Comparison HP 9845 vs. Apple II and Commodore PET 2001
it was the year Star Wars and Saturday Night Fever hit the cinemas. And Fleetwood Mac released its Grammy-winning Rumours album, the Clash released their first album, and it is the year when Elvis Presley, the King of Rock 'n Roll died.
And several outstanding computers were released, including the Apple II, the Commodore PET, and, of course, the HP 9845. In fact, there was another home computer system which came into market in 1977, the Tandy Radioshack TRS-80, however simply because I don't own one, it is not yet included in this section.
So what's more obvious but to start a comparison of those systems, and see what made them successful. Each with its own features.
|Name||Apple II||PET 2001||HP 9845A|
|Manufacturer||Apple Inc.||Commodore Business Machines Inc.||Hewlett-Packard Co.|
|Type||Home computer||Home computer||Workstation|
|Year||April 1977||September 1977||September 1977|
|End of Production||1980||1982||1980|
|Number of units produced||40,000||unknown||unknown|
|Successor||Apple II+/europlus (1979)||CBM 3032 (1979)||HP 9845B (1979)|
|Built-in Language||Integer BASIC (Woz' BASIC)||Commodore BASIC 1.0 (based on Microsoft BASIC)||HP BASIC|
|Keyboard||Full stroke, 52 keys, caps only||73 key 'chicklet' keyboard with numeric keypad||Full stroke, 120 keys, (84 standard keys with numeric keypad, 36 special keys)|
|CPU||MOS 6502 (8-bit)||MOS 6502 (8-bit)||2 x HP Hybrid CPU (16-bit), nanoprocessor (8-bit) for internal printer|
|Speed||1 MHz||1 MHz||5.7 MHz (hybrid), 8 MHz (nanoprocessor)|
|Maths||Software (integer only)||Software (10 digits)||Hardware (12 digits)|
|Complexity||Single 2-layer PCB design (mainboard), 85 ICs (48 kByte RAM), all ICs socketed, separate switching PSU||Dual 2-layer PCB design (mainboard + CRT) 70 ICs (8 kByte RAM), all TTL chips directly soldered (sockets for RAM, ROM and processors only), PSU on mainboard with separate transformer||Design with 33 4-layer PBCs (20 mainframe, 5 PSU, 6 CRT, 2 tape), 500 ICs (162 LSI, 338 TTL) plus 10 ROM modules, only ROMs and nanoprocessor with sockets|
|RAM||4 kBytes (48 kBytes max.)||4 kBytes (early version) then 8 kBytes, plus 1 kByte video ram||24 to 72 kBytes|
|RAM Types||2104, 4116, 2116 (32 sockets), all DRAMs||6550 SRAMs, 2114 DRAMs (8 sockets)||2114 DRAMs|
|ROM||12 kBytes||14 kBytes||128 kBytes|
|Programming Languages||Integer BASIC in ROM (30 statements and 8 functions), Mini-Assembler in ROM, later Applesoft BASIC in ROM, also PASCAL, PILOT and FORTRAN on floppy disc||Adapted Microsoft BASIC in ROM (35 statements and 26 functions)||HP BASIC in ROM (130 statements and 45 functions, 19 operators), entensible with plug-in ROM modules, also PASCAL, FORTRAN, FORTH by third party on floppy disc|
|Text Modes||40 x 24 / 80 x 24 (with 80 columns card)||40 x 25||80 x 25|
|Graphics Modes||40 x 40-48 (16 colors), 280 x 192 (4 and later 6 colors)||None||560 x 455|
|Character sets||US ASCII (upper case only)||Full US ASCII, 64 graphics characters||Full US ASCII, international, 32 graphics characters|
|Character matrix||5 x 7 (within 7 x 8 matrix, upper case only)||5 x 7 (within 8 x 8 matrix)||7 x 9 (within 9 x 15 matrix) with true descenders|
|Text attributes||Normal, inverse, flashing||Normal, inverse||Normal, underline, flashing, inverse, or any combination|
|Sound||Single channel (by software)||None||Beeper|
|Size / Weight||18" x 15.25" x 4.5" (45.7 x 38.7 x 11.3 cm), 11.5 lbs / 5.21 kg||16.5” x 14" x 18.5” (42 x 36 x 47 cm) 50 lbs / 22.7 kg||19" x 18" x 26.3" (48.3 x 45.7 x 66.7 cm), 64 lbs. / 29 kg (without internal printer)|
|Monitor||Composite monitor (NTSC) ot TV set (with optional RF modulator)||Internal 9" TTL monitor (black & white)||Attached 12" monitor (black & green)|
|I/O-Ports||Video out (composite), 8 expansion slots, tape recorder (1,500 bps), game controller/paddles with 3 TTL and 3 analog inputs, plus 4 TTL outputs||Video out (TTL), IEEE 488 (edge connector only, no GPIB standard jack), parallel port, second cassette port for external cassette recorder, ''user port'' for 8-bit I/O, system bus||4 I/O expansion slots|
