Amiga questions you've always been too embarrassed to ask

[Daedalus]

It was probably a fabrication process upgrade that meant the part could run quicker without actually changing the design of the chip much. Since they only run them at ~0.7MHz, it makes no difference which one was used, and so they'd use up the old parts before the new ones, or whatever they happened to have available on a given day.

Edit: This thread gives more details, so it is indeed the -01 part that has the "bug", or at least, different behaviour. But it's very much an edge case so nothing to worry about in normal usage.

[NLS]

If I recall, C64 runs CIA faster than Amiga... I might be wrong though.

[Fastdruid]

Originally Posted by NLS

If I recall, C64 runs CIA faster than Amiga... I might be wrong though.

I'm not sure you are. A google suggests that the C64 ran at 1MHz while the Amiga CIA's ran off the "e-clock" which is 1/10th of 68000 bus speed (so roughly 0.7MHz).

[Predseda]

Question: What is the difference between CLI and Shell?

[NLS]

Well it is just a matter of history.
Amiga when it started (up to I think 1.3) , had access to command line through the CLI (Command Line Interface).
Later the CLI got enriched and was renamed Shell (in the likes of *ix "shells"), but it was the same thing in practice.

You can actually end a Shell session both by endshell and endcli.

[Jope]

Originally Posted by Predseda

Question: What is the difference between CLI and Shell?

Up to 1.2 there was only CLI. No command line editing, no resident commands, no aliases..

Release 1.3 provided us with a shell with all kinds of nifty features and also a new console handler to go with it called NEWCON:. Now we had those resident commands and command line editing etc. These components were not built in to ROM, but instead loaded from disk. Probably a mixture of a lack of ROM space and wanting to keep backwards compatibility. Read the 1.3 enhancer software manual to read about the new features the shell brought along. https://issuu.com/ivanguidomartucci/...re---ebook-eng

2.0 had NEWCON: renamed into CON: and the shell became ROM resident. From here onwards, CLI and Shell are the same thing. The newcli and endcli commands are still there for backwards compatibility.

[marcfrick2112]

My embarrassing question: I kinda know what preemptive multitasking is, but why is it (supposedly) better than other types of multitasking, and for that matter, what ARE the types of multitasking?

[Fastdruid]

I'll try an EL5 explanation.

I'll answer it in reverse. There are two main types Cooperative multitasking and Preemptive multitasking.

Cooperative means that each application itself has to voluntarily give time so that other things can run. Until it does so it will hog all of the CPU and the system will be unresponsive until that program has finished what it is doing.

Preemptive means that the operating system allows each running program a slice of time and swaps between them regardless of what the process is doing so that each program gets some processor time. No one process can hog the CPU and the system will remain responsive (even if the one program isn't).

The reason that preemptive is better is because one (badly written or buggy) process cannot hog all the processor time and software doesn't have to be explicitly written to take advantage of it.

There is one reason that cooperative is better and that is because it allows for simpler applications because execution is never unexpectedly interrupted.

If you imagine that the CPU is a pie, preemptive is giving everyone the same size slice, cooperative is letting everyone agree what size slice they should have...and if you get a bully they'll take it all!

Now in reality the size of slices isn't the "same" because it's actually based on priority and interrupts (as well as if a process actually _needs_ all that time) etc but you get the idea.

[Daedalus]

Originally Posted by marcfrick2112

My embarrassing question: I kinda know what preemptive multitasking is, but why is it (supposedly) better than other types of multitasking, and for that matter, what ARE the types of multitasking?

At the time, the main alternative (which was used by Windows and MacOS up until NT/Windows 95 and OS X) was cooperative multitasking. Basically speaking, in preemptive multitasking, the code just goes ahead and runs, and the OS steps in whenever a task switch is needed, pauses it and deals with all the registers, stack etc. that the program was using. When the OS decides it needs to run that code again, it restores the registers and state of the machine so that the code just carries on as if nothing happened.

By contrast, cooperative multitasking requires that multitasking support is included in a program's code. When this sort of code is running, it takes over the machine until it decides to release it for other programs to use. So each and every program gets to decide how much CPU time it uses, and so if anything doesn't play nice and hangs onto the CPU for too long, everything grinds to a halt until it's finished. This could be a program trying to load, a crashed application, a render or something like that, perhaps where the developer hasn't explicitly broken up a long operation into smaller millisecond-scale chunks to allow other programs to run.

[morch]

my silly question is: if i do the jp2 mod to my rev 6a board so i can use the 1mb chip ram - if i unplug the expansion, will the amiga work ok?

[brett71]

Originally Posted by morch

my silly question is: if i do the jp2 mod to my rev 6a board so i can use the 1mb chip ram - if i unplug the expansion, will the amiga work ok?

Yes, it will be fine, but you'll just have 512KB of CHIP RAM, and 0 FAST RAM, unless you've got something besides the trapdoor connector providing FAST.

[morch]

Originally Posted by brett71

Yes, it will be fine, but you'll just have 512KB of CHIP RAM, and 0 FAST RAM, unless you've got something besides the trapdoor connector providing FAST.

oh excellent, i have one of the DJcook ide & 8mb fast ram adaptors, but i was just hoping it wouldn't brick my amiga

if only i can solder properly now

[wiz12]

Is there any difference between the A1200/A4000 Lisa CSG 391227-01 and the HP 391227-01 version?

[Jope]

Different fab, but almost certainly the same masks and a very similar process.

[WinstonF]

Here's my embarrassing question, it's about viruses, I'm sure it's been asked before so happy for the mods to move it to the correct place etc.



QUESTION: Was there ever a virus on the Amiga500 (kick 1.2/1.3) or later models of Amiga (A600/A1200/ or on any model) that was able to sit in RAM after the Amiga had been switched off. So these viruses would use the clock battery as power, and sit in RAM. I doubt that they could use the clock chip itself, as it's doubtful it had any programmable RAM, but I'm ready to be corrected (as I haven't read the technical specs of that chip). So on re-powering the Amiga the virus was re-emerge from RAM etc.

I doubt this ever happened and it was just virus-fear-, stories to sell print, slightly topical in the age of Covid19 , so did the Amiga ever need metaphorical hand gel, face masks and 2-meