of true‑colour display at 640 by 480, or 1151 by 896 in 256 colours. As with other graphics cards, these are incompatible with Cubase, as well as Creator and Notator.

System Solutions have indicated that an ST/STe graphics card is imminent, but there are no further details available at present.

Screenblaster And Blowup 030

If you have a Falcon, devices like Screenblaster or BlowUp 030 can help you utilise the full power of your computer. They consist of a small adapter that plugs to the monitor port of the Falcon, and a simple AUTO program. Depending on the type of monitor (a multi‑scan SVGA is recommended), resolutions such as 832 x 624 or higher are possible. Screenblaster is available from Compo UK for £69.99, and BlowUp 030 from System Solutions comes in several versions starting at £15. The full version costs £69.95.

Table 1 — Those Screen Resolutions In Full

 ResolutionColourRefresh Rate
ST High640 x 400271Hz
ST Medium640 x 200450/60Hz
ST Low320 x 2001650/60Hz
TT High1280 x 960270Hz
TT Medium640 x 4801660Hz

Audio Spector

Audio Spector is a new product from Steinberg that realises the full potential of the Falcon as a pro‑audio tool. It is both an accurate level meter and spectrum analyser, with advanced features like a stereo phase correlation meter.

The program works either by using the Falcon built‑in A/D and D/A converters, or via the FDI (Falcon Digital Interface). It is centred around three windows, each with its own menu bar and related dialogue boxes. The first is the level meter which can be switched between RMS and Peak display, and has an adjustable headroom. Scaling can be set to conform to the BBC BS5428, or the German DIN 45046 standards. The meter has adjustable peak hold and fallback times, and threshold and clipping counters.

The spectrum analyser window is divided into 30 bands, from 25Hz to 20kHz. Like the level meter, it features adjustable peak hold and fallback times. When used with the test tone generator and a graphic equaliser, it can be used to fine‑tune the acoustics of a studio. The test tone generator can produce sine waves at any frequency, or white noise.

The program requires a Falcon with a high‑resolution display (640 x 400 or better at 16 colours), and 4Mb of RAM. It is copy‑protected, using a cartridge port dongle, and is available from Harman (Tel: 0181 207 5050) for £399.00 inc VAT.