Classic Computer Magazine Archive Article from Compute! magazine

Amiga View

Charles Brannon, Program Editor

A New Operating System

Computer software continually evolves, and operating systems are no different. The operating system is the core software of your computer, responsible for managing the hardware and providing routines for other programs to draw upon. The Amiga operating system, for example, contains routines that support menus, windows, memory management, and multitasking.

Most computer operating systems are stored in Read Only Memory (ROM), a permanent, non alterable form of memory. In contrast, most application software is provided on disk, which is loaded into Random Access Memory (RAM). When updates to the software become necessary (which is almost always the case), the publisher can simply ship new disks.

The only way to upgrade software stored on ROM, though, is to pry out the original ROM chips inside the computer and replace them with new ROMs, This usually requires dealer servicing.

RAM Emulating ROM

The Amiga uses a different technique. It contains only a small amount of ROM which loads the bulk of the operating system from the Kickstart disk into a special area of RAM called the Writeable Control Store (WCS). Once this RAM is filled, a special switch write-protects it—effectively turning the RAM into ROM as long as the computer is turned on. The WCS cannot be corrupted by an errant application program or even a system crash.

The WCS was originally intended as a stopgap measure until the operating system could be firmed up and burned into ROM chips. But soon after the computer was introduced, Amiga recognized the value of an easily upgradable operating system and decided to stick with the WCS. One upgrade has already been released: The original version 1.0 was replaced with version 1.1 in late 1985. Version 1.1 added new features and cured legions of bugs that plagued 1.0, but it is still not perfect.

Over the past few months, Amiga has been working very hard to finish version 1.2. This upgrade was developed at first to work with the European Amiga, but includes numerous bug fixes and improvements as well. At this writing (mid-May), we have been exploring a prerelease version of 1.2, which might be available by the time you read this. Note that some features we'll describe may be changed in the final release version.

The most noticeable improvement in 1.2 is the much faster disk access due to a technique known as caching. A disk cache buffers disk reads so that frequently accessed areas of the disk are copied into RAM. From then on, the frequently accessed files are read from RAM rather than from the drive. It's similar to using the RAM disk, except that output is always stored on disk, not in RAM, so this technique is much safer than using a RAM disk. If the power is interrupted, you haven't lost your data.

Version 1.2 lets you choose how much memory to allocate for this disk cache—the more memory you set aside, the faster the disk access. The disk directory is also buffered, so directory-based operations such as Open requesters or an Amiga DOS DIR command work much faster. As a tradeoff, the momentary disk access that takes place when you first insert a disk lasts a little longer, since all directories and subdirectories are buffered. And, of course, there's less RAM available for applications, since the cache consumes some memory.

A Better Workbench

The Workbench is improved, too. The horizontal lines in a window's title bar have been thickened to reduce flickering in the interlaced modes. When entering text into a text gadget, you can reposition the cursor by pointing and clicking the mouse. You can use Left Amiga-V and -B as shortcuts for the affirmative and negative choices in a two-button requester. When you drag icons, you move an actual copy of the icon rather than a crossed circle. This even works with multiple selections, and is really impressive when you are dragging dozens of icons. Opening a Workbench window is no longer an excuse for a coffee break: Icons now pop up quickly, with little disk access. Any reference to the RAM: device creates an icon for the RAM disk on the Workbench screen, especially handy for one-drive systems.

A new Preferences tool lets you select serial port parameters such as data bits, stop bits, and so on, greatly simplifying the use of a serial printer or modem. There's also a toggle switch for Workbench Interlace On/Off. When Interlace is turned on, the Workbench changes to a 400-line screen with twice the vertical resolution, giving 50 lines of text.

There is a new Notepad on the Workbench disk, enhanced with an Edit menu permitting copy/cut/ paste and search-and-replace. You can set up the Notepad so it calls up only one font when loaded, then bring in the fonts later from a menu if you wish. You can select either character wrap or word-wrap, and you can intermix various fonts and styles in the same note. Scroll bars let you move quickly through your text. The Notepad is now almost a complete word processor.

All in all, the new operating system is very exciting. It almost makes the Amiga a whole different machine: faster, smoother, and more reliable than ever.