|Integrated Peripherals||None||Tape recorder (datasette)||High speed cartridge tape drive, thermal printer|
|Standard Expansions||Disc drive controller, super serial card, 80-character-card, Z80-card||Memory expansion||Graphics option, second internal cartridge tape drive, internal thermal printer, memory expansion, option ROMs, several interfaces|
|Power Supply||Switching PSU||Linear PSU (transformer)||Switching PSU|
|Power consumption||Max. 275 Watts|
|Price||$1,298 (4 kByte Version)||$795 (8 kByte version)||$11.500 (9845A)|
After starting with the Apple I as kit, the Apple Company quickly released their first fully functional personal computer, the Apple II. In contrast to later models like the Apple II+/europlus, the Apple II did not yet use AppleSoft BASIC, but rather Steve Wozniak's original Integer BASIC, and was available in configurations with less then 48 kBytes RAM.
Today's nimbus of apple products already has its roots in the Apple II design. It defintely had been one of the best industrial designs for home computers at the time, and - although as many features as possible were implemented in software and not in hardware - it was not a cheap design. Examples were the modern switching power supply (when most other home computers - if a PSU was included - used a linear power supply with heavy transformers), sockets for all ICs (even the TTL chips), 2-layer mainboard PCB design, eight expansion slots with edge connectors, and a full-stroke keyboard.
And it had been designed as an open system. Due to the eight expansion slots and available specs (including schematics), third party hardware was developed quickly. However it also did not last long until the first clones appeared (whether licensed by Apple Inc. or not).
On the other side, the Apple II was ready to use after a purchase only if you owned a monitor with composite video input. It needed at least an RF modulator for connection to a TV set, or an (at the time quite expensive) CRT monitor with composite input. Also, there were no real interfaces for peripherals included in the standard configuration, except game controllers, video interface and external tape cassette recorder.
Typical for the Apple II was the design of the floppy drives. For the Apple Disk II, Apple simply packed the plain Shugart SA 390 floppy disc drive hardware with any logic stripped off and without PSU into a small box, designed a minimalistic controller (more or less for electrically bridging to the system bus), and did the rest in software. As a result, the floppy drive provided 113 kBytes storage for $595, controller included.
And the Apple II already had color and sound. It seems that the Apple II had been the first commercial system offering bitmapped color graphics for consumers (I guess the Compucolor 8001 had been the first commercial desktop color computer around December 1976, which however provided 160 by 192 pseudo-pixels with graphics characters, similar to the later trs-80, but with 8 colors and including 19" color display for $2,690). In fact the color implementation was a hack, working with the NTSC system only. The Apple sends a short color burst on each scanline, which mimicries color mode to any NTSC monitor or TV, and then simply uses the pixel information as phase coded color signal. As a consequence, even the high resolution graphics mode could use color, without requiring extra memory for the color information. The sound circuit simply triggered a click on a speaker by writing to a defined memory location, which then could create tones and noise with an appropriate machine language routine. Analog input devices such as paddles and joysticks where sampled with another simple circuit, which just measured the time needed to charge a small capacitor.
