Editing Amiga 500 (section)

== Technical specifications ==
[[File:Amiga 1.3 and disks.jpg|thumb|right|The standard Amiga 500 requires floppies to boot.]]

* [[Original Amiga chipset|OCS]] (1.2 and 1.3 models) or [[Amiga Enhanced Chip Set|ECS]] (1.3 and 500+ 2.04 models) chipset. ECS revisions of the chipset made [[PAL]]/[[NTSC]] mode switchable in software.
** Sound: 4 hardware-mixed channels of 8-bit sound at up to {{nowrap|28 kHz}}.<ref>{{cite web |title=Amiga 500 |website=www.old-computers.com |url=http://www.old-computers.com/MUSEUM/computer.asp?c=65&st=1 |access-date=December 15, 2009 |archive-url=https://web.archive.org/web/20100330022140/http://www.old-computers.com/MUSEUM/computer.asp?st=1&c=65| archive-date=March 30, 2010 }}</ref> The hardware channels have independent volumes (65 levels) and sampling rates, and are mixed down to two fully left and fully right stereo outputs. A software controllable low-pass audio filter is also included.
* 512&nbsp;KB{{efn|name=binpre}} of chip RAM (150&nbsp;ns access time)
* [[AmigaOS]] 1.2 or 1.3 (upgradeable up to 3.1.4<ref>{{cite web |title=AmigaOS 3.1.4 on A500 |website=amigax1000.blogspot.com |date=December 15, 2018 |url=http://amigax1000.blogspot.com/2018/12/amigaos-314-on-a500.html |access-date=September 3, 2019 |archive-date=July 26, 2019 |archive-url=https://web.archive.org/web/20190726090428/http://amigax1000.blogspot.com/2018/12/amigaos-314-on-a500.html |url-status=live }}</ref> if 2&nbsp;MB{{efn|name=binpre}} of RAM are installed)
* One 3.5" double-density [[floppy disk drive]] is built in, which is completely programmable and thus can read {{nowrap|720 KB}} [[IBM PC]] disks, {{nowrap|880 KB}} standard Amiga disks, and up to {{nowrap|984 KB}} with custom formatting (such as Klaus Deppich's diskspare.device). Uses {{nowrap|300 rpm}} (5 rotations/second) and {{nowrap|250 kbit/s}}.
* Built-in keyboard
* A two-button mouse is included.

=== Graphics ===
* [[PAL]] mode: 768×580 maximum ([[overscan]] [[Interlaced video|interlaced]] if viewed on [[composite monitor]]/TV).<ref>{{Cite web |date=1990 |title=NewTek DigiView Gold Advert |url=http://amiga.resource.cx/adcoll/adcoll.pl?id=digiviewgold&pg=9 |access-date=2023-04-12 |website=Amiga Hardware Database |archive-date=January 28, 2023 |archive-url=https://web.archive.org/web/20230128095808/http://amiga.resource.cx/adcoll/adcoll.pl?id=digiviewgold&pg=9 |url-status=live }}</ref> Typical resolutions: 320×256, 640×256 or 640×512 (all displayed with borders).<ref name="amiga.lychesis.net">{{Cite web |title=Amiga Graphics Archive – Amiga Graphics Archive |url=http://amiga.lychesis.net/knowledge/ScreenModes.html |access-date=September 24, 2016 |archive-date=September 27, 2016 |archive-url=https://web.archive.org/web/20160927032905/http://amiga.lychesis.net/knowledge/ScreenModes.html |url-status=live }}</ref> 
* [[NTSC]] mode: 768×484 maximum (overscan interlaced if viewed on composite monitor/TV).<ref>{{Cite web |date=1989 |title=NewTek DigiView Gold advert |url=http://amiga.resource.cx/adcoll/adcoll.pl?id=digiviewgold&pg=5 |access-date=2023-04-12 |website=Amiga Hardware Database |archive-date=January 28, 2023 |archive-url=https://web.archive.org/web/20230128091703/http://amiga.resource.cx/adcoll/adcoll.pl?id=digiviewgold&pg=5 |url-status=live }}</ref> Typical resolutions: 320×200, 640×200 or 640×400 (all displayed with borders).<ref name="amiga.lychesis.net" /> 
* Graphics can be of arbitrary dimensions, resolution and colour depth, even on the same screen. The Amiga can show multiple resolution modes at the same time, splitting the screen vertically.
* [[Planar (computer graphics)|Planar]] graphics are used, with up to five bitplanes (four in hires); this allowed 2, 4, 8, 16 and 32 colour screens, from a palette of 4096 colours. 
* Two special graphics modes are also included: 
** [[Amiga Halfbrite mode|Extra Half Brite]] (EHB), which uses a sixth bitplane as a mask that halved the brightness of any colour seen
** [[Hold-And-Modify]] (HAM), which allows all 4096 colours on screen at once. HAM makes it possible to use {{nowrap|12 bpp}} over a {{nowrap|3 [[pixel]]}} wide span. This works by letting each pixel position use the previous RGB value and modify one of the red, green or blue values to a new 4-bit value. This will cause some negligible colour artifacts however.

