The Megamidget Racer 68030 Accelerator
by Chris Zamara
lega-WSii terek Grime tell out of commands.
ou might not guess from its oxymoron of a name, but the Mega-Midget Racer from Computer System Associates (CSA) is a 68030/FPU accelerator board for the Amiga 500. 1000, or 2000. The board plugs into the MC68000 CPU socket and fits neatly inside the computer's case. There are several accelerator boards to choose from for the Amiga, but the Mega-Midget Racer (MMR) is. comparatively speaking, inexpensive: the 20 MHz version of the basic board is $795, which translates to big numbers on the bang-for-the-buck scale.
An accelerator board might seem like an unnecessary luxury for your computer until you try one on; the added performance of the machine can change its whole personality. An accelerated machine feels different from the stock machine for much the same reason driving a high-performance sports car feels different from driving an econobox: speed and power. For most applications, the extra speed makes things seem more effortless: requesters pop up right now, text conversions or spreadsheet recalculations seem instant, text appears on the display without looking like it was rendered one line at a time. With a math coprocessor chip installed, the effect can be even more dramatic: raytracing. Mandelbrot generation, or other calculations involving floating-point math can benefit enormously. One of the Mandelbrot benchmark tests provided with the CSA board shows a speed increase of more than 50 times over a standard Amiga 2000!
How Accelerators Accelerate
A basic reason for the performance increase is the use of a MC68030 CPU instead of the standard MC68000. The 68030. with its improved instruction pipelining and instruction cache, churns through code faster than a 68000, even at an equiva lent clock frequency (the clock frequency determines the length of each CPU cycle, which dictates the speed at which the CPU runs). Coupled with a higher clock speed than usual - the standard Amiga's 68000 is clocked at 7 MHz (MegaHertz), while the 68030 on the accelerator board can run at speeds up to 33 MHz - the resulting performance increase affects almost every aspect of computing. As you can see in the bar chart on the next page, the 'Sieve' benchmark runs almost six times faster with a 25 MHz 68030 over the stock 7 MHz 68000.
Another source of added speed comes into play only when 32-bit memory expansion is used. Memory that can be addressed in 32-bit words takes advantage of the 68030's 32-bit address bus. allowing a 32-bit value to be loaded by a single memory fetch instead of two 16-bit fetches. The Mega-Midget Racer board has connectors for an optional 32-bit RAM daughterboard which can hold from one to eight megabytes of RAM. It also has on-board sockets for 512k of high-speed static RAM that can be used to store a copy of the Amiga's ROM operating system and execute ROM routines from there instead of from the slower 16-bit ROM (or RAM in the Amiga 1000) memory chips. The use of 32-bit RAM is responsible for a significant speed increase, and brings out the full potential of the accelerator board. As you can see in the yellow bars of the benchmark graphs, the use of the 32-bit DRAM increases performance substantially in most tests.
What a fast 68030 with 32-bit memory can do for everyday computing is nothing compared to what an FPU (Floating-Point Unit) coprocessor can do for floating-point math. The Mega-Midget Racer has a socket for the installation of a MC68881 or a MC68882 math coprocessor, which can be clocked at a different frequency from the 68030 by the installation of a separate crystal: depending on the coprocessor chip that
NEW ORDEjR LINE/
InterComputing, Inc. 1-800-800-9177
2112 Sandy Lane, Dallas, TX 75220 • Customer Service: 214-556-9666 • FAX: 214-556-2336
iBlerCoapvtmg Deutschland Inc.
Schönebecker Str. 55-57 Telefon: 0202/89155 5600 Wuppertal-2 Telefon: 0202/89304
InterComputing France
34, Avenue des Champs Elysees 75008 Paris
Phone:(l) 42821603
Post a comment