Editing MOS Technology VIC-II (section)

===The VIC-IIe===
[[Image:MOS 8566 VIC-IIe pinout.png|right|MOS 8566 VIC-IIe pinout]]
The 8564/8566 VIC-IIe in the [[Commodore 128]] uses 48 pins rather than 40, as it produces more signals, among them the clock for the additional [[Zilog Z80]] CPU of that computer. It also has two extra registers. One of the additional registers is for accessing the added numerical keypad and other extra keys of that computer; this function was added to the VIC merely because that proved to be the easiest place in the computer to add the necessary three extra output pins. The other extra register is for toggling between a 1&nbsp;MHz and a 2&nbsp;MHz system clock; at the higher speed the VIC-II's video output is merely displaying every second byte in the code as black hires bit-pattern on the screen, suggesting use of the C128's 80-column mode at that speed (via the [[MOS Technology 8563|8563 VDC]] RGB chip). Rather unofficially, the two extra registers are also available in the C128's C64 mode, permitting some use of the extra keys, as well as double-speed-no-video execution of [[CPU bound|CPU-bound]] code (such as intensive numerical calculations) in self-made C64 programs.<ref name="compute128">{{cite book
 | author1   = Cowper, Ottis R.
 | author2   = Florance, David
 | author3   = Heimarck, Todd D.
 | author4   = Krause, John
 | author5   = Miller, George W.
 | author6   = Mykytyn, Kevin
 | author7   = Nelson, Philip I.
 | author8   = Victor, Tim
 | title     = COMPUTE!'s 128 Programmer's Guide
 | date      = October 1985
 | publisher = [[Compute!|COMPUTE! Publications]]
 | location  = Greensboro, North Carolina
 | isbn      = 0-87455-031-9
 | pages     = 348&ndash;349
 | chapter   = Chapter 7. System Architecture}}</ref> The extra registers are also one source of minor incompatibility between the C128's C64 mode and a real C64 - a few older C64 programs inadvertently wrote into the {{val|2 |ul=MHz}} toggle bit, which would do nothing at all on a real C64, but would result in a messed-up display on a C128 in C64 mode.

The VIC-IIe has the little-known ability to create an additional set of colors by manipulating the registers in a specific way that puts the color signal out of phase with what other parts of the chip consider it to be in.{{Citation needed|date=March 2020}} This ability was demonstrated in the "Risen from Oblivion" demo. <ref>{{Cite web |title=Risen from Oblivion - trivia |url=https://csdb.dk/release/?id=2942&show=trivia#trivia}}</ref> Unfortunately it does not work on all monitors - correct colors are confirmed on Commodore CRT monitors and their equivalents.

Using the specific behavior of the VIC-IIe's test bit, it is furthermore capable of producing a real interlace picture with a resolution of 320×400 (hires mode) and 160×400 (multicolor mode).<ref>{{Cite web |title=VIC-IIe Interlace |url=https://sites.google.com/site/h2obsession/CBM/C128/Interlace}}</ref>