=== Memory ===
Using various expansion techniques, the A500's total RAM can reach up to 138&nbsp;MB – 2&nbsp;MB Chip RAM, 8&nbsp;MB 16-bit Fast RAM, and 128&nbsp;MB 32-bit Fast RAM.{{efn|name=binpre}}

==== Chip RAM ====
The stock 512&nbsp;KB Chip RAM can be complemented by 512&nbsp;KB using a "trapdoor" expansion (Commodore A501 or compatible).{{efn|name=binpre}} While that expansion memory is connected to the chip bus, hardware limitations of early stock Agnus chip revisions prevent its use as Chip RAM, only the CPU can access it. Suffering from the same contention limitations as Chip RAM, that memory is known as "Slow RAM" or "Pseudo-fast RAM". Agnus revisions shipped with late A500 are [[Amiga Enhanced Chip Set|ECS]] and allow use of trapdoor RAM as real Chip RAM for a total 1&nbsp;MB.{{efn|name=binpre}} 

Additionally, several third-party expansions exist with up to 2&nbsp;MB{{efn|name=binpre}} on the trapdoor board. Using a [[Amiga custom chips#Gary|Gary]] adapter, that memory will be mapped as either split on Chip RAM and Slow RAM or fully as Slow RAM, depending on configuration.

Furthermore, using an [[Amiga 3000|A3000]] Agnus on an adapter board, it is possible to expand the Chip RAM to 2&nbsp;MB, matching the A500+.{{efn|name=binpre}}

==== Fast RAM ====
"Fast" RAM is located on the CPU-side bus. Its access is exclusive to the CPU and not slowed by any chipset access. The side expansion port allows for up to 8&nbsp;MB{{efn|name=binpre}} of [[Zorro II|Zorro-style]] expansion RAM. Alternatively, a CPU adapter allows for internal expansion.

==== Accelerator RAM ====
Internal or external CPU accelerators often include their own expansion memory. 16-bit CPUs are limited by the 24-bit address space but they can repurpose otherwise unused memory space for their included RAM. 32-bit CPU accelerators aren't limited by 24-bit addressing and can include up to 128&nbsp;MB{{efn|name=binpre}} of Fast RAM (and potentially more).

