Sega Master System Architecture: A Practical Analysis

https://www.copetti.org/projects/consoles/master-system/

by Parseus • 6 years ago

271 77 6 years ago

Something I didn't see mentioned: The Mega Drive/Genesis models 1 and 2 are backwards compatible with the Master System (but not the SG-1000) through a cartridge slot adapter called the Power Base Converter. If you have a Mega EverDrive, it can be used to play Master System ROMs.

wingi2• 6 years ago

Check the https://www.copetti.org/projects/consoles/mega-drive-genesis...

wingi2• 6 years ago

The Z80 cpu used in genesis for sound processing and it can used in the compatibility mode to run master system games.

kawsper2• 6 years ago

I feel like the SMS has the best sound from that era, but it might just be my nostalgia :)

"Escape in a Forest" from Ninja Gaiden on the SMS is my all time favorite: https://youtu.be/E3IWkLFfD6M but the whole OST is a masterpiece that does not get the credit it deserves.

bane2• 6 years ago

The music in the Double Dragon port is also quite fantastic.

https://youtu.be/U5OZBgayEJE

The FM module version is even better: https://youtu.be/fWlnsW3ywsI

I always get the sense that whoever did it was having a blast.

jnwatson• 6 years ago

That really brings me back. That was a heck of a game.

MrBuddyCasino2• 6 years ago

Interesting, I thought the SNES was much better due to its use of sampled sounds which sounded more naturally. It holds up amazingly well still today. I always thought the MegaDrive sounded plasticky and tacky, but it might very well be just because I grew up with a SNES.

dleslie4• 6 years ago

SNES is the next generation, with the Genesis/MegaDrive. SMS is NES era.

I prefer MegaDrive due to its distinctive sound; sampled audio lacks character. However, like with the GameBoy, it really matters what model you have. Rev 1 Genesis and grey brick gameboys have excellent sound.

musha68k• 6 years ago

Totally agree. SN76489 had a particularly dreamy 8-bit sound (BBC micro also used it AFAIK). Thanks for sharing (never played SMS Ninja Gaiden).

I never know if I would have preferred the music of the Yamaha YM2413 FM chip that was available as an extension to the Mark III and came with the Japanese Master System only.

It does sound great though - Yamaha YM2413:

https://youtu.be/Ug7qGWFnwC8

Texas Instruments SN76489:

https://youtu.be/9_NfVt7y_IQ

fullstop2• 6 years ago

Here's my all-time favorite from the 8-bit era: https://www.youtube.com/watch?v=Ls7rlhjazGo

Pictionary, of all games, had a fantastic soundtrack.

jtvjan• 6 years ago

That's Tim Follin for ya! https://youtu.be/GC1dTzyb5Gs

andrewf2• 6 years ago

Tandy PC compatibles (and the IBM PCjr) used the same chip. (Modulo differences in the RNG for the noise channel)

glhaynes2• 6 years ago

Why would it differ in the RNG, I wonder?

bane2• 6 years ago

Something kind of interesting, the architecture for the Sega 8-bit consoles (and the Sega 8-bit computer, the SC-3000) are extremely close to that of the Colecovision and the MSX 8-bit computers (which are in turn different, but very close to each other). Hobbyists regularly port games between the systems. There was definitely something in the air for Z80-based systems at the time. The Sega Game Gear is also almost identical to the Master System and can also play Master System games with an adapter.

Curiously, the Sinclair ZX systems also used a Z80 as the CPU and there are also a great many ports of ZX Spectrum games to the MSX computers, but those are a bit more complicated.

If you've never played SG-1000 games, they're worth it. The system had about the same power as the Colecovision, but the games are Japanese style games of the era vs Western games the Coleco mostly received. The ports are so stripped down that they're functionally demakes and it's often rewarding to see games just a bit too complex for the system stripped down to their core gameplay and graphics essentials. My favorite is the port of Elevator Action, which barely holds together, but somehow has all of the game there.

https://youtu.be/kUFgy6aVgbw

tenebrisalietum• 6 years ago

I think the Z80 was overall, due to its instruction set, the 8-bit CPU of choice unless the system builder needed to be cheap; and this makes sense given it was pretty much engineered to be a cheaper CPU than the Motorola 6501.

