The truth about the Motorola 68000! 0001

This is a video debunking the old myth that the 68000 was vastly superior than anything else in its time.

Category:

Science & Technology

Tags:

• 68000
• 65816
• 6502
• 6809
• 6309
• ASM
• assembly
• programming
• cpu

[clownhorse]

I'm the only one with enough sense to not be brainwashed by people into thinking the 68000 (aka Adolf Hitler) is King Shit and everything else is tremendously underpowered.

[clownhorse]

The 65816 has MUCH better cycle efficiency than the 68000 if you REALLY knew how to program the 65816 to it's full potential. The problem is that everybody fails miserably with the 65816, simply because they are brainwashed in college to program every CPU like a 68000, and that the 68000 is tremendously overpowered and everything else is dogpoop.

[clownhorse]

The 65816 is a fair comparison because it was used in th Super Nintendo, while the 68000 was used in the Sega Genesis.

Everybody thinks the Super Nintendo's cpu is slow as shit, just because it is clocked slower and didn't have those stupid 32-bit instructions the 68000 has.

[clownhorse]

Usually the 68000 is cycle faster than the 6502, but sometimes the 6502 is cycle faster than the 68000. Here is a code to separate two nibbles from one byte. lda byte and #$0F sta first_nibble lda byte ror ror ror ror and #$0F sta last_nibble 24 cycles for 6502

[porcorosso81]

The 6502 may have a better cycle efficiency, but on the other hand, its severely limited amount of registers requires lots of memory loads and stores, and seperate operations to modify pointers in indirect addressing modes, where 68k has pre-post incrementing/decrementing. If you want to access more than 64K, you need bakswitching. Your rave about not needing 32bit arithmetic and logic is ludicrous. If I can manipulate 8 or 32 pixels per instruction on a bitmap is surely a big difference.

[pepshog]

"32-bit arithmetic and logic are completely useless! You never need to use any numbers that high!" - which planet are you on? I need to use 32-bit arithmetic all the time.

[68HC060]

True, true, true and true. But some things are a bit off.

I've been programming the 68xxx series through many years. Especially on the Atari ST, I wished I could move data faster than 400k/sec.

But here's what is not mentioned in the above "video":

With an 8-bit CPU, you can't write 16 bits in one go. You have to write two halves, which a 20MHz Atmel microcontroller can't do, unless you use a latch.

And it's wrong to say that 32bits were not needed for calculations. I used that *very* often.

[Shrapnoid72]

Very interesting! So the 68000 may not have been the only high grade CPU that turned out to actually be low grade.

Could you do a vid of pointing out the strengths and weaknesses of the HuC6280 and how it compares to the 68000? I would be very interested to see the results.

[TheFlyingJester]

From what I've seen, it worked like this:

Intel 8080 and 8086 failed. Everything else was pretty good.

[LordRenegrade]

Not use 32-bit arithmetic? Sooo you don't use floppy disks? hard drives? files bigger than 65535 bytes? Even the lowly 180k single-sided five inch diskette is storing 2.8x a 16-bit value worth of data. Or I guess that's just 360 blocks to you..

I'll see your 65816 or 6809 and raise you a 68060. Two integer ops per clock!

[DL3CE]

If you use LSR.B instead of ROR.W you save 8 cycles for the second AND because LSR fills with zeros from the left .. of course its slower but thats a very constructed example .. If you like something like that .. take your 6502 and reverse 512K 32bit values in memory in thier order and lets see which CPU is cycle faster now ;)

[DL3CE]

@DL3CE The 65816 and all the small 8bit CPUs (except for the 6809 which at least provided 2 Stackpointers, but no protection of the system stack) didn't implement any of this features like a protected "user mode". Sure, of course you don't need that on gaming consoles .. but gaming consoles aren't everything. If you read publications of the time, the 68k was definitly targeted to multiuser/multitasking systems .. and designed that way.

[DL3CE]

@DL3CE (even if protected virtual memory wasn't realized until the 68010, on the 68000 there were some design faults which allowed a user application easily to put itself in the supervisor mode and gaining full access to the whole system that way). In such enviroments the features it provided where essential and so the overhead was accepted.

[DL3CE]

@DL3CE (now = no) .. as everytime, it depends much on the application which CPU is faster. The 68k is clearly weak at "simple" tasks, because of its overhead. If the tasks get more complex, it gains advantage because of its powerful adressing modes and big set of internal registers. If you take a closer look at the architecture you see clearly that it's strongly inspired by the PDP-11. It was constructed to work in multi-user/multi-tasking enviroments..