==== Memory map ====
{| class="wikitable"
|+Amiga system memory map{{Sfn|Greenley|Green|Baker|1991|p=314}}<ref>{{cite web | url=http://oscomp.hu/depot/amiga_memory_map.html | title=Amiga memory map | access-date=August 12, 2023 | archive-date=August 12, 2023 | archive-url=https://web.archive.org/web/20230812110419/http://oscomp.hu/depot/amiga_memory_map.html | url-status=live }}</ref>
|-
! Address    || Size in KB{{efn|name=binpre}} || Description
|-
|align="right"| 0x00 0000 <!--0x0003FFFF-->
|align="right"| 256 || Chip RAM
|-
|align="right"| 0x04 0000 <!--0x0007FFFF-->
|align="right"| 256 || Chip RAM ([[Amiga 1000|A1000]] option card)
|-
|align="right"| 0x08 0000 <!--0x000FFFFF-->
|align="right"| 512 || Chip RAM expansion
|-
|align="right"| 0x10 0000 <!--0x001FFFFF-->
|align="right"| 1024 || Extended Chip RAM for [[Amiga Enhanced Chip Set|ECS]]/[[Amiga Advanced Graphics Architecture|AGA]]
|-
|align="right"| 0x20 0000 <!--0x009FFFFF-->
|align="right"| 8192 || Primary auto-config space (Fast RAM)
|-
|align="right"| 0xA0 0000 <!--0x00BEFFFF-->
|align="right"| 1984 || Reserved
|-
|align="right"| 0xBF D000 <!--0x00BFDF00-->
|align="right"| 3.8 || [[MOS Technology CIA|8520-B]] (even-byte addresses)
|-
|align="right"| 0xBF E001 <!--0x00BFEF01-->
|align="right"| 3.8 || 8520-A (odd-byte addresses)
|-
|align="right"| 0xC0 0000 <!--0x00D7FFFF-->
|align="right"| 1536 || Internal expansion memory (pseudo-fast, "slow" RAM on Amiga 500)
|-
|align="right"| 0xD8 0000 <!--0x00DBFFFF-->
|align="right"| 256 || Reserved
|-
|align="right"| 0xDC 0000 <!--0x00DCFFFF-->
|align="right"| 64 || [[Real-time clock|Real time clock]]
|-
|align="right"| 0xDD 0000 <!--0x00DFEFFF-->
|align="right"| 188 || Reserved
|-
|align="right"| 0xDF F000 <!--0x00DFFFFF-->
|align="right"| 4 || Custom chip registers
|-
|align="right"| 0xE0 0000 <!--0x00E7FFFF-->
|align="right"| 512 || Reserved
|-
|align="right"| 0xE8 0000 <!--0x00E8FFFF-->
|align="right"| 64 || [[Amiga Zorro II|Zorro II]] auto-config space (before relocation)
|-
|align="right"| 0xE9 0000 <!--0x00EFFFFF-->
|align="right"| 448 || Secondary auto-config space (usually 64K I/O boards)
|-
|align="right"| 0xF0 0000 <!--0x00F7FFFF-->
|align="right"| 512 || 512K System ROM (reserved for extended ROM image e.g. CDTV or CD<sup>32</sup>)
|-
|align="right"| 0xF8 0000 <!--0x00FBFFFF-->
|align="right"| 256 || 256K System ROM ([[Kickstart (Amiga)|Kickstart]] 2.04 or higher)<!-- According to the linked wikipage, contradicts "ntrautanen_fi-amiga_memory" -->
|-
|align="right"| 0xFC 0000 <!--0x00FFFFFF-->
|align="right"| 256 || 256K System ROM
|}

=== Connectors ===
[[File:AMIGA500-3.jpg|thumb|290px|Backside of the base of the Amiga 500. From left to right, it features two [[Atari joystick port]]s, two audio connectors, a floppy drive port, a serial and a parallel port, a power input, and two separate inputs for RGB and monochrome monitors.{{Sfn|Introduction to the Amiga 500|1987|p=2-1}}]]
[[File:Amiga_520_1.jpg|thumb|right|The Amiga 520 adapter allows for an [[RF modulator|RF modulated]] output to be connected to a TV, or composite output to a monitor.]]

* Two [[Atari joystick port]]s for [[joystick]]s or [[Mouse (computing)|mice]]
* Stereo audio [[RCA connector]]s ({{val|1|u=V}} [[Peak-to-peak|p-p]])
* A floppy drive port (DB23F), for daisy-chaining up to 3 extra floppy disk drives via a [[D-subminiature|DB23F]] connector<ref name="gbwxgm"/>
* A standard [[RS-232]] serial port (DB25M)
* A [[parallel port]] (DB25F)
* Power inlet ({{val|+5 |u=V}}, {{val|p=±|12 |u=V}})<ref name = "itgehi" />
* [[Amiga video connector]]: Analogue [[RGB color model|RGB]] {{val|50|ul=Hz}} PAL and {{val|60 |u=Hz}} NTSC video output, provided on an Amiga-specific [[DB23]]M connector. Can drive video with {{val|15.75 |u=kHz}} [[Horizontal sync|HSync]] for standard Amiga video modes. This is not compatible with most [[Video Graphics Array|VGA]] monitors. A [[Multisync monitor]] is required for some higher resolutions. This connection can also be [[genlock]]ed to an external video signal. An [[RF modulator|RF adapter]] (A520) was frequently bundled with the machine to provide output on regular televisions or on [[composite video|composite]] monitors. A digital 16 colour Red-Green-Blue-Intensity signal is available too on the same connector.
* Monochrome video via an [[RCA connector]]
* [[Zorro II]] bus expansion on the left side behind a plastic cover
* Trapdoor slot under the machine, for RAM expansion and [[real-time clock]]