Finally, the Apple II wedge-style appearance (designed by Jerry Manock) with its clear lines (including the vents) and proportions and the colorful logo simply was appealing. The first Apple II advertisement shows the Apple II in a home kitchen, not really conceivable for an HP 9845A or PET. And according to Michael Moritz in "The Little Kingdom", Jobs wanted to model the case for the Apple after guess what? After those Hewlett-Packard used for its calculators. He admired their "sleek, fresh lines, their hardy finish, and the way they looked at home on a table or desk..".
Apple Inc. did have a perfect promotion strategy: first the technical aspects were published as an article written by Steven Wozniak in the May 1977 issue of the BYTE magazine, and from that on every BYTE issue included a two or three full page color advertisement showing smiling people (like the aforementioned one with the kitchen) in it. Of course the guy on the ad obviously uses the Apple II for something serious (indicated by the uncontroversial line chart diagram...).
And color ads were quite uncommon for computers at the time. Just one year later, Apple already titled the advertisement with "Why Apple II is the world's best selling personal computer".
The Apple II shows to be surprisingly stable, even after more than 30 years, most systems still work.
Together with the TRS-80 and the Apple II, the Commodore PET had been the first personal computer manufactured in series. It featured 4 or 8 kBytes RAM (upgradeable to 32 kBytes with extension board), Microsoft BASIC in ROM and an IEEE488 interface for connecting peripherals. In contrast to the Apple II, it already included a CRT monitor and a tape cassette drive, and therefore was immediately ready-to-use after purchase.
And it was half the price of an Apple II. With some compromise, like the calculator-type keyboard, and the lack of sockets for all TTL ICs and expansion slots. Also, the PSU seemed to be a bit low dimensioned, so many PET users had problems with it.
The industrial design of the PET differs highly from that of the Apple II. Whereas Apple used a fancy plastic housing, Commodore designed its PET with sheet metal. Curious for the PET design is the way how the system can be opened just like an engine hood, and as such can be hold open by the use of a rod. All together, the PET was a nice piece of hardware for an almost unbeatable price. For me personally, the PET looked like borrowed from the 2001 Space Odyssey movie. In fact another HP 9845 model, the HP 9845C had its code name 'Odyssey' from the movie, but the PET design is much closer to it. Another funny thing is that HP called its workstations 'calculators', whereas Commodore named them 'computers', but supplied them with a pocket calculator keyboard.
The appearance of the PET with its sheet metal design was not as elegant and consumer-friendly as that of the Apple II with its molded plastics, although with concerns to EMI protection much better shielded. However, with its tetrazoidal monitor on a neck, which again based shoulder-like on the main casing, the PET looked somewhat anthropomorphic.
Commodore did not offer a comparable cheap solution for floppy discs like the Apple Disk II. The CBM 2040 dual disc drive was - although using the same Shugart SA 390 floppy drive hardware as the Apple Disk II - in fact a complete dual-processor computer on its own, featuring a complex IEEE488 interface and DOS in ROM, and sold with $1,295 for twice the price of the PET. Floppy disc storage with 170 kBytes per disc was somewhat more than the Apple Disk II, since Commodore used an adapted but unique (and therefore incompatible to anything else) sector partitioning for the CBM 2040.
Today, many PET systems suffer from defective ROM chips (similar to the HP 9845B series). Since the PET case is painted sheet metal instead of molded plastics, it keeps its original white color even after more than 30 years.
Before we go into the comparison, let's state that that it can't be a 'which is best' approach, since already the entry price ($800 vs. $1,300 vs. $11,500) is totally different. If we just want to compare home computers, we should do a comparison against HP's Series 80 (which arrived three years later), not against the 9845 series. More interesting is to compare different design principles and technologies, which all go back to the know-how of the same year, and maybe see whether the result justifies the difference of invest.
But let's start with Apple. Steve Wozniak, the inventor of the Apple I & II and co-founder of Apple Inc., worked after his study as employee of Hewlett Packard, where he tried to convince Hewlett Packard's 9830 project manager to get into the home computer business. However according to Wozniak, first HP decided that a home computer would not fit into the product line of HP, and - after Apple began shipping the Apple I - when HP finally started a 8-bit computer project with the Series 80 (still $2,750 for the simplest configuration) and their own 8-bit processor (code name "Capricorn") HP refused giving Wozniak the chance to participate in the development. So Wozniak finally decided to leave the company and concentrate on his work for Apple Inc.
