Sega Genesis (Mega Drive) Autopsy

[fantomfreq]

I recently ordered a used Sega Genesis off of ebay. I've been playing with it all week and earlier today decided to take it apart to clean it. Turns out that it didn't need to be cleaned but I did get some good pictures of the whole thing. Did this need to be done? Probably not. But I couldn't find any other pictures of a Genesis' guts on the internet, so this could potentially draw more traffic to the site (yeah, right.)

This is the top of the Genesis; it's nothing special. If I'm not mistaken, the Genesis is known as the Mega Drive outside of the USA. You guys overseas should recognize it. One should note that this is the second revision of the Genesis.

Once you take the top off, a protective metal plate is found. I don't think that this has much to do with heat dissipation as it wasn't in contact with anything that would be making heat.

This is the PCB with all the guts attached. Be warned, I left this file big so you could identify everything. I took this picture and identified most of the stuff that I could. It's pretty simple; I've seen mice that are more complicated than that thing. I can't seem to identify some of the ICs and I have no idea what the item is to the left of the cartridge slot.

I have two additional views of the console.

There is one other thing to note. The PCB is stamped with a date: April 5th, 1995.

[Staz]

I loved my Sega. It was the older one though. But it was attached to a Sega CD and a Sega 32x.

Anyone up for some sonic?

[fantomfreq]

Originally Posted by Staz

I loved my Sega. It was the older one though. But it was attached to a Sega CD and a Sega 32x.

Anyone up for some sonic?

I was literally JUST playing Sonic 2!

[Rondog]

Mod it!!!

Maybe some tri-lights on sound sensors. A clear top.

Then overclock it.

[Razorfish]

True.
Get that Red LED changed for a blue one!

[fantomfreq]

I've got a mod idea, though I don't have any tools on campus so it'll have to wait at least until spring break.

I'm thinking about some of this under the Sega and Genesis logos powered by one of these. I'll need to dremel out the logos, so this one must wait until I have access to something to do that with.

[Aedan]

Don't forget the import mods.

I presume you mean the metal item to the left of the slot? That's a voltage regulator. The chip you have marked as a "graphics processor" is pretty much the chipset + graphics + sound from memory!

[Pitch]

Originally Posted by Staz

I loved my Sega. It was the older one though. But it was attached to a Sega CD and a Sega 32x.

Anyone up for some sonic?

Hahaha... I still play mine, but only one game is ever played.

Gunstar Heroes. We played so much that we hold time trials on it to see how long it takes us to complete. 43 mins is about the record.

http://www.classicgaming.com/gunstarheroes/about.html

[dsio]

isnt sega genesis the one that is based on the motorolla Apple I chip?

[Aedan]

The core CPU on the Genesis is a Motorola 68000, a 32bit CPU that was released to market less than a year after Intel 16bit 8086 processor was. When IBM designed the PC, it was about two years after the release of the 68000. The PC hit the market in 1982, running DOS. The Mac hit the market in 1984 with a fully graphical interface, derived from it's predecessor, the Lisa (1983). By comparison, the PC had to wait until 1992 for Windows 3.1 to turn up.

The Apple-1 used a 6502 (8bit processor), the original Apple Macintosh used a 68000.

It's also possible to overclock a Genesis, if you don't mind soldering to the board. There's a couple of complications to do with keeping the sound processor in sync, but I know of Genesis overclocked to about 33MHz. See Epic Gaming for a bit more info on it.

[dsio]

heh. i was close.

Áedán your knowledge of cpus is both impressive and scary. You tried overclocking your Aibo? would be fun having an aibo on speed.

[Aedan]

No, I haven't but for good reason. The core of the ERS-210 AIBO (ERS-210 is modular) is a "brick" that contains both processors, the battery and the WiFi card. There's no ventilation, and there's nowhere to put a fan. Any heat buildup could cause serious problems. If you make the ERS-210 range work physically hard, then it's not unheard of for the environment monitor to shut the AIBO down to keep internal temperatures safe.

AiboPet took a Brick apart, so people could see. You can find it here.

[Gizmo]

Originally Posted by Áedán

The core CPU on the Genesis is a Motorola 68000, a 32bit CPU that was released to market less than a year after Intel 16bit 8086 processor was. When IBM designed the PC, it was about two years after the release of the 68000. The PC hit the market in 1982, running DOS. The Mac hit the market in 1984 with a fully graphical interface, derived from it's predecessor, the Lisa (1983). By comparison, the PC had to wait until 1992 for Windows 3.1 to turn up.

The Apple-1 used a 6502 (8bit processor), the original Apple Macintosh used a 68000.

It's also possible to overclock a Genesis, if you don't mind soldering to the board. There's a couple of complications to do with keeping the sound processor in sync, but I know of Genesis overclocked to about 33MHz. See Epic Gaming for a bit more info on it.

