The theme this time is "loading (road)".Needless to say, the current home video game console has a loading, regardless of whether the game console starts, before the game starts, and even during the game, regardless of the stationary or portable type.On the other hand, there are many voices lamenting that the cassette of the "family computer" (hereinafter, NES) has lost the simplicity of playing immediately without loading.In the "PlayStation" (PS) version of "Ridge Racer", it is possible to play mini games, but the loading may be elaborate, but the waiting time is still the same.　

　A typical "decision complaint" that indicates that it is on the loading of programs and data in video games is "NOW LOADING" used in the previous "Ridge Racer".In recent years, this word, which has been used in game and animation -related songs and the title of novels, has been widely known to Japanese children in the 1980s."System" (hereinafter, disk system).When the "disk card" (disk medium) was inserted on the initial screen after the power was turned on, the boy and girl who watched "Now Loading ..." and watched over was a common sight at the time.

　In the first place, why is the loading that had already been accompanied by a personal computer before the birth of NES?Again from the basics, the storage device related to the CPU of the computer is roughly divided into the main storage device (main memory) and an auxiliary storage device (also called mass storage, but is called storage in this paper).Storage generally has the advantage of not being a primary memory, such as the cost per capacity.The loading featured this time is equivalent to a copy of the memory content from storage to the main memory, but the load destination may be a memory device attached to LSI (large -scale integration circuit) different from the CPU.

　By the way, as a basic principle common to the majority of CPUs, the program cannot be executed unless it is remembered in the main memory.Many arithmetic processing include the inside of the CPU and the range of the main memory.One of the solutions when there is no program that you want to operate in the main memory or the data you want to process is loading from storage.

　Conversely, if all the programs and data required for the predetermined operation are all in the main memory, there is no need for storage.The first combination of NES and cassette was true.

　So why did you have to introduce a storage called a disk system halfway, and the generations who were aware of the NES boom?On the other hand, some of the NES boom direct hitting generations have experienced the experience of "cassette software, but it feels like there is a lot of waiting time for some reason".What does this mean?

　To solve these questions, it would be quick to know the mechanism inside the NES.Also, following the loading circumstances on household game consoles, you can see why the current game consoles are loading.Let's get started.

* In this article, unless there is no particular note, "cassette" refers to cartridges such as home game consoles, not cassette tape.In addition, the capacity of the semiconductor memory alone should be indicated in bits if the accuracy is accurate, but is described in a byte unit to make it easier to compare with others.

Sentence / Tiny P

The cassette of NES was "a little strange"!?

　Here, let's look at the schematic diagram of the NES itself and the early cassette (the sound function and controller are omitted).In the main unit, there is a CPU and video LSI "PPU" as a major LSI, and RAM (random access memory) is connected to each.The RAM on the CPU side is a work area (work RAM) that writes data that fluctuates in the operation of the program, and the RAM on the PPU side is a video RAM (VRAM (VRAM)It has become.

　On the cassette side, there is a program ROM connected to the CPU (read -only memory) and a character ROM connected to the PPU.The content of the program ROM is a program or data executed by the CPU, which is the main memory of the CPU, like the work RAM (the diagonal part of the figure shows the CPU and its main memory).The character ROM stores characters, backgrounds, and character shape data displayed on the screen.

　The specifications of this cassette were actually a bit different in home game consoles at the time.One of the strongest stimulating NES developers is the Koreko Vision, a home game console from Colleco.Nintendo's "Donkey Kong" was transplanted as a sign title, and a prototype was shown in Nintendo in the spring of 1982.This model adopted the video LSI "VDP" by Texas Instruments (hereinafter, Ti), which is a mechanism to write both character data and placement information on VRAM connected to VDP.rice field.

　In such a configuration, only one ROM in the cassette is connected to the CPU side, at least one, and the manufacturing cost can be reduced.It is well known that the NES has been rotten to the cost reduction of the main unit, but why did the cassette need two ROMs?

　One of the major reasons is that when considering the specifications of NES, the model of the arcade version of "Donkey Kong" is modeled.In addition to this, in the business video game substrate at the time, the standard method was to connect the program and the character to the ROM, the ROM of the program was connected to the CPU, and the character data ROM was connected to the video circuit.。Furthermore, even in video games using older generation methods that make up rules and other rules only with logical circuits without using CPUs, the shape of the character may be stored in ROM [ *].

* For example, Sega's arcade racing game "Monaco GP" is applicable.

　On the other hand, TI's VDP was originally developed for the company's home PC, and it is considered that the priority of functions that could be changed by the user side.On the other hand, Nintendo was unnecessary for the time being because it requires a lot of RAM [ *].

* This led to the restriction that the character cannot be freely changed in "family Basic".