The HP 9845A mainly had been the effort of HP to design a system with whatever seemed to be technically possible at the time. The product sheet as sketched by Jack Walden in fact had been some kind of an engineer's whish list, and initially wasn't really directed to a special target group or usage.
So, where now are the main differences to the "stars" of 1977?
Both the Apple II and the PET used the low-cost but easy to program 6502 microprocessor with a logic design much oriented towards the reference design for the 6502, whereas HP really downscaled their minicomputers along with its main system architecture into the three-chip 16 bit hybrid processor for the HP 9845A and the other system components. And the HP as a true multiprocessor system used two of those processors in parallel for freeing the main logic from all the I/O work. Also there were two separate 16 bit wide bus systems on the HP (one as memory bus and another for I/O), whereas Apple and PET used a single system bus.
All that were indicators for being a real workstation. Another point was that HP did a highly complex approach with twice the amount of R/W memory, seven times the number of ICs compared to the Apple II and the PET, and 33 PCBs again compared to one or two for the Apple and the PET. Also the 9845A was capable of doing floating point maths in hardware, which wasn't even an option for the Apple or the PET.
The system firmware of the HP 9845A was about ten times the ROM space used for the Apple or the PET, although all three used BASIC as the standard built-in programming language. The Apple II with its Integer BASIC was much a result of what Steven Wozniak thought would be useful for a programmer. It included a quite useful machine language monitor, but lacked string handling and any floating point maths. Later Apple licensed the common and more complete OEM BASIC developed by Microsoft and called it Applesoft BASIC. Commodore did this licensing from the very beginning and adopted MS BASIC for its PET system. HP focused primarily on the ANSI BASIC standard, and did its own extensions (resulting in something which had not much in common with ANSI BASIC any more). Some at the time unique features were identifiers with up to 16 characters, code indentation, variables with local scope, matrix calculations, interrupt processing, full debugging and tracing capability, dynamic or static extensions of the already rich command set, and the possibilty to save the full system state on mass storage for resume after powering down. Plus the ability to enter commands and change data while a program is running.
The software base for the Apple II mostly was provided by third party vendors, who took profit from the open overall architecture of the Apple and created most of all many games for it. For the PET there was almost no commercial software available, most programs were developed by hobbyists and distributed via computer clubs and bulletin boards. Hewlett-Packard produced a large number of professional programs for any purpose on its own, but also supported third party vendors and even provided an exchange program for royalty-free software. Most HP software was distributed on cartridge tape, however there were also many plugable firmware extensions which were later integrated in more recent versions of HP BASIC.
There is one interesting aspect comparing especially the Apple II, whose Integer BASIC can - just as its name suggests - only do integer maths but no floating point, to HP BASIC, which can do floating point maths (even supported by the processor in hardware) but no dedicated integer calculations. HP BASIC simply makes no use of the integer capabilities of the hybrid processor but calculates all maths with floating point, even if a variable has been declared as integer. Finally this prevents utilizing the speed improvement for all cases where integer maths is adaquate, but maybe the speed improvements showed not to be that relevant.
Obviously the HP 9845A was much larger and heavier than the two other systems. The high complexity and the integrated printer needed lots of space, which also had to be actively cooled. The Apple II with its 7 kg was a real light weight compared to the HP 9845A with its almost 30 kg. Even the PET - although totally built on sheet metal - was still 5 to 6 kg less heavy than the HP.
Human Interfaces and Peripherals
If a special component was needed, both Apple and Commodore bought it from the mass market. HP simply got it off its own shelves or developed and produced it right for the 9845A on its own. Also, HP tried to optimize the qualitity of the system, especially for the display and the keyboard, with much experience from its own terminal production.
HP already provided a number of high-quality peripherals like graphics tablets, which were all supported by the HP 9845A from the very start. Later models also included a light pen and soft keys as standard especially for menu driven interactions.
Apple designed the Apple II with ports for up to three paddle game controllers (which also could be used for a single joystick) with the breakout game in mind.
The PET had nothing comparable, however it was easy for the hobbyist to create his own solution by connecting a standard discrete game controller with a simple adapter to the PET's user port.
