Editing Commodore SX-64 (section)

== Description ==
Aside from its built-in features and different form factor, there are several other differences between the SX-64 and the regular C64. The default screen color is changed to blue text on a white background for improved readability on the smaller screen. This can cause compatibility problems with programs that assume the C64's default blue background. <!-- (This is, however, often easily overcome by the user simply entering the appropriate [[BASIC]] [[PEEK and POKE|POKE]] commands to change screen colors and keystroke to change the cursor color to mimic the C64's default colors prior to loading of the program.)--> The default device for load and save operations is changed to the floppy drive.

The Datasette (cassette) port and [[RF modulator|RF]] port were omitted from the SX-64. Because it has a built-in disk drive and monitor, Commodore did not perceive a need for a [[tape drive]] or television connector. However, the lack of a Datasette port poses a problem for a number of C64 [[Centronics]] parallel printer interfaces, since several popular designs "borrowed" their +5V power supply from the port. This was not an issue for later interfaces which were supplied with an AC adapter power supply, or those which can use the +5V line supplied by the Centronics port (Pin #18) on the printer itself, if the printer implements it. Alternatively, a +5V supply is also available from the joystick ports.

The audio/video port is still present, so an external monitor can still be used;<ref name="benford198502">{{cite news|url=https://archive.org/stream/Ahoy_Issue_14_1985-02_Ion_International_US#page/n35/mode/2up|title=SX-64 Portable Computer|author=Benford, Tom|date=February 1, 1985|work=Ahoy!|access-date=October 15, 2013|pages=37–38}}</ref> it displays the same content as the built-in monitor.<ref name="cc19850121">{{cite episode | title=Ghostbusters demo | series=The Computer Chronicles | credits=Crane, David | network=PBS | url=https://www.youtube.com/watch?v=95L0gRRxs6k  |archive-url=https://ghostarchive.org/varchive/youtube/20211221/95L0gRRxs6k |archive-date=2021-12-21 |url-status=live| airdate=1985-01-21}}{{cbignore}}</ref> Differences, electrically and in placement on the board, means that there are compatibility problems with some C64 cartridges.

The original SX-64's (built in) power supply limits the machine's expandability.{{citation needed|date=October 2013}}

Compatibility with Commodore [[Commodore REU|RAM Expansion Unit]]s varies. Early SX-64 power supplies cannot handle the extra power consumption from the REU. The physical placement of the cartridge port can prevent the REU from seating properly. The 1700 and 1750, 128K and 512K units intended for the [[Commodore 128|C128]], are said to work more reliably with the SX-64 than the 1764 unit that was intended for the regular C64. Some SX-64 owners modify Commodore REUs to use an external power supply in order to get around the power supply issues.
IDE64 is also non-compatible at the present time. When it is powered up, the screen sends out the C64 breadbin "blue" background with the typical <code>38911 BASIC BYTES FREE</code>, and immediately under the <code>READY</code> prompt a statement of <code>RAM</code> is displayed.

A version of the SX-64 with dual floppy drives, known as the '''DX-64''', was announced, but the press reported by early 1985 that plans for its release had been suspended.{{r|benford198502}} A few have been reported to exist {{By whom|date=December 2017}}, but it is very rare. Instead of an extra floppy drive, a modem could also be built in above the first drive. Some hobbyists installed a second floppy drive themselves in the SX-64's empty drive slot.  Later models of the SX-64 use the larger power supply intended for use with the DX-64.

At around the same time the SX-64 was announced in January 1983, a version with a monochrome screen called the '''SX-100''' was announced. Despite releasing plans by June 1983, it was never released.