　In addition, if the cassette manufacturing cost is the highest priority, there is no way to use the CPU and PPU to share the same ROM.However, in this case, it is inevitable to use ROM in most of the time when the PPU is displaying the video, and if the design is not devised, the CPU side will have a lot of useless waiting time.Therefore, it may have been judged that the benefits of hiring were poor.

"Zevius" and "Super Mario", which was an issue for the lack of character patterns

　By the way, in the original NES cassette, the character ROM was 8 kilobytes (KB).This is equivalent to 128 types of 8x8 dots and 4 colors (one of them is a special color equivalent to transparent), and for 16 x 16 dots.Although the letters and backgrounds need to be covered in this range, it is generally necessary to compare it with the arcade video games around 1981-82.

　However, in subsequent game centers, more and more games have been trying to express the depth and vastness of the work world due to various characters and backgrounds.The lead is Zevius, which appeared in early 1983.The NES version, which was released at the end of 1984, almost two years after the appearance of the arcade version, recorded more than 1 million hits, but the character ROM was not enough.The character animation pattern has been reduced, and there is no terrestrial picture of Nasca, which was a specialty.In addition, many children would have realized the "difference in case" from the arcade because of the claims of the title screen.

　On the other hand, in the case of "Super Mario Bros." (hereinafter, Super Mario), which appeared in the fall of 1985, the NES version has a thorough optimization of data only for the original, and there is no seemingly obscure point.Still, the fact that the character ROM could be insufficient, for example, trivia is often told that "grass and clouds that grow on the ground use the same pattern just by changing the color."ing.

　One of the techniques used to overcome these limits is the "bank switch".If you use a large capacity of 16KB or 32KB for the character ROM, the top digital part of the "address line" that specifies the data position will not be directly connected to the PPU, and it will be too much.Therefore, in order to operate these, additional logical circuits and custom LSIs are incorporated into the cassette board, and the contents of the ROM are switched by program while using the program.

　The method of switching the bank itself was common in personal computers, but in the case of NES, it spread from third -party software such as Jaleko and Konami after late 1985.There is no doubt that both companies have been able to produce NES cassettes on their own.

　But Nintendo did not initially produce such a cassette.This is nothing but the aim of solving these restrictions at a stretch by introducing a disk system.From here, let's take a closer look at this disk system, which I mentioned at the beginning.

Both players and Nintendo are "Dreams spread" disc systems

　Instead of a cassette, the NES disk system is used by inserting a "RAM adapter" to the main unit, which also serves as an interface of the set product.Such a design, which anticipates function expansion via a cassette connector, is widely found in low -cost personal computers and home game consoles at the time.Nevertheless, it was extremely rare not only in Japan but also overseas to use a magnetic disk storage on a home game console.

　As a feature, the following three points are summarized in the following three points.

　Before and after Nintendo, before and after the development of the disk system, there were concerns that cassette software that cost more than 4000 yen will continue to sell in the future [ *].Even in the electronic game boom centered on "Game & Watch", manufacturers were criticized by "sensible" directions for selling expensive toys around 6,000 yen to children one after another.In addition, the boom ended in Japan at the end of 1982, and given the fact that each company suffered a lot of pain, it is not surprising that Nintendo is anxious.

* Masayuki Uemura "The beginning of the Japanese home game industry talked by NES developers" (3rd)

　Therefore, the adoption of a magnetic disk with low manufacturing costs reduces the price of the software, and provides it from casual software to masterpieces that do not fit in the conventional cassette.In addition, since the disc can be rewritten as a new work, there is no accumulation of bored software.In this way, the disk system was aimed at two birds with one stone.

The (developer) skill was tested!? Disk system

　By the way, in the RAM adapter of the disk system, as the name implies, the normal cassette program ROM and the character ROM are replaced with RAM.The capacity is 32KB for program RAM and 8KB for character RAM, equivalent to the first "Super Mario".On the other hand, the capacity of one disc was about 110KB on both sides, and it was sometimes described as "three cassette".

　Despite the same capacity as the cassette, the usability is different between ROM and RAM.In particular, program RAM can be used as a work RAM.In the 2KB on the main unit, it seems that the warshimulation game was quite difficult.Still, for less developers, the disk system would have been difficult to handle.Although it was unavoidable to keep the product price equal to the same as the NES (15,000 yen), it was a somewhat different mechanism from the general disk medium.

　The recording area of the disk system medium is an invisible but swirl -shaped band.Access is always done continuously from the top of the entire area, and it takes 5 to 10 seconds for one access [ *].It is possible to load multiple files with one access, but you can not load the file in front of it after reading the file recorded behind the disk, and divide the access into two times.There must be.

