Editing Tandy 2000 (section)

=== Graphics ===
The base-model Tandy 2000 supported only a text-mode display in monochrome.<ref name=":0">{{Cite news |last=JENNINGS |first=MARK S. |date=December 1984 |title=SYSTEM RE VIEW - The Tandy Model 2000 |url=https://www.tech-insider.org/personal-computers/research/acrobat/8412-b.pdf |work=BYTE |pages=239 - 248}}</ref> The Tandy VM-1 monitor used the 8-pin [[DIN connector|DIN]] video port on the computer's rear panel. The text-mode address space was in a different location but third-party memory-resident software hacks remedied this by copying the PC-compatible text-mode memory to the Tandy 2000's text space at a rate of 5–10 times per second. This sometimes caused some choppiness in the display. It produced a fast text display rate—often too fast to read—but the 'HOLD' key on the keyboard could be used to pause text output.

The bit pattern for each text character's raster image was maintained in RAM and could be modified by the user. With clever programming the display's ability to present fine lines provided by the 640x400 screen resolution could be accessed in text mode even without the optional graphics board.

==== Tandy 2000 Graphics Adapter ====
[[File:Tandy 2000 Color Graphics Option 640x400x8 ar corrected.png|thumb|Tandy 2000 Color Graphics Option 640 × 400 x 8 colors]]
The display was upgradable to support pixel-addressable graphics via the Tandy 2000 Graphics Adapter, a circuit board that fit into an expansion slot.<ref name=":0" /> It had its own connector for the monochrome VM-1 monitor; the video connector in the rear-panel cabinet was disabled when this expansion board was installed. The graphics resolution was 640x400 and supported high intensity pixels.

Color capability was provided by the Color Graphics Option,<ref name=":0" /> which was a set of chips that were inserted into the empty sockets on the monochrome Graphics Adapter provided for this purpose.<ref group="note">The Color chipset comprises 16 readily-available chips: eight 4416-15 DRAMs, four 74F245s, and four 25LS22 chips. A trace cut on the graphics board was also required.</ref><ref>{{cite web|title=Model 2000 Color Graphics Option Kit Installation Instructions|url=http://www.classiccmp.org/cini/pdf/Tandy/Tandy%202000%20Color%20Chip%20Kit%20Install%20Manual.pdf|website=ClassicCMP|accessdate=May 23, 2016}}</ref> Resolution for the color board was the same 640x400, non-interlaced, and eight colors out of a palette of sixteen available colors were displayable on the Tandy CM-1 monitor (~$799).<ref name=":0" /> This was a particularly high-resolution and colorful display for its day. The CM-1 monitor accepted, as input from the color graphics board, [[List of monochrome and RGB color formats#4-bit RGBI|digital RGBI signals]] (indicating separate Red, Green, and Blue signals with a Intensity bit).<ref name=":1">{{Cite book |url=https://github.com/Tandy2K/Tandy2000/blob/master/Hardware/Technical%20Reference%2026-5404.pdf |title=Tandy Model 2000 Technical Reference Manual |date=1984 |publisher=Tandy Corporation |publication-date= |pages=278}}</ref> [[Color Graphics Adapter|CGA]] compatibility was hit-or-miss.
{| class="wikitable sortable"
|+Tandy 2000 Graphics Adapter Color Graphics Option hardware palette on CM-1 monitor <ref name=":1" />
!Color
!I
!R
!G
!B
!Color
!I
!R
!G
!B
|-
|Black
|0
|0
|0
|0
|Black
|1
|0
|0
|0
|-
|Dark Blue
|0
|0
|0
|1
|Blue
|1
|0
|0
|1
|-
|Dark Green
|0
|0
|1
|0
|Green
|1
|0
|1
|0
|-
|Dark Cyan
|0
|0
|1
|1
|Cyan
|1
|0
|1
|1
|-
|Dark Red
|0
|1
|0
|0
|Red
|1
|1
|0
|0
|-
|Dark Magenta
|0
|1
|0
|1
|Magenta
|1
|1
|0
|1
|-
|Dark Yellow
|0
|1
|1
|0
|Yellow
|1
|1
|1
|0
|-
|Gray
|0
|1
|1
|1
|White
|1
|1
|1
|1
|}
There were only three non-Tandy monitors that worked with the Tandy 2000 graphics card, all of which are long out of production. These were the original (1986–88) Mitsubishi Diamond Scan, and the [[NEC]] Multisync and Multisync GS (grayscale).<ref>{{cite web|title=Tandy 2000 FAQ|url=http://www.classiccmp.org/cini/docs/t2kfaq.txt|website=Classiccmp.org|publisher=Classic Computer, Jeff Hellige|accessdate=May 23, 2016}}</ref> The required horizontal scan frequency for the Tandy 2000 is 26.4&nbsp;kHz. Modern flat-panel multisync computer monitors cannot sync at frequencies below 30&nbsp;kHz. The CM-1 monitor is also digital RGB; all modern CRT monitors are analog-only.