Editing Commodore PET (section)

===Education, business, and computer science===
[[File:Pet4016.png|thumb|CBM Model 4016]]
[[File:Commodore 4040.jpg|thumb|[[Commodore 4040|CBM 4040]] dual disk drive (5.25-inch)]]
[[Image:CBM 8296-D.jpg|thumb|CBM 8296-D with two floppy disk drives]]

In 1980, the 4000-series PETs were launched. These included the enhanced BASIC 4.0, which added commands for disk functions and significantly improved [[Garbage (computer science)|garbage]] cleanup. By this point, Commodore discovered that people were buying cheaper {{val|8|u=KB}} and {{val|16|u=KB}} models of the 3000-series and upgrading the RAM rather than paying extra for the {{val|32|u=KB}} model. Because of this, they punched out the memory sockets in the 4008 and 4016 to prevent that practice. The 4032 was a major success in schools, where its tough all-metal construction and all-in-one design made it better able to stand up to the rigors of classroom use.<ref>{{Citation |last=Forster |first=Winnie |author-link=Winnie Forster |title=The encyclopedia of consoles, handhelds & home computers 1972–2005 |year=2005 |publisher=GAMEPLAN |isbn=3-00-015359-4|page=23}}</ref> Just as important in this role was the PET's otherwise underutilized IEEE-488 port. Used wisely, the port could be used as a simple [[local area network]] and allowed printers and disk drives (which were then very expensive) to be shared among all of the machines in the classroom.{{Citation needed|date=January 2011}} Unlike later Commodore machines, PETs had no kernel ROM functions for the IEEE-488 port and users had to write their own to use peripherals such as modems.

First year 4000-series PETs retained the same video hardware as the PET 2001/3000, but in 1981 this was replaced by the 12-inch screen and 6845-based {{abbr|CRTC|cathode-ray tube controller}} hardware.

The PET's simple, rugged design and completely enclosed components made it an early favorite in the North American education market. Schools preferred the 40-column models because the 40-column display's larger characters vs. the 80xx PETs were easier for young children to read. Commodore manufactured a variation on the PET called "Teacher's PET"{{snd}} these were relabeled 2001-series PETs which were donated by Commodore as part of a "buy 2, get 1 free" program offered to schools as part of a promotion/[[tax write-off]] scheme.<ref>{{cite web |url=http://www.portcommodore.com/dokuwiki/doku.php?id=larry:comp:commodore:pet:pet_faq-models|title=PET/CBM FAQ - MODELS OF THE PET/CBM}}</ref>

Two more machines were released in the PET series. The 8000 series included a new display chip which drove an 80×25 character screen, but this resulted in a number of [[software incompatibility|software incompatibilities]] with programs designed for the 40 column screen, and it appears to have been unpopular as a result. Unlike the 30xx series, the 40xx and 80xx PETs came standard with a 1-channel speaker for sound generation.

2001/3000 and 4000-series PETs used what became known as the "graphics keyboard". Numbers were exclusively on the [[numeric keypad]] and the row above the alphabet keys had only punctuation symbols. The 3032 and 4032 were produced in two special variants known as the B models with the so-called "business keyboard", which had a conventional layout with mathematical symbols and numbers above the alphabet keys. The keypad contained only numerals. On the other hand, all 8000-series PETs sported the business layout.

Entering graphics symbols on PETs with the business keyboard proved something of a challenge since they could not be directly typed out and usually it was necessary to display them indirectly via a CHR$ function.

The 4000/8000 PETs were more explicitly targeted at professional/business use than the 2001/3000. Business customers were the main target for the features of the enhanced BASIC 4.0, and a good selection of prepackaged business software was available.<ref>Commodore Microcomputers Issue 31</ref> A large line of 5.25-inch and 8-inch floppy drives were made for the PET family, and even 5 and 7&nbsp;MB external [[hard disk]]s. While they became fairly popular for business use in Europe, they failed to make much impact on the US market in part because the 6502-based PETs could not run [[CP/M]], which had become the standard for business software. In addition, the PET's {{val|32|u=KB}} of memory was a disadvantage against the Apple II and TRS-80, both of which could accommodate {{val|48|u=KB}}. The 8000-series PETs had a motherboard connector for a [[Expansion card#Daughterboard|daughterboard]] that added an additional 64K of RAM for 96K total; this was a standard feature on the 8096. A [[Hardware register|register]] at {{mono|$FFF0}} is used to set the RAM configuration. The extra RAM is banked in four 16K blocks, the first two blocks are switched into {{mono|$8000}}–{{mono|$BFFF}} and the second two in {{mono|$C000}}–{{mono|$FFFF}}. Normally, banking in the expansion RAM will swap out the video RAM, I/O registers, and system ROMs, so interrupts must be turned off first, but it is also possible to set the video RAM and I/O registers to "peek" through. Regardless, switching the OS ROMs out will require the user to either have interrupts disabled or supply their own interrupt handler. The expansion RAM cannot be seen by BASIC and machines equipped with the RAM board will still report the standard 31,743 bytes free on power up. A relatively small amount of software could utilize it.

