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|The Learning Circuit|
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One of the first things Ben notices is that it has a multi-out on the back. It's been tested on an RF video connector from a 4K television to confirm modern televisions still use analog tuners. It also had a battery backup for your games. There’s also a slot for memory cartridge to allow you to have more backup spaces. There was also a RAM expansion that added more frames of animation to games like Street Fighter Alpha. Ben unscrews the Sega Saturn on the back to take a look at what’s inside. The top half of the enclosure has a nice mechanical spring-boarded lid. There is an LED with an acrylic light pipe over it to bring the light up to the indicator hole. It’s cheaper than making a separate circuit board. He disconnects the AC to DC Power Supply to take a look at it. It allows 9 volts at 3 amps, 5 volts at 2 amps, 3.3 volts at .6 amps, and ground. The assembly of this is quite similar to the PlayStation One, including the built-in power supply.
He removes the AC power switch with the capacitor on it. There’s a ribbon cable to control the CD ROM and another ribbon cable going to the controller port. If you were to make a portable of this, the CD ROM would probably be the most difficult part. You’d probably be better off with a SD to CD ROM replacement. The circuit board contains two CPUs. The best way to make your system easy to program is to have two CPUs, a master and a slave. On the back of the board is the ROM that is used when the system boots up, the bootstrap rom. There’s a multi-purpose ASIC to most likely do some sort of BUS arbitration. ASIC stands for Application Specific Integrated Circuit and is often used to replace multiple cumbersome logic chips. There are two 4 megabit chips to give the system 8 MB of work RAM for the CPUs, a separate combined chip gives you 16 Mb of work RAM. A control chip handles peripheral controls like the game controllers. The chip is near the add-on MPEG decoder. 90s computers couldn’t easily decode MPEG in software so they required additional hardware. A 4 MB memory chip is used for the CD ROM controller to cache the data coming off of the CD-ROM.
It has a total of 512 K cache which is more than the PlayStation prototype which only had 32 K cache. There also a system control chip. There’s also the VDP1 and the VDP2. These are the two graphic processors that handle everything in the system. One of them does the sprites which also become the polygons in the 3D games while the other one concentrates on backgrounds. It also contains a Motorola 68000, one of the most widely used CPU’s in history. Sega has taken the CPU of their previous system and used it as the audio controller of their new system. It is the audio driving CPU of the Saturn. They did the same thing with the z80 CPU on the Sega Master System and then used the z80 as the audio driving CPU on the Sega Genesis. Next to that, there is a Yamaha custom audio controller to allow the system to allow the system to do a good job at generating its own music and sound effects, rather than just streaming them off the CD. There is 4 Mb of RAM dedicated for sound. On the back there is a 2 Mb (256 K) RAM chip which is used for the internal battery backed saves. Ben totals up all the RAM on all the chips on the system.