| Name | ATARI 2600 Video Computer System (also known as '2600 jr.') |
| Codename | - 'Bonnie'
- in the ATARI 2600 Development Kit, the machine was called 'ATARI MICROPROCESSOR GAME SYSTEM'
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| Made by | - ATARI Corp.
Sunnyvale, California - this one was produced in China (see serial number)
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| Released | - 1986 (CX-2600 jr. REV.A/ B/ C)
- the board-info indicates that this REV.F1 machine was made in 1991
- the very first VCS 2600 (model CX-2600) was introduced in June 1977 (on Summer-CES)
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| Serial-No. | X73 94 007581 |
| Additional Info | ATARI 2600
PAL-B
ATARI CORPORATION
MADE IN CHINA |
| Board-info | |
| CPU | UMC UM6507- the 6507 basically is a 6502 with only 13 external address-lines (A0-A12), thus limited to 8 KB address-range (in the VCS-design divided into 4K internal address space and 4K external, i.e. for cartridges). The 6507 also has fewer interrupt-inputs (no IRQ or NMI)
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| Speed | 1.182298 MHz (PAL)/ 1.193 MHz (NTSC)- PAL- and NTSC-machines seem to be clocked different. While NTSC-VCS have only one 3.58 MHz crystal at location Y1, the PAL-VCS have two: one clocked with 3.5468 MHz (used for color burst at Y1), a second with 4.433618 MHz (used for PAL color-encoding carrier frequency at Y2). Since NTSC-VCS create their CPU-clock by dividing 3.58 MHz by 3, I assume that shouldn't be different for PAL-machines (3.546894 MHz/ 3 = 1.182298 MHz)
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| RAM | 128 Bytes (128x8 SRAM), integrated in UM6532- was also called 'SARA' (e.g. in the Development Kit)
- this RAM can only be used for storing data, not program code
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| ROM/ Native OS | - cartridges with 2 to 32 KBytes capacity
- bankswitching was needed for carts greater than 4 KBytes, because the address space for 'external memory' is only 4KB in the 2600-design (and of course because of the cartridge slot's lack of more address lines)
- ATARI had created 'game standards', which came with the documentation of the development kits. These standards included the look of the games, or how they should utilize the machine's buttons. But what's far more interesting, it also included PAL/ NTSC/ SECAM-compatibilty! Having a look at the 2600-games today, it seems only few developers obeyed these rules, since most games will not work with different TV-standards...
Also interesting: that passage mentioned ('Foreign Versions') was omitted in the later 7800 game standards. Probably ATARI had given up on that?
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| Keyboard/ Layout | - none, but there was the ATARI 'Graduate'-prototype (never sold) which was a keyboard with its own CPU, OS and enhanced graphics
- has 3 switches on its back: one to switch between Channel 2 and 3 and two to set difficulty level for each port. Also has a button to switch between B&W and color-TV, as well as SELECT- and RESET-buttons (all three on its top)
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| Graphics | UMC UM6526P1 TIA ('Television Interface Adaptor')- Maximum resolution:
- there are no 'display modes'; TIA just outputs 'frames' with a maximum of 228 clock counts and 312 vertical lines (PAL)/ 262 lines (NTSC)
- the effective resolution is 160x228 (PAL)/ 160x192 (NTSC), because the frame contains 68 horizontal blank clock counts (HBLANK), 3 vertical sync lines (VSYNC), 45/ 37 vertical blank lines (PAL/NTSC VBLANK) and 36/30 overscan lines (PAL/NTSC)
- Maximum colors: 16 from a 128 color palette (16 hues * 8 luminances)
- TIA can generate 'playfields' (i.e. background) with a maximum of 5 movable objects (i.e. sprites), and provides collision detection
- this machine's a PAL version. For appropriate timing of TV-output (depending on the TV-standard), NTSC-VCS use the 3.58 MHz crystal at Y1, which also generates the CPU-clock. In PAL-machines, two crystal are used: a 3.5468 MHz at Y1 (color-burst signal) and a 4.433618 MHz at Y2 (PAL color-carrier frequency). Interesting in that context is that UM6526 is both PAL- and NTSC-capable, the TV standard is determined by board design (i.e. the additional crystal circuitry)
- TIA is direct predecessor to the ATARI 7800's MARIA, and the ancestor of CTIA and GTIA used in the XL/XE-series. It was later called 'Stella', which is also the earlier VCS' codename
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| Sound | generated by TIA- TIA contains two independant audio-circuits. Each can be programmed
- in volume (16 levels possible)
- to output sound at a given frequency (1-30 KHz) or
- to output various noises (noise-tone generator)
However, although both circuits can be used simultaneously, they only output to one speaker (i.e. mono) - in PAL-machines, sounds are generated with a lower pitch. That's because the crystal at Y1 (which clocks TIA) is slower (see 'Graphics')
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| Media | cartridges via 24 pin slot on its top (see 'ROM') |
| Input/ Output | UMC UM6532 RIOT/ PIA (interval timer/ timer IRQ, two 8 bit I/O-ports)
UMC UM6526P1 TIA (again) to trigger the joystick-buttons |
| Miscellaneous | - This 2600 jr.'s REV.F1 board looks very similar to my other 2600 jr. (which is REV.C). But there must be smaller changes, perhaps cost-reductive, because of the higher revision. And, of course, there's the slighly different case
- As already mentioned above, this REV.F1-machine was made in 1991. Thus, it must be one of the last machines ever produced, because ATARI stopped production of the 2600 jr. in that year
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