SEGA Genesis VS Super Nintendo

Not having ever used either one or watched Ben's video, I went with the SEGA Genesis since it has a 68000 CPU.  I have very fond memories of programming and writing compilers for the 68000.  It's a very clean 32-bit architecture and... wait a minute... didn't you say this was a battle of 16-bit consoles?  Why in the world is a 32-bit 68000 considered a 16-bit machine?  Sure, it has an external 16-bit data bus but the internal architecture is all 32-bit.  That would be like saying an Intel 8088 is an 8-bit architecture rather than a 16-bit CPU with an 8-bit data bus.  Grumble grumble whine moan insinuate.

If you believe Wiki it seems its not sure if its 16 or 32 bit.

http://en.wikipedia.org/wiki/Motorola_68000

Guys

I was convinced from the start ...

I came into microcontrollers late, so I never did play with these, but it was certainly the day when the hardware and software limitations ensured the designers had to be clever.

So maybe we should report element14Dave poll as false or misleading??

Mark

How did you get this about IBM? Were you a CE?

Not sure if that is the scientific definition, but if I were to use a "32-bit" processor I would expect to be able to:

• Store 32 bit values in a single register and be able to use more than 1 32 bit register at a time.
• Perform basic 32 bit operations such as add, shifting, moving, and multiply and store the result in a single register. (add eax,edx or mov eax,edx)

For a 32 bit "system" I would expect to be able to read/write 32 bit values to memory in a single cycle and/or a single instruction.  I would also expect to be able to address somewhere in the vicinity of 2^32 bytes of memory.  I understand there is some overhead I need to take into account in those numbers but you get the point.

If I had a processor with only a 32 bit accumulator I would not call it 32 bit.  A system with a 32 bit processor and 16 bit bus in my book is not 32 bit.

I would however consider the "system" to be 32 bit if the processor is only 16 bit but there is an instruction set to move 32bits at a time across the memory bus in a single cycle.  I find memory moves, especially to a video buffer, are the most critical for gaming.

That's my definition.  Based on what I see in the videos both systems are 16 bit by my definition, which has not authority what so ever.

Clem Martins wrote:

 

How did you get this about IBM? Were you a CE?

I was an assistant professor for six years.  I taught two levels of computer architecture.  People like to malign IBM as a bunch of salesmen, but in fact IBM was the first to develop a lot of key computer technology.  For example, the IBM 360/91 (shipped in 1967) pioneered many pipeline speed-up techniques like out-of-order execution and register renaming.  A couple years ago I attended an ARM Techcon session on the then-new Cortex-A15 and its pipelining tricks.  It was pretty much the same material as my own lectures circa 1990.

Every your post I read I should add about 10 years to your experience. Just to be curious, how was the life with babbage ?

Joey Thompson wrote:

 

Not sure if that is the scientific definition, but if I were to use a "32-bit" processor I would expect to be able to:

• Store 32 bit values in a single register and be able to use more than 1 32 bit register at a time.
• Perform basic 32 bit operations such as add, shifting, moving, and multiply and store the result in a single register. (add eax,edx or mov eax,edx)

 

For a 32 bit "system" I would expect to be able to read/write 32 bit values to memory in a single cycle and/or a single instruction...

 

That's my definition.  Based on what I see in the videos both systems are 16 bit by my definition, which has not authority what so ever.

That's a good definition.  I also note that the SEGA Genesis case says "16-Bit" in large letters, so it's definitely declaring itself to be a 16-bit system even though it has a 32-bit processor.

OTOH, the original IBM PC considered itself a 16-bit computer even though it was an 8-bit system.  This distinguished the IBM PC from the popular Z-80 systems of the day.  The original Apple Macintosh considered itself a 32-bit computer even though it was a 16-bit system.  This distinguished the Mac from the IBM PC/XT/AT.  So the definitions are somewhat flexible, especially when marketing gets involved

The BeagleBone uses 16-bit wide memory, but it's clearly a 32-bit computer.  OTOH, that 16-bit wide memory is DDR, so you are getting 32 bits transfered per complete clock cycle.  But then does a 32-bit DDR give you a 64-bit system?  At a certain point the debate gets rather silly IMO

Enrico Miglino wrote:

 

Every your post I read I should add about 10 years to your experience.  Just to be curious, how was the life with Babbage?

Chuck was a good guy, but he spent all his time in his machine shop trying to make gears that meshed properly.  And people here complain about having difficulty soldering

(I once saw Babbage's lathe at the Science Museum in London.)

I think that this thread warrant pages of debate.  These are video games systems and this debate is not settled...

I guess if it can transfer 32 bits in a single cycle then it is 32 bits, despite only having a 16 bit buss.  But doesn't DDR have two 16 bit busses?  If so I would call that a 32 bit wide bus.

I wonder if they will ever go to a serial bus for memory?   Serial at the bit level that is.  Then we get a 1 bit bus and through more magic of marketing we have a million bit system?

screamingtiger

     Just like names and pseudonyms, much depends on the intent and not the actual usage. In computers there are variances in CPU, memory, cache, and bus which defines the architecture. It is not so important for the name but to understand the nuances so programming can be done as fast as possible. I have worked at low level and can tell you the 286 was a stupid chip relative to 386. Why? For the 286 to go from real mode to virtual was a simple setup and switch. But to return back on 286 to real for running those old programs took a soft reset of the processor which was nasty business if done wrong. Then they fixed that in 386. Intel has made many changes like this and others which drives low level assembler programmers to lose sleep at night. Look at my head

Clem

Joey Thompson wrote:

 

I wonder if they will ever go to a serial bus for memory?   Serial at the bit level that is.  Then we get a 1 bit bus and through more magic of marketing we have a million bit system?

That's basically what PCI Express is.  It replaces a 32-bit or 64-bit parallel bus with self-clocking multi-Gb/s differential pairs using 8b/10b encoding.  There's packet overhead so it's inefficient for single-word transfers, but block transfers are really high bandwidth.

The 8b/10b encoding used by PCIe (and Gigabit Ethernet and SATA and ...) is brilliant.  Any guesses as to who employed Al Widmer and Peter Franaszek when they came up with it?

Joey Thompson wrote:

 

I wonder if they will ever go to a serial bus for memory?   Serial at the bit level that is.  Then we get a 1 bit bus and through more magic of marketing we have a million bit system?

That's basically what PCI Express is.  It replaces a 32-bit or 64-bit parallel bus with self-clocking multi-Gb/s differential pairs using 8b/10b encoding.  There's packet overhead so it's inefficient for single-word transfers, but block transfers are really high bandwidth.

The 8b/10b encoding used by PCIe (and Gigabit Ethernet and SATA and ...) is brilliant.  Any guesses as to who employed Al Widmer and Peter Franaszek when they came up with it?

True John, the "clockless" protocol is more diffused than young technocrats can imagine...