So it made sense that Commodore used a 6502 variant and I'm betting Nintendo chose a 6502 core for its NES to keep costs down. But all your old Japanese 8-bit arcade games of the 80s were Z80-based.

fullstop2• 6 years ago

My trusty graphing calculator, a TI-85, also was Z80-based.

philistine• 6 years ago

The Famicom used a 6502 clone from Ricoh in part because that’s the only thing they could find; every other chip manufacturer had too much backlog. They had already used the Ricoh chip in arcade boards, and just went with that one.

timbit42• 6 years ago

While more computer and console systems were designed with a Z80, the 6502 computers and consoles vastly outsold the Z80 systems.

The Z80 has more powerful instructions but they take longer to execute. The 6502 instructions are faster but you need more of them to do the same task.

In the end, a 1 MHz 6502 was almost equivalent to a 3 MHz Z80. The Z80 was available up to 4 MHz but often ran at 3.58 MHz) and the 6502 was mostly 1 MHz (eg. Apple II, Commodore 64) but in a few systems (eg. BBC Micro, Commodore 128) it was 2 MHz.

krallja4• 6 years ago

Motorola made 68xx, MOS Technologies made the short-lived 6501 which became the famous $25.00 6502 with some tweaks.

ezconnect2• 6 years ago

MSX was an industry standard of making home PCs so it's easy to port softwares.

pavlov• 6 years ago

And the MS stands for Microsoft.

MSX was the original Xbox.

thought_alarm• 6 years ago

The TMS9918 video chip is the common thread between those machines, and it's a fascinating bit of hardware.

The interface between the TMS9918 and its host system is dead simple: 8 data bits, 1 mode bit, 1 chip select bit, and nothing else. It manages its own 16 kB of VRAM and no other timing or clock signals are required between the 9918 and its host CPU.

As a result it was used in all sorts of machines of the era: TI 99/4A, Colecovision, Coleco Adam, MSX, Sega SG-1000, plus multiple different expansion cards for the TRS-80 and Apple II. It also supports genlock video input and was used in early-80s video production.

Most importantly, its programming interface is well defined and extensible. It allowed Yamaha and Sega to produce upgraded chips for the Sega Master System and MSX2 while maintaining backward compatibility, something that Commodore wasn't able to do with the VIC-II chip in the C64.

tr352• 6 years ago

The TMS9918 is as simple as it is beautiful. A couple of years ago I wrote an MSX emulator in Java for fun. A pretty accurate TMS9918 emulator took just a couple of hours to write with the original technical handbook at hand, in 561 lines of Java code.

https://github.com/tjitze/TMSX

krallja4• 6 years ago

I am making a Youtube video series about the TMS9918A. So far, I’ve driven it with an Arduino and a 6502. The next video will get VRAM hooked up.

https://www.youtube.com/playlist?list=PL3itg4Usn3F-24qjSrlY4...

jecel• 6 years ago

In late 1981 I built a computer around the Z80, TMS9918A (actually 9928A as I wanted PAL-M output) and the TMS5220 voice synthesis chips. I called it "Einstein" and only found out decades later that there was a computer from Tatung with the same name, processor and video chip that sold in the UK in 1984. Great minds think alike, it seems...

I was not able to get a datasheet for the 9918 and had to abandon the project. In early 1983 I did get a nice book from Texas Instruments by asking them to send it to an address in the US, but I only skimmed it. That was a huge mistake. A few months later I started a new computer project for the Logo programming language and remembered that Logo in the TI99/4 kept "running out of ink". There were only 256 different characters which could be redefined but the screen was 32x24 = 768 characters in size. So 2/3 of the screen had to be blank as the turtle moved around it. So I went with the Motorola 6883/6847 combo instead (the same as the TRS-80 Color Computer).

