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Model 1
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VA0 (JPN) |
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Components:
Due to a last-minute issue with the VDP in H40 mode, additional clock circuitry had to be added during manufacturing. This circuitry is present on a daughterboard in the center of the PCB, and contains the master oscillator (53.6931 MHz, NTSC), a 74LS74 (dual D-type flip-flops), and two 74LS161s (4-bit counter). | |
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VA1 (JPN) |
Components:
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VA2 (USA, High Definition Graphics) |
Components:
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VA3 (USA, High Definition Graphics) |
Components:
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VA4 (JPN) |
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VA4 (PAL) |
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VA5 (JPN) |
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VA6 (JPN) |
| Identical to VA5, but with TMSS implemented. This was also the first Japanese revision with TMSS on board. | |
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VA6 (USA, High Definition Graphics) |
Components:
Identical to VA5, but with TMSS implemented. This was also the first North American revision with TMSS on board. On some VA6 revisions, the unused female DE-9 port (used only by the Mega Modem in Japan) is removed. | |
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VA6.5 (PAL) |
| Identical to VA5, but with TMSS implemented. This was also the earliest European revision with TMSS on board.
The unused female DE-9 port (used only by the Mega Modem in Japan) is removed. | |
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VA6.8 |
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VA7 (USA) |
Components:
This revision is similar to the VA0 revision of the Model 2 in that it has a different M68K CPU and memory chips, as well as the sound and video chips being integrated into the main ASIC and different audio amplifiers (which resulted in different audio output from the previous revisions). The only difference is the Z80 CPU, which uses the same design as the rest of the Model 1 revisions. The YM2612 is now based on the YM3438, and is integrated into the main ASIC (the Sega 315-5487-01). A function on the VDP (integrated into the ASIC) has broken PAL 50Hz support. |
Model 2
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VA0 (JPN) |
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| PCB Printed by CMK
Components:
Redesigned board with differences in ICs from the Model 1 revision. New M68K and Z80 CPUs in a different form factor, the audio and video chips have been consolidated into an ASIC, and the audio amplifiers are different, resulting in a noticeably different sound output. The YM2612 is now based on the YM3438, and is integrated into the main ASIC (the Sega 315-5487-10). | |
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VA0 (PAL) |
| PCB Printed by TOWA | |
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VA0 (USA) |
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VA1 (USA) |
| PCB Printed by HDK | |
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VA1 (PAL) |
| PCB Printed by CMK
Components:
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VA1.8 (USA) |
| PCB Printed by SKS
Components:
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VA1.8 (USA) |
| PCB Printed by CMK
Components:
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VA1.8 (PAL) |
| PCB Printed by CMK
Components:
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VA1.8 (Asia) |
| PCB Printed by CMK
Components:
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VA2 (USA) |
| PCB Printed by CMK
Components:
This revision (along with the VA2.3) is the only Model 2 boards with a discrete YM2612 chip. Additional circuitry is present on the daughterboard located on the PCB, with model number 171-6961A. | |
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VA2.3 (USA) |
Components:
This revision (along with the VA2) is the only Model 2 boards with a discrete YM2612 chip. | |
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VA3 |
Components:
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VA4 |
Components:
This is the first Mega Drive board without any discrete CPUs. Both the 68000 and Z80 are contained with the Sega 315-5960 ASIC, as well as the VDP, YM3438, and I/O controllers. |
Model 3
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VA1 (USA) |
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Components:
IC3 and IC4 markings are silkscreened but don't correspond to any physical ICs. | |
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VA2 (USA) |
Components:
The tas function of the M68K (which was broken in prior revisions) has been fixed in this revision, making some games such as Gargoyles unplayable. |