4 ms·

I wonder why they used a 68000? The 68020 was a significant upgrade, and other than not being a DIP package it made a great SBC.

by mark-r 6y ago

tyingq 6y ago
He did mention through hole being desirable. A DIP 16Mhz 68010 could be an easy upgrade. And you would get virtual memory addressing.
- icedchai 6y ago
  68010's still need an MMU for virtual memory. So do 68020's, now that I think of it.
  - tyingq 6y ago
    I see some evidence that an MMU is optional: https://news.ycombinator.com/item?id=7684824 https://news.ycombinator.com/item?id=7684824
    - icedchai 6y ago
      My understanding was the 68010 had "support" for virtual memory when used with an MMU due to improved exception recovery handling. For example, when accessing an invalid / unmapped memory address. See https://en.wikipedia.org/wiki/Motorola_68010 https://en.wikipedia.org/wiki/Motorola_68010 68000's didn't have that capability. An MMU of some sort would still be needed to implement the virtual-to-physical mapping of memory addresses.
    - noone_youknow 6y ago
      MMU is optional, unless you want virtual memory. The 68010 fixes a bug in the 68000 whereby it didn’t stack enough information to recover from an address or bus error, but you still need an MMU if you want to actually do virtual memory in any performant fashion.
  - mark-r 6y ago
    It might have been the 68030 that I was thinking of.
- snvzz 6y ago
  >A DIP 16Mhz 68010 could be an easy upgrade. Do you know how to source these? I can't even find the 14MHz ones, which I could use.
transitorykris 6y ago
Jameco was stocking the TI 68k earlier this year. Not certain what the author’s motivations were, but I picked one up after playing with the 6502 (their choice of vasm and the eeprom programmer are the same Ben Eater took off the shelf, coincidence?) The DIP package is convenient, at least until you see it comically take up 3/4 of a typical breadboard. Edit: yes, an opportunistic find at Jameco https://news.ycombinator.com/item?id=23993221 https://news.ycombinator.com/item?id=23993221

I wonder why they used a 68000? The 68020 was a significant upgrade, and other than not being a DIP package it made a great SBC.

by mark-r 6y ago

I wonder why they used a 68000? The 68020 was a significant upgrade, and other than not being a DIP package it made a great SBC.

tyingq 6y ago

He did mention through hole being desirable. A DIP 16Mhz 68010 could be an easy upgrade. And you would get virtual memory addressing.

icedchai 6y ago
68010's still need an MMU for virtual memory. So do 68020's, now that I think of it.
- tyingq 6y ago
  I see some evidence that an MMU is optional: https://news.ycombinator.com/item?id=7684824 https://news.ycombinator.com/item?id=7684824
  - icedchai 6y ago
    My understanding was the 68010 had "support" for virtual memory when used with an MMU due to improved exception recovery handling. For example, when accessing an invalid / unmapped memory address. See https://en.wikipedia.org/wiki/Motorola_68010 https://en.wikipedia.org/wiki/Motorola_68010 68000's didn't have that capability. An MMU of some sort would still be needed to implement the virtual-to-physical mapping of memory addresses.
  - noone_youknow 6y ago
    MMU is optional, unless you want virtual memory. The 68010 fixes a bug in the 68000 whereby it didn’t stack enough information to recover from an address or bus error, but you still need an MMU if you want to actually do virtual memory in any performant fashion.
- mark-r 6y ago
  It might have been the 68030 that I was thinking of.
snvzz 6y ago
>A DIP 16Mhz 68010 could be an easy upgrade. Do you know how to source these? I can't even find the 14MHz ones, which I could use.

transitorykris 6y ago

Jameco was stocking the TI 68k earlier this year. Not certain what the author’s motivations were, but I picked one up after playing with the 6502 (their choice of vasm and the eeprom programmer are the same Ben Eater took off the shelf, coincidence?) The DIP package is convenient, at least until you see it comically take up 3/4 of a typical breadboard. Edit: yes, an opportunistic find at Jameco https://news.ycombinator.com/item?id=23993221 https://news.ycombinator.com/item?id=23993221