It so happens that the TMS9918A used in the TI99/4A has a new mode that the TMS9918 didn't: you can divide the screen in 3 with a different character set for each part. That would have given me Logo with infinite ink.

jandrese• 6 years ago

I think some of this is just that the industry was really small at the time. If you wanted a processor there were only a handful of choices, and most were completely unsuitable (too expensive mostly) for the home market. Low cost graphics and sound were similarly small markets. But it was also a wide open field in the home console biz, especially with ATARI spectacularly imploding only a few years earlier, so lots of people were throwing their hat in the ring and building the kind of system that made the most sense given the available parts.

tosh• 6 years ago

@ variants: there is also the Game Gear, a handheld by SEGA with similar specs to the Master System

https://en.wikipedia.org/wiki/Game_Gear

With a late start into the handheld gaming market, Sega rushed to get the Game Gear into stores quickly, having lagged behind Nintendo in sales without a handheld on the market. As one method of doing so, Sega based the hardware of the Game Gear on the Master System, albeit with a much larger color palette than its predecessor: the Game Gear supported 4096 colors, compared to the 64 colors supported by the Master System. Part of the intention of this move was to make Master System games easy to port to the Game Gear.

onion2k• 6 years ago

I had a Gamegear when I was at school. It was a great console but it ate batteries at an insane pace.

paulmd• 6 years ago

The external battery packs (first a wired pack about the size of a 6" sub sandwich, then the battery back) were pretty much a mandatory accessory.

grecy2• 6 years ago

The power cord from the Master System II was a direct plug in. I must have played thousands of hours wired like that.

christoph• 6 years ago

You could also get a really simple adapter to plug Master System cartridges straight into the Game Gear

https://segaretro.org/Master_Gear_Converter

ibdf2• 6 years ago

My first video game. That design was way ahead of its time.

rm445• 6 years ago

I don't get the impression that it was - it came out later than the NES and was a bit more powerful, but much less so than the 16-bit systems.

There are some (relatively) impressive games for the Master System, but I think that's because it stuck around into the nineties, in regions where there was an installed base i.e. not the USA. Late-generation games often benefit from better optimisation, and things like more cartridge space. The Master System port of Mortal Kombat, for instance, despite being pretty horrible as a game, is miraculous from a technical point of view. Despite being heavily cut-down, of course, it was an attempt to create the same game. That's a port (or demake or whatever else you'd want to call it) of a 1992 arcade cabinet, onto a home console released in 1985.

ibdf2• 6 years ago

The Master System and the Mega Drive (Sega Genesis) were huge in South America where I grew up. They were also a lot cheaper than SNES and more widely available.

snarfy• 6 years ago

If you turned the system on without a game in and you held up, 1 and 2 all simultaneously, there was a secret game built in to the system. When my friend got his SMS he did that on accident the first time he turned it on, leading to much confusion.

https://en.wikipedia.org/wiki/Snail_Maze

JNRowe• 6 years ago

Welp, there goes an hour in the rabbit hole¹.

¹ https://www.smspower.org/Development/BIOSes

kawsper2• 6 years ago

My SEGA (sold in the EU) shipped with Sonic installed, it booted Sonic if no cartridge were detected, interesting that it started as a hidden game.

grecy2• 6 years ago

The Master System II sold in Australia had Alex The Kidd as a built in game...

stonedge• 6 years ago

I saved my paper route money and was trying to decide between an NES and an SMS. I think I chose the SMS because it was different. Everyone had an NES. But as time went on, I wished I had an NES. Way more games and cultural relevance.

lostgame2• 6 years ago

Sega Genesis / Mega Drive was the first console I learned to program for, maybe when I was about 11-12 or so and was getting a start at ASM when I found hex editing too limiting in the ROM hacking scene.

The Genesis/MD uses a Z80 processor as its sound processor alone - so it is amazing to me to consider running everything off that on a Sega Master System!

I'm a little obsessed with Sega Saturn homebrew at the moment, or I'd try some SMS homebrew - but the article was fascinating!

