Editing Commodore 64 (section)

=== {{anchor|Hardware revisions}}Revisions ===
[[File:3 versioner av c64 (modified).jpg|thumb|upright=1.2|Three case styles were used: C64 (top, 1982), C64C (middle, 1986) and C64G (bottom, 1987).]]
Commodore made many changes to the C64's hardware, sometimes introducing compatibility issues.<ref name="halfhill198307">{{cite news | url=https://archive.org/stream/1983-07-computegazette/Compute_Gazette_Issue_01_1983_Jul#page/n41/mode/2up | title=Commodore 64 Video Update | work=Compute!'s Gazette | date=July 1983 | access-date=February 6, 2016 | last=Halfhill | first=Tom R. | page=40}}</ref> The computer's rapid development and Commodore and [[Jack Tramiel]]'s focus on cost-cutting instead of product testing resulted in several defects which caused developers like Epyx to complain and required many revisions; Charpentier said that "not coming a little close to quality" was one of the company's mistakes.{{r|ieee85}}

Cost reduction was the reason for most of the revisions. Reducing [[manufacturing cost]]s was vitally important to Commodore's survival during the [[price war]] and lean years of the 16-bit era. The C64's original ([[NMOS logic|NMOS]]-based) motherboard went through two major redesigns and a number of revisions, exchanging positions of the VIC-II, SID and [[programmable logic array|PLA]] chips. Much of the cost was initially eliminated by reducing the number of discrete components, such as [[diode]]s and [[resistor]]s, which enabled a smaller [[printed circuit board]]. There were 16 C64 motherboard revisions to simplify production and reduce manufacturing costs. Some board revisions were exclusive to [[PAL region]]s. All C64 motherboards were manufactured in [[Hong Kong]].

IC locations changed frequently with each motherboard revision, as did the presence (or lack) of the metal RF shield around the VIC-II; PAL boards often had aluminized cardboard instead of a metal shield. The SID and VIC-II are socketed on all boards, but the other ICs may be socketed or soldered. The first production C64s, made from 1982 to early 1983, are known as "silver label" models due to the case having a silver-colored "Commodore" logo. The power LED had a silver badge reading "64" around it. These machines have only a five-pin video cable, and cannot produce [[S-Video]]. Commodore introduced the familiar "rainbow badge" case in late 1982, but many machines produced into early 1983 also used silver-label cases until the existing stock was used up. The original 326298 board was replaced in spring 1983 by the 250407 motherboard, which had an eight-pin video connector and added S-Video support. This case design was used until the C64C appeared in 1986. All ICs switched to plastic shells, but the silver-label C64s (notably the VIC-II) had some ceramic ICs. The case is made from [[Acrylonitrile butadiene styrene|ABS]] plastic, which may become brown with time; this can be reversed with [[retrobright]].

==== ICs ====
[[File:C64motherboard.jpg|thumb|right|upright=1.6|alt=See caption|An early C64 motherboard (Rev A [[PAL]] 1982)]]
[[File:C64Cmotherboard.jpg|thumb|right|upright=1.6|alt=See caption|A C64C motherboard ("C64E" Rev B PAL 1992)]]
The VIC-II was manufactured with 5-[[micrometre|micrometer]] NMOS technology{{r|ieee85}}, and was clocked at {{nowrap|17.73447 MHz}} (PAL) or {{nowrap|14.31818 MHz}} (NTSC). Internally, the clock was divided to generate the dot clock (about 8&nbsp;MHz) and the [[two-phase clock|two-phase system clocks]] (about 1&nbsp;MHz; the pixel and system clock speeds differ slightly on NTSC and PAL machines). At such high clock rates the chip generated considerable heat, forcing MOS Technology to use a ceramic [[dual in-line package]] known as a CERDIP. The ceramic package was more expensive, but dissipated heat more effectively than plastic.

After a redesign in 1983, the VIC-II was encased in a plastic dual in-line package; this reduced costs substantially, but did not eliminate the heat problem.{{r|ieee85}} Without a ceramic package, the VIC-II required a [[heat sink]]. To avoid extra cost, the metal [[radio frequency|RF]] [[electromagnetic shielding|shielding]] doubled as the VIC's heat sink; not all units shipped with this type of shielding, however. Most C64s in [[Europe]] shipped with a cardboard [[Electromagnetic shielding|RF shield]] coated with a layer of metal foil. The effectiveness of the cardboard was questionable; it acted instead as an insulator, blocking airflow and trapping heat generated by the SID, VIC, and PLA chips. The SID was originally manufactured using NMOS at 7 micrometers and, in some areas, 6 micrometers.{{r|ieee85}} The prototype SID and some early production models had a ceramic dual in-line package, but (unlike the VIC-II) are very rare; the SID was encased in plastic when production began in early 1982.

==== Motherboard ====
In 1986, Commodore released the last revision of the classic C64 [[motherboard]]. It was otherwise identical to the 1984 design, except for two 64-[[kilobit]] × 4-bit [[DRAM]] chips which replaced the original eight 64-kilobit × 1-bit ICs. After the release of the Commodore 64C,<ref name='Commodore 64c abbreviated as "C64C" (capital c on both ends)'>{{cite web|last1=Kirk|first1=Mandy|title=Commodore 64C System Guide at Auction on ebay|url=http://www.ebay.com/itm/Commodore-64C-Personal-Computer-System-Programming-Guide-Manual-RARE-/321552326540?pt=US_Vintage_Computing_Manuals_Merchandise&hash=item4ade031f8c|website=www.ebay.com|publisher=Commodore International|access-date=October 17, 2014}}</ref> MOS Technology began to reconfigure the original C64's [[chipset]] to use [[HMOS]] technology. The main benefit of HMOS was that it required less voltage to drive the IC, generating less heat. This enhanced the reliability of the SID and VIC-II. The new chipset was renumbered 85xx to reflect the change to HMOS.

In 1987, Commodore released a 64C variant with a redesigned motherboard known as a "short board". The new board used the HMOS chipset, with a new 64-pin PLA chip. The "SuperPLA", as it was called, integrated discrete components and [[transistor–transistor logic]] (TTL) chips. In the last revision of the 64C motherboard, the 2114 4-bit-wide color RAM was integrated into the SuperPLA.