A sad chapter for the HP 9845A. There was nothing more but a simple beeper with fixed duration, volume and pitch. The PET not even had a beeper, but with its VIA I/O wonder chip and the user port, producing sound with an external amplifier in fact was an easy task at least for the hobby electronics user.
With the Apple II, games were part of the concept (Wozniak created the breakout game for Atari before he started with the Apple I development, still with the game in mind). However from the hardware view, it was at the first glance worse compared to the HP. There was just a click sound which could be produced on the speaker by reading from a certain memory address. But again, the concept of the Apple design to avoid anything producing hardware costs and do whatever possible in software simply outplayed the HP: The software simply has to produce clicks in the right manner to provide sound with up to eventually four independent channels, where the sound circuit of the HP is totally discoupled from any software control except generating always the same monotone beep.
The HP 9845A graphics option had four times the resolution of that of the Apple, and the PET lacked graphics at all (to be honest, the PET had a lot of graphical characters, which also could be used to produce some kind of pseudo-graphics with 80 x 50 'block pixels').
The Apple II used a simple but ingenious hack to produce color on an NTSC monitor, which therefore did not work for PAL/SECAM systems or RGB monitors (which weren't supported anyway). The HIRES graphics resolution is limited to 280 x 192 pixels. The graphics memory uses 8,192 bytes for a full screen, and each pixel is represented by just one single bit. That's common for monochrome graphics, but where is the color information? Now the Apple II has something like two palettes of four colors each (with white and black included in both palettes), which can be assigned with the most significant bit of every byte in the graphics buffer to the other seven bits which represent pixel on-off information.
Which color from a palette is finally shown in fact depends on the column of the pixel position (so actually the 280 pixels on a line are a bit of a fake concerning color, since color can't be assigned randomly to any pixel). This goes back to the fact that pixel clock in HIRES mode is exactly twice the NTSC color cycle, so that the position of the pixel determines the phase of the NTSC color signal. A perfect example for unorthodox but effective design.
Graphics are drawn by the processor simply by writing to the graphics memory. Some firmware routines written in machine language can be used to draw predefined vector images on the bitmap without destroying the background (a bit blitting technique called 'shapes' for the Apple II), which makes it possible to move animated objects over the screen.
HP had a strong interest in constructing a graphics display with outstanding quality. So HP's engineers kept a correct pixel aspect ratio, and built a high resolution (560 x 455 pixel) clear, crisp and steady display, but forgot to implement a direct access from the processor to the graphics memory (instead single pixel drawing commands were routed over the I/O bus) which finally limited drawing speed. So the display was used much more like a plotter and speed advantages of bit-mapped graphics were not fully available.
Later this concept was improved in that special graphics processors capable of vector generation were installed in the displays, which again made plotter like graphics lightning fast, but were still no replacement for bit blitting.
The most important difference of course was the target group, which finally decided on what influence the price has on the buy decision. The Apple II was made for the technically interested consumer, the PET for the technically skilled hobbyist, and the HP 9845A was constructed from engineering professionals for engineering professionals. So the colorful and non-technical advertisements for the Apple in the BYTE magazine appealed to the consumer user interested in computers, the PET was sold more or less by its affordable price, over its role as computer system for schools and by the information moving around among hobbyists, and it is not quite clear where HP placed its nice but not outstanding advertisements outside its own publications (if ever).
All were designed as desk-top systems, but simply reflected different classes of computers. The Apple II and the PET 2001 - although quite different in their appearance - finally were home computers which had been designed mainly under cost aspects.
But there are also similarities. For instance the idea of everything important integrated in the system, and having it ready-to run just after unboxing. All systems were well serviceable (which had been a much higher challenge for the HP than for the much simpler Apple and PET). The HP and the PET both shared the concept to connect peripherals over IEEE488, which not even needed a special interface for the PET. Both the HP and the Apple already used modern and efficient switching power supplies (which has become standard on todays PCs).
As a conclusion, Apple and PET represented perfect examples for personal computers, but the HP 9845A really was a workstation. And with the HP 9845A it was only the start which was continued in 1980 with the improved 9845B, the 9845C high end color system, and the high performance model 200 systems.