* Although it is out of the main subject, when writing data, access is performed at least twice, save (record) and verify (verification) to confirm that it has been completed properly.

　If the developer completes the software with only the capacity that can be loaded to the RAM adapter in one access, there is no problem.However, when dealing with a further amount, it is necessary to make the program and character data different from the first load and the additional amount.And if you don't think about the order of recording these on the disk or the steps of loading, you may have to repeat the actual game twice or three times.

　Of course, it is desirable to reduce the number of files as much as possible to reduce the number of loading as much as possible.It is also important to examine the game design stage, how to create a range that does not require loading in the game and how much it is separated."Metroid" is also an easy -to -understand example, but it is also effective to make it clearly recognized by players where loading is included, that is, where the "separation" is crossed.

　In other words, in order to develop software with a disk system and have less loading, there were various craftsmanship, in a sense, puzzle know -how.Even in the cassette version of Super Mario, considering that the lack of a shortage character ROM was supplemented by devising it, the difficulty would be increased by hanging a circle.

　Furthermore, as mentioned in the "Kusoge" times, the number of third -partys to enter the NES after 1985 is increasing rapidly, and all of these "new" developers have mentioned here.I wasn't able to pay attention.There was so many software that performed access three times, across the disk flip over before the title screen was displayed.

"Roading" for the cassette with "Mega ROM"?

　On the other hand, in the middle of 1986 in the middle of 1986, the Bank switched was used on the program ROM, and the so -called "Mega ROM", a one megabit (128KB) class.At this time, in addition to the method of switching the character ROM individually, the method of installing RAM on behalf of the character ROM, such as the disk system, is now used in some software.

　In the latter case, the character data will be stored in the program ROM, but if you use a bank switch, the character data can be hidden except when transferring to the PPU side.In this regard, it was more convenient for developers than a disk system.

　However, it was not always a good thing.In the disk system, basic processing and input / output system programs are provided in the RAM adapter, and data transfer to PPUs can be efficiently transferred.However, in the cassette, all of these processes must be programmed on the game software side.Depending on the developer's skills, it seems that the transfer of character data would take 2-3 seconds.In this way, the software came out, "I'm waiting for a cassette."

　By the way, Nintendo did not launch a disk system in NES, the Western version of NES.The cassette of the North American version of Zelda's Legend, which appeared in the summer of 1987, has a program ROM and a character RAM, an additional work RAM and a backup power supply.This will save play data.And the NES cassette has been introduced almost at the same time.

　In this way, among the features of the disk system, "expanding data" and "record of play data" can now be used in cassettes if we look at the increase in manufacturing costs.Then, for children, the disk system requires an additional expense as the main body, and the disadvantages of "some troublesome loading" are more prominent.

　In addition, as the "Dragon Quest" series and the like appeared, while the main axis of NES software became "heavy", two Mega ROMs, and 2 megabits (256KB) and ROMs were also used alone.For developers, the disk medium has been rather hooked.Disc system software since 1988 will increase the character of providing some niche software and past popular works inexpensive.

From the disk system to CD-ROM

　The time axis is slightly around, but in 1987, NEC's "PC engine" appeared, and the following year, Sega's "Mega Drive" appeared.Nintendo also released "Game Boy" in 1989, and "Super Nintendo" (SFC) was released in 1990, and the world of Japanese home game consoles changed significantly.All of these are written in the VRAM attached to the video LSI in the main unit.It is considered that the dominance of this configuration has increased as the RAM integration has increased and the price has dropped from the time of the NES. [ *]

* Regarding Sega, TI VDP is adopted in the same generation as the NES and the same generation, and it has been a common mechanism in Mega Drive.

　In addition to VRAM, CPU work RAM is also increasing.In particular, since the SFC work RAM had 128KB, the method of compressed data in the rom of the cassette was often used, and it was often used to expand it and write it in work RAM and VRAM.However, SFC has a weak point that CPU processing is not very fast, and it seems that there were some cases where players were "waiting".Later, some software equipped with a custom LSI that expands compressed data in the cassette.

　This generation stationary game console is also characterized by the fact that CD-ROM has been taken, led by a PC engine.The children who turned their backs to the disk system were presented with a significant increase in production on both images and acoustics, with a large capacity of up to 500 megabettes (MB) as a back shield.In other words, these were exchanged for loading "patience".

　Under these circumstances, it would not be necessary to list the "Neo Geo CD" of SNK, which was released in the fall of 1994, the last generation of the same generation, which was a game console that strongly impressed the display of "Now Loading".However, it cannot be overlooked that the mother's "Neo Geio" had a certain commonality with NES.First, let's take a look at the background that led to the appearance of the Neo Geo CD.