=== Expansions ===
* Expansion ports are limited to a side expansion port and a trapdoor expansion on the underside of the machine. The casing can also be opened up (voiding the warranty), all larger chips are socketed rather than being [[Through-hole technology|TH]]/[[Surface Mount Device|SMD]] soldered directly to the motherboard, so they can be replaced by hand.
* The CPU can be upgraded to a Motorola 68010 directly or to a 68020, 68030 or 68040 via the side expansion slot or a CPU socket adapter board.
* The chip RAM can be upgraded to {{nowrap|1 MB}}{{efn|name=binpre}} directly on the motherboard, provided a [[Fat Agnus]] chip is also installed to support it.
* Likewise, all the custom chips can be upgraded to the [[Extended chip set|ECS]] chipset.
* The A500+ model instead allowed upgrading by {{nowrap|1 MB}}{{efn|name=binpre}} trapdoor chip RAM without clock, but there was no visible means on board to map any of this as FAST, causing incompatibility with some stubbornly coded programs.
* There were modification instructions available for the A500 to solder or socket another {{nowrap|512 KB}} RAM on the board, then run extra address lines to the trapdoor slot to accommodate an additional {{nowrap|1 MB}} of fast or chip RAM depending on the installed chipset.{{efn|name=binpre}}
* Up to {{nowrap|8 MB}}{{efn|name=binpre}} of "fast RAM" can be added via the side expansion slot, even more if an [[Hardware acceleration|accelerator]] with a non-EC (without reduced data/address bus) processor and 32-bit RAM is used.
* Hard drive and other peripherals can be added via the side expansion slot.
* Several companies provided combined CPU, memory and hard drive upgrades{{snd}}or provided chainable expansions that extended the bus as they were added{{snd}}as there is only one side expansion slot.
* Expansions are configured automatically by [[AutoConfig]] software, so multiple pieces of hardware did not conflict with each other.

===Diagnostics===
When the computer is powered on a self-diagnostic test is run that will indicates failure with a specific colour:

#{{background color|#00B300|&nbsp;&nbsp;}} Medium green means chip RAM is not found or is damaged.
#{{background color|darkred|&nbsp;&nbsp;}} Red means bad [[Kickstart (Amiga)|kickstart]]-[[Read-only memory|ROM]].
#{{background color|yellow|&nbsp;&nbsp;}} Yellow means the [[central processing unit|CPU]] has crashed (no trap routine or trying to run bad code) or a bad [[Amiga Zorro II|Zorro]] [[expansion card]].<ref>[http://eab.abime.net/showthread.php?t=497 abime.net – Question blinking power LED/no screen on Amiga 500] read November 3, 2011</ref>
#{{background color|blue|&nbsp;&nbsp;}} Blue means a custom chip problem ([[Denise (OCS)|Denise]], [[Paula (computer chip)|Paula]], or [[Original Chip Set#Agnus|Agnus]]).
#{{background color|lime|&nbsp;&nbsp;}} Light green means [[MOS Technology CIA|CIA]] problem.
#{{background color|silver|&nbsp;&nbsp;}} Light gray means that the CIA might be defective.
#{{nowrap|{{background color|black|&nbsp;}} {{background color|black|&nbsp;}} Black and white stripes}}<!--verify?--> mean there is a ROM or [[MOS Technology CIA|CIA]] problem.
#{{background color|black|&nbsp;&nbsp;}} Black-only (no video) means there is no video output.<ref name=a3b>[http://amiga.serveftp.net/A3000_HardwareGuide/booting-problems.html amiga.serveftp.net – A3000 Booting Problems] {{Webarchive|url=https://web.archive.org/web/20120425132759/http://amiga.serveftp.net/A3000_HardwareGuide/booting-problems.html |date=April 25, 2012 }} read November 3, 2011</ref>

The keyboard [[light-emitting diode|LED]] uses blink codes:

#One blink means the keyboard ROM has a checksum error.
#Two blinks means RAM failure.
#Three blinks means watchdog timer failure.<ref name=a3b/>
'''<big>Measurements</big>'''

Overall (base): 6.2 cm x 47.4 cm x 33 cm; 2 7/16 in x 18 11/16 in x 13 in. <ref>{{Cite web |title=Commodore Amiga 500 Personal Computer |url=https://americanhistory.si.edu/collections/search/object/nmah_834010 |access-date=2023-09-27 |website=National Museum of American History |language=en |archive-date=September 12, 2023 |archive-url=https://web.archive.org/web/20230912221548/https://americanhistory.si.edu/collections/search/object/nmah_834010 |url-status=live }}</ref>