As noted above, 8000-series PETs (and later 4000s) used larger monitors and a different video controller than the 2001/3000 models. This created a notorious compatibility problem known as the [[killer poke]]. On 2001/3000 PETs, there was a register which when enabled did not allow reading/writing of the video RAM except during the vertical blanking in order to prevent [[Noise (video)|snow]] on the screen, caused by the CPU and video controller trying to access the [[video random-access memory|VRAM]] at the same time. This feature was used because of the extremely slow 6550 SRAMs in the PET 2001, although it ceased to be a problem on 3000-series PETs since they used faster 2114 SRAMs for the video memory instead. Ordinarily, this feature was enabled on power-up. If the user did not mind snow, they could turn it off and get faster text output. BASIC programs and some machine-language software commonly did this for performance reasons. PETs with 12-inch displays (all 8000s and later 4000s) used a video controller based on the [[Motorola 6845]] CRTC chip (unlike the [[Transistor–transistor logic|TTL]] logic circuit in 2001/3000s/early 4000s) that eliminated the snow problem, but also placed a CRT control register in place of where the [[Vertical blanking interval|VBLANK]] flag had been on the 2001/3000. BASIC programs intended for the 2001/3000 thus had to be modified in order to run safely on 12-inch PETs. Later machines had modified video circuitry to prevent [[killer poke]] damage; a TDA 1170 chip was used in place of the original analog circuit so that if no sync went to the monitor, it would merely be shut off rather than send spurious signals.

The PET 2001 and 2001-8N had a register that would disable the video output; this was also used as output for the IEEE-488 interface, so screen flicker would occur during disk drive or printer use. It also became a popular method of producing explosion effects in games, but because the screen flickered while using the IEEE-488 port, the 16K and 32K models had this feature removed.

The last in the series was the SP9000, known as the SuperPET or MicroMainframe. This machine was designed at the [[University of Waterloo]] for teaching programming. In addition to the basic CBM 8000 hardware, the 9000 added a second [[Central processing unit|CPU]] in the form of the [[Motorola 6809]], more [[RAM]] and included a number of programming languages including a BASIC in [[Read-only memory|ROM]] for the 6502 and a separate ANSI Minimal BASIC-compatible BASIC for the 6809, along with [[APL (programming language)|APL]], [[COBOL]], [[FORTRAN]], [[Pascal (programming language)|Pascal]] and a 6809 assembler on floppies. It also included microEDITOR, a [[text editor]] for use in writing and maintaining programs for any of the 6809 languages. Also included was a [[Terminal emulator|terminal]] program which allowed the machine to be used as a "smart terminal" as well, so this single machine could replace many of the boxes currently in use at the university. Additionally this machine became a remote development environment where the user could later upload their creation to a [[Mainframe computer|mainframe]] after completing development and testing on the SuperPET.<ref>[https://www.commodore.ca/commodore-products/commodore-pet-the-worlds-first-personal-computer/ Commodore PET – The Worlds First Personal Computer]{{snd}} www.Commodore.ca</ref>

In 1982, Commodore retired the PET line with the intention of replacing it with the B-series machines; however, they were a marketplace flop and also very expensive to manufacture. Because Commodore still had a strong business software market in Europe, the 80xx series PET was revived during 1984 in a new molded plastic case with a swivel monitor. Four models were offered, the 8032SK, 8096SK, and the new 8296 and 8296-D. The 8296 models had 128K of memory (96K on the expansion memory board) and the 8296-D had two internal half-height 8250 drives. In addition, the 8296 came bundled with an office suite on disk and the system ROMs included a menu program to launch each of its four applications. Early units contained leftover 8032/96 [[printed circuit board|PCBs]] in order to get rid of remaining stock; after these were used up, Commodore equipped the machines with a new PCB that replaced the old triple-voltage 4116 DRAMs with more modern types.

The 8296 had a completely redesigned motherboard and handled expansion RAM in a different fashion than the 8096. While on the 8096, the expansion RAM cannot be accessed at all without switching out the OS ROMs and video RAM, the 8296 has a setup closer to that of the Commodore 64 where writing to the memory locations with the OS ROMs accesses the RAM underneath, but reading from those locations will read back the ROMs instead.

The 8296 also differs from the 8096 in that it has [[Jumper (computing)|jumpers]] on the PCB to select the power-on memory configuration for {{mono|$8000}}-{{mono|$FFFF}}. The factory default configuration was to have the I/O registers, video RAM, and ROMs occupying {{mono|$8000}}–{{mono|$FFFF}}. When operating from BASIC, the machine would be nearly indistinguishable from an 8032. By setting the jumpers, one could swap out any 8K region of upper memory for RAM, and it was even possible to have everything switched out and convert the entire {{mono|$8000}}–{{mono|$FFFF}} to RAM, although such a machine would be useless with no I/O or system ROMs accessible. Like with the 8096, the user could also manipulate the register at {{mono|$FFF0}} to control which RAM banks occupied upper memory. The 8296's RAM is banked in 16K chunks like the 8096, although since it has 128K, there are six possible banks instead of four, three that can go into {{mono|$8000}}–{{mono|$BFFF}} and three that can go into {{mono|$C000}}–{{mono|$FFFF}}, and like with the 8096, the video RAM and I/O registers can be set to "peek" through.

The motherboard also sported "user" jumpers which "connected" the RAM banking to the user port, these required soldering to enable. If connected, the user port could be used to adjust the upper memory configuration via software.

The IEEE-488–based PET disk drive line was also updated; the large, heavy metal-cased drives were replaced by smaller units in [[Commodore 1541|1541]] cases; they looked almost identical to a 1541 drive except for the back sporting an IEEE-488 connector instead of the two [[International Electrotechnical Commission|IEC]] [[DIN connector]]s. Of the previously extensive PET disk drive line, the only drives that returned were the 2031-LP and SFD-1001 (basically a 2040 and an 8250 repackaged in a 1541-style case with half-height drive mechanisms). The resurrected PET was sold through 1986 and then finally retired for good, having been superseded by the [[Commodore 128]], [[Commodore 1571|1571]], and [[Commodore 1581|1581]].

Although not officially a member of the PET series, in 1983 Commodore packaged [[Commodore 64|C64]] motherboards in plastic cases similar to the PET 4000-series in order to create the [[Educator 64]]. This was an attempt to retake some of the education market they had largely lost by then to the [[Apple IIe]].