58
votes
Accepted
Can anyone identify this unknown 1988 PC card from The Palantir Corporation?
This is a TrueScan board, which was used for OCR in PC AT systems. The board included a Motorola 68020 CPU, 2 or 4 MiB of RAM, and cost a cool $2,795 for the 2 MiB version (in 1988), $3,995 for the 4 ...
41
votes
Accepted
Why are the later revisions of the Motorola 68060 heavily sought after by Amiga fans?
Earlier revisions had some bugs (errata) but they still work fine and the problems can be worked around. For instance the MMULibs software checks the revision of the chip when the computer boots and ...
31
votes
Why didn’t the 1980s micros use MC68010?
Available isn't the same as in volume production, where big enough computer manufacturers could negotiate a better price in higher volumes. Both the Macintosh and the Amiga projects started out with ...
27
votes
Why didn’t the 1980s micros use MC68010?
While "why hasn't X been used" questions are inherently weak, still, one may consider some points:
While introduced in 1982 the 68010 wasn't available before mid 1983. Too late for any of ...
23
votes
How did the Sun-1 handle page faults despite having the original 68000 processor?
I haven't looked at the relevant versions of SunOS, so I can't say for sure which method they chose, but I'm aware of three methods for dealing with this problem.
The first method uses two CPUs. You ...
21
votes
Accepted
How did 68k-based Macs (or other contemporary systems) detect how much RAM was installed?
Yes, part of the POST sequence (which occurs before the display lights up) is a simple memory test which also serves to detect how much RAM is present. The Mac then sets up the hardware and its ...
19
votes
Why did Steve Jobs choose the Motorola 68030@25 MHz for the first NeXT Computer in 1988 and not an Intel 80386DX@25 MHz processor?
As far as I can tell almost nobody except the PC makers used x86. 68k was the more common architecture by far being in the Sharp 68k, Amiga, Macintosh, Megadrive, Sun-1, Vaxstation 100, and SGI Iris. ...
18
votes
How did the Motorola MC68030 and MC68040 come to have the powerful and expensive CAS2 instruction?
TL;DR:
TS, CAS and CAS2 work thru bus locking
CAS2 was introduced with the '020, the '030 had to have it for compatibility
While the 'cost' of locking for a complex operation is high, it's not ...
16
votes
Accepted
Why did Steve Jobs choose the Motorola 68030@25 MHz for the first NeXT Computer in 1988 and not an Intel 80386DX@25 MHz processor?
Very likely, familiarity with the Motorola environment and Motorola as a supplier within the development staff might have been technical reasons for choosing that CPU. After all, quite some of the ...
16
votes
How did 68k-based Macs (or other contemporary systems) detect how much RAM was installed?
(I was waiting Raffzahn to write an authoritative answer, but he hasn't yet, so I will write it myself.)
In General
Unless noted, sources are the Guide to Macintosh Family Hardware, 2nd edition, ...
15
votes
Accepted
Why was CPU32 core created, and how is it different from 680x0 CPU cores?
I can suggest why it was created. The Wikipedia page for CPU32 says:
The instruction set of the CPU32 core is similar to the 68020 without bitfield instructions, and with a few instructions unique ...
14
votes
Why didn’t the 1980s micros use MC68010?
The main thing which was absent in the 68000 but added in the 68010 was the ability to have an instruction execute until it attempts to access a protected region of memory, trigger a page fault, have ...
12
votes
Why didn’t the 1980s micros use MC68010?
AmigaOS never was intended to use virtual memory, basically it can only work when all processes are in the same memory space. Hence the features of 68010 you've listed were completely useless to Amiga....
11
votes
Accepted
MC68000: address error in initial PC
TL;DR:
There is no reason to add additional hardware to test especially for reset, or any vector at all for an odd address as that test is done by default with the first access using that PC, more so, ...
10
votes
Getting started for executing retro emulator-newbie
Frame challenge: That piece of software is not the place to start, as a newbie.
What that Github project provides is source code for a 68000 family processor emulator. But it's just a processor ...
9
votes
Why did Steve Jobs choose the Motorola 68030@25 MHz for the first NeXT Computer in 1988 and not an Intel 80386DX@25 MHz processor?
According to https://en.m.wikipedia.org/wiki/NeXT several people came with Jobs from Apple, including at least one hardware designer which presumably knew the 68000 family very well already.
My guess ...
9
votes
Can Access Fault Exceptions of the MC68040 caused by internal access faults occur in normal situations?
An internal access fault also occurs when the data or instruction MMU detects that a
successful address translation is not possible because the page is write protected,
supervisor only, or ...
8
votes
Why didn’t the 1980s micros use MC68010?
I can make some guesses. Price? Availability? Compatibility fears? They didn't know it existed?
In the case of the Atari ST, price was everything, so even a marginal increase in cost between the ...
8
votes
Why didn’t the 1980s micros use MC68010?
Having worked in the R&D section on product development, I can tell you that design of products is not instant. Sometimes, it can take a couple of years. If a chip was released to a ...
6
votes
How is a bus request initiated on the VME bus?
Although I don't have a deep VMEbus experience, maybe I can share some helpful aspects.
I've never seen a system bus arbitration initiated by software. A system bus like VME is meant to connect the ...
5
votes
How did 68k-based Macs (or other contemporary systems) detect how much RAM was installed?
RAM test was common (even ZX48K had it)... How it works:
it simply loop through "whole" address space and detects address mirroring and memory bugs.
something like:
// set system limit
max_adr=...
5
votes
Accepted
MC68030: does execution resume during or after cache burst refill?
According to the official 68030 User Manual, the '030 performs cache burst fills in critical-word-first order specifically to get the execution units running again.
However, accesses to the remaining ...
2
votes
How did 68k-based Macs (or other contemporary systems) detect how much RAM was installed?
Some machines required dip switches or jumpers. Some used memory probes. The Commodore VIC-20 and C64 used a non-destructive memory probe which would read each address, then try storing two distinct ...
2
votes
Accepted
Can Access Fault Exceptions of the MC68040 caused by internal access faults occur in normal situations?
It seems to me that this statement may be interpreted to mean that Internal Access Faults may happen normally even in a correct program as a side effect of the cache mechanism.
I just downloaded the ...
1
vote
How did the Sun-1 handle page faults despite having the original 68000 processor?
The original Stanford University Network computer design used a 68000. Several companies (Callan, Pacific Microcomputers, SUN, maybe others) marketed computers based on the Stanford design. I used ...
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