To be exact, the 68000 was a 16/32-bit hybrid. It used a 32-bit instruction model and ALU, but had a 16-bit data bus and a 24-bit address bus. The 68010 was just like the 68000, but with support for virtual memory management (it could handle a virtual 32-bit address space). The 68020 was the first 68000 family chip that had a 32-bit address bus. It also had support for manipulating 64-bit quad-word data (as two 32-bit chunks, thus requiring two 32-bit registers). The 68000 was designed as a follow-on to the 6800, and could even use many of the 6800 family peripherals (like the 6820 and 6821 UARTs), which was part of the reason for its 16-bit data bus. The 68000 (and its derivatives) was the heart of several PC designs in the mid-80's, including the Atari ST and TT families, the Commodore Amiga, and the Apple Macintosh (and Lisa). It also was the processor behind a number of video games from that era, including Out Run and Hard Drivin'.

The 6502 was originally created by inMos if I recall. inMos was founded by some disgruntled Motorola engineers, and their first product was the 6502, which was what they felt the 6800 SHOULD have been. It was an 8-bit CPU with a 16-bit address bus. The 6502 was the heart of many PCs from the early 80's, including the Atari 400/600XL/800/800XL/1200XL, Commodore 64/Pet, Apple I, II, IIc, IIe. There was also 16-bit extension to the 6502 (I can't remember what it was called now, the 65816 maybe?) that briefly appeared in the Apple IIgs, if I recall correctly. Gottlieb pinball machines used (and for all I know, may still use) a version of the 6502 chip sourced from Rockwell for their main processing. Most other pinballs (Williams, Bally, Data East, among others) used the 6800. GamePlan used a Zilog Z-80 (also a good chip).

With 54 instructions, the 6502 was a GREAT little chip to work with. There was a time when I could directly read 6502 machine code. There were also about 12 undocumented instructions in the 6502 design that were a result of a bug in the chip mask. 3 of those instructions had practical applications and were used in a number of games.

That concludes today's trip down memory lane. Hope you enjoyed the ride. LOL

[Aedan]

Gizmo, I think you missed out the 68008... As far as I'm aware, it wasn't heavily used, except perhaps for Sinclair's ill fated QL, and the ICL One-per-desk.

It was a 68000 with an 8bit data bus, but I don't remember the address bus size.

The 6502 was a nice processor - it was the first processor that I learnt assembler on.

[Gizmo]

Ya, I did miss the 68008. It had a 16-bit address bus, as I recall. It was designed to be a 6800 drop-in replacement, I believe (i.e. use the same socket) so allowing systems to be upgraded to 68000 code without having to redesign a bunch of hardware.

[dsio]

You know sometimes you guys take things a bit far :\
in any case, my 6800 has 16 pipes, and GDD3, and it owns your 6800 :\
you know, im starting engineering this year, but now in getting scared im going to end up like you two. you can really read 6502 machine code. By the way most people play with their robotic doggies rather than disecting them. poor little thing probably gets scared whenever it sees you Áedán.

[Aedan]

6502's an easy chip to learn.

Sony released the SDK for AIBO, so it's possible to write your own code. However, writing code for AIBO is a lot more interesting than writing code for Windows/Linux. You have to be aware that it's actually possible to hurt people if you don't follow safe programming rules.

Nutter's not scared of me. I'm not about to take him apart for a start!

As far as the engineering goes, it'll take a while to get to this stage. I've been hacking away at computers one way or another for too many years now.

[Aedan]

Back on topic - there's a couple of lines that generate higher frequencies that you could probably tap if you want to try overclocking the Genesis.

At least with the N64, it's easier to overclock - just change the bus multiplier.

[mashakos]

Originally Posted by Áedán

The core CPU on the Genesis is a Motorola 68000, a 32bit CPU that was released to market less than a year after Intel 16bit 8086 processor was. When IBM designed the PC, it was about two years after the release of the 68000. The PC hit the market in 1982, running DOS. The Mac hit the market in 1984 with a fully graphical interface, derived from it's predecessor, the Lisa (1983). By comparison, the PC had to wait until 1992 for Windows 3.1 to turn up.

The Apple-1 used a 6502 (8bit processor), the original Apple Macintosh used a 68000.

It's also possible to overclock a Genesis, if you don't mind soldering to the board. There's a couple of complications to do with keeping the sound processor in sync, but I know of Genesis overclocked to about 33MHz. See Epic Gaming for a bit more info on it.

That was the same processor on the Amiga 500 wasn't it? Except the Amiga had a few other Co-processors that made it more powerful.
33mhz!!! that's crazy! Does it make a difference with mortal kombat 2 ?