Grazester• 6 years ago

Sega Saturn homebrew? I though that was an oxymoron. I love my Saturn like there is no tomorrow but it seemed like to me the homebrew sense was dead due to the whole system architecture. The only thing I hear about is the Z engine which is insane in its capabilities.

https://www.youtube.com/watch?v=JPYEiDwZbRc

lostgame2• 6 years ago

https://jo-engine.org

Is a fantastic open-source homebrew platform for the Saturn that the Z-treme engine is based off of.

I recall watching all the phases of the Z-treme's engine's development on the jo-engine forums as XL2 was creating it. So cool to watch. :)

mark_mcs• 6 years ago

It's a shame the scene is so quiet as the Saturn is a fascinating machine. If you use something like Jo Engine then it's not too difficult to get up and running. If you want to roll your own and still have something that performs it gets messy. Stuff like dealing with bus contention between the SH2s, the VDP access timing/slot system, that funky little DSP. You can see why it took so long to get decent libraries for it. It's still fun to see how far you can push the hardware.

sehugg• 6 years ago

The VDP's Mode 4 was the secret sauce; it made the SMS graphics almost on-par with the NES. You still have 8x8 tiles, but with a single 16-color palette instead of four different 3-color palettes. For scrolling, the NES has 2-4 screen buffers, but the SMS just lets you hide one single row and column of tiles offscreen. This isn't as bad as it sounds since -- on SMS you can write to VRAM at any time during the frame, as opposed to NES where you can only write during vertical blank.

I've ported a simple NES game written in C to the SMS (https://8bitworkshop.com/projects/?n=sms-sms-libcv/chase) and I think it'd be feasible to write a translation layer between the two platforms. Sound might be a little tricky, since NES's APU is more advanced.

bennysonething2• 6 years ago

Can someone explain, does s Japanese master have better sound? From clips it sounds 100 times better.

christkv• 6 years ago

They had an additional fm synth chip that was not present in the us and European models from what I remember.

Parseus• 6 years ago

Japanese Sega Master System (and older Sega Mark III when used together with the FM Sound Unit) had an additional Yamaha YM2413 sound chip.

bennysonething2• 6 years ago

Thanks, the megadrive actually has the master system hardware in it. I've got an everdrive and I can play master system ROMs on it. It's actually a Japanese megadrive that I own, I want to dig it out and see if the sound is better!

JohnBooty• 6 years ago

If you're interested in seeing what the Sega Master System can do when it's pushed to its absolute limits:

Blast! demo (2017), pulling off some crazy rotation and perspective effects https://www.youtube.com/watch?v=I742MvGhkME&feature=emb_logo

"Games That Push the Limits of the Sega Master System" https://www.youtube.com/watch?v=H4Ze11Z8ffU

Road Rash - This is unbelievable. Visually, it's nearly up to the standards of the Genesis version. Although of course the Genesis version didn't run at a particularly high frame rate. https://www.youtube.com/watch?v=SlfLgnE6OIw

pacomerh• 6 years ago

speaking of SEGA, Twisted Electronics just released an FM synth that uses a pair of FM audio chips (YM2612) similar to the one discussed in the Sega Master, this one is from the 'Mega Drive'. https://twisted-electrons.com/product/megafm/

wyldfire2• 6 years ago

SMS came with Sonic the Hedgehog? Interesting! I thought it was introduced with the Genesis.

krallja4• 6 years ago

It was! The 8-bit SMS/Game Gear version was introduced in 1991.

sjwright2• 6 years ago

Though it was not a port, rather a completely different game developed by a completely different team. It was a good game in its own right, but it’s not comparable to the 16 bit original.

wyldfire2• 6 years ago

Oh..so was it a port? Hadn't the genesis been introduced by then?

fernly• 6 years ago

Sorry, I find the article impossible to read owing to the spidery font rendered in 50% gray. Who thinks that is a good idea?

syspec• 6 years ago

Always in awe of articles like these, where does a person with this kind of knowledge work?

Sega Master System Architecture: A Practical Analysis

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