Editing TRS-80 (section)

=== Model 4{{anchor|model4}} ===
{{main|TRS-80 Model 4}}
[[File:TRS-80 Model 4 (modified).jpg|thumb|TRS-80 Model 4 (standard version)]]
[[File:TRS-80 Model 4P Crop Delsener.jpg|thumb|TRS-80 Model 4P]]
The successor to the Model III is the [[TRS-80 Model 4]] released in April 1983. It has a faster Z80A {{val|4|u=MHz}} CPU,<ref>{{cite web|url=http://www.trs-80.com/wordpress/trs-80-computer-line/model-4/ |title=TRS-80 Computers: TRS-80 Model 4 |publisher=Trs-80.com |date=March 4, 2009 |access-date=August 13, 2013}}</ref> a larger video display 80 columns x 24 rows with reverse video, bigger keyboard, internal speaker, and its 64 KB of RAM can be upgraded to 128 KB of [[bank switching|bank-switched]] RAM. The display can be upgraded with a high-resolution graphics card yielding 640{{resx}}240 pixels. The Model 4 is fully compatible with Model III and CP/M application software. A diskless Model 4 (with 16 KB RAM and Level II BASIC) cost {{US$|long=no|999}}, with 64 KB RAM and one single-sided 180K disk drive {{US$|long=no|1699}}, and two drives with RS-232C {{US$|long=no|1999}}; an upgrade for Model III owners cost {{US$|long=no|799}} and provided a new motherboard and keyboard.<ref name="archer198310">{{cite magazine |url=https://archive.org/stream/byte-magazine-1983-10/1983_10_BYTE_08-10_UNIX#page/n293/mode/2up |title=Radio Shack's TRS-80 Model 4 |magazine=[[Byte (magazine)|Byte]] |date=October 1983 |volume=8 |issue=10 |access-date=January 31, 2015 |author=Archer, Rowland Jr. |pages=292–302}}</ref> Tandy sold 71,000 in 1984.<ref name="bartimo19850311">{{cite magazine |last=Bartimo |first=Jim |date=March 11, 1985 |url=https://books.google.com/books?id=5C4EAAAAMBAJ&pg=PA28 |title=Tandy Revamps Product Line |magazine=[[InfoWorld]] |volume=7 |issue=10 |access-date=January 21, 2015 |pages=28–29}}</ref>

The Model 4 includes all of the Model III's hardware, port assignments, and operating modes, making it 100% compatible. Model III programs running on a Model 4 can access the Model 4's added hardware features (like 4&nbsp;MHz clock rate, bigger video screen and keyboard, banked RAM above 64 KB). There were aftermarket software packages that made this ability available to non-programmer users.<ref>{{cite web |last1=Soltoff |first1=Roy |title=The Misosys Quarterly Vol. I.iii pg. 6, "LDOS 5.3 Model 4 Hardware Interface Kit" |url=https://www.tim-mann.org/trs80/doc/TMQ%20Vol%20I.iii.pdf |website=tim-mann dot org |publisher=Misosys, Inc. |access-date=November 12, 2019}}</ref><ref>{{cite magazine |last1=Dalton |first1=David |magazine=[[80 Micro]] |page=33 |type=product review |title=The Enhancer |url=https://archive.org/details/80-microcomputing-magazine-1985-09/page/n33 |publisher=CW Communications |access-date=November 12, 2019 |date=September 1985}}</ref>

The Model 4P is a transportable version introduced in September 1983 and discontinued in early 1985. It is functionally the same as the dual-drive desktop model but lacks the card edge connector for two outboard diskette drives and for a cassette tape interface. It has a slot for an internal modem card and could emulate a Model III.

The Model 4D with bundled Deskmate productivity suite was introduced in early 1985. It has a revised CPU board using faster gate array logic which includes the floppy controller and RS-232C circuitry, all on a single board. The computer has two internal double-sided diskette drives and is the last model descended from the 1977 Model I. It retailed for {{US$|long=no|1199}} at its introduction in 1985. During 1987–1988 the retail stores removed the Model 4Ds from display but they were available by special order through 1991.

[[File:DGT-100 Brazilian TRS-80 Clone.jpg|thumb|DGT-100 by DIGITUS Ind. Com. Serv. de Eletrônica Ltda., one of a dozen brands of TRS-80 clones made by other companies]]