The Amiga 500 , so known under the name A500 , was the first model of line entry of the range Amiga 16 bits of Commodore International. It left in 1987, at the same time as the top-of-the-range model Amiga 2000, in direct competition with the Atari 520ST.
Description
A500 used the processor Motorola 68000, given rhythm with 7,14 MHz (STAKE) or 7,09 MHz (NTSC).Out of standard, the memory was of 512 KB, however, most of the users had increased it to 1 Mo of ChipRam. Possibilities of higher extensions of memory were offered by RAM known as FastRam.
The chip Agnus, initially able to address only 512 KB of ChipRam, then Fat Agnus managed the random access memory.
The chip Denise managed posting, with modes of going screen of 320x256 pixels (out of STAKE, 200 in NTSC) to 640x512 pixels (400 in NTSC). Thirty two simultaneous colors out of 4096 were displayable in mode 320, and sixteen in mode 640. However, the flexibility of the chipsets made very easy the use of two special modes, the mode “Halfbright” (“semitones” in French, though this term never was used by the Amiga community) and the mode “HAM-6” of 4096 simultaneous colors (12 bits), with constraints of proximity.
The chip Paula managed the sound on four ways. These ways being however accessible by DMA, and one did not have to the programmers a long time to exceed these limits, and to use only samples read directly in memory by Paula for the music.
A Disk drive standard double face/simple density of 3,5 inches (3.5") and was delivered, several could be connected into external, series. The reader had the characteristic to be completely controllable. Indeed Amiga could format diskettes in a completely free way, the basic format of the diskettes under AmigaDOS being of 880 KB, illegible on PC. Via a software like Crossdos, it was possible however to read diskettes doubles face/simple density coming from a PC, and formatted by this same PC.
Two ports DB-9 for joysticks, mouse and light pen were included:
- a Port series RS-232 standard of 25 contacts and
- a parallel Port Centronics of 25 contacts.
Technical specifications
-
Motorola 68000 (Microprocessor 32 bits CISC with 16 Register S without DRIVEN for the Protection memory and the virtual Memory)
- Operating system by defect: AmigaOS 1.2 or 1.3 (having a préemptif core Multi-task 32 bits) according to the revision
- 512 KB of Chip RAM by default (sound, graphic and software memory being in the same memory capacities)
- high limit of 16 Mo of memory, due to the limitations of the MC68000 (addressing report on 24 bits)
- chipset OCS
- left TV 50 Hz (STAKE) and 60 Hz (NTSC) by defect according to the versions. Mode 50/60 Hz rocking logiciellement in the revisions following
- filter passes low audio basculable logiciellement (the diode of the food dropping of intensity when the filter is extinct)
- division IRQ (as the Bus NCV)
- the system of IRQ had 7 levels of priority of interruptions
- not of limit in the number of peripheral interruptions
- managed by Autoconfig, very similar to ACPI. The peripherals were not counted or named, they gave just the size and the addresses which they needed.
See too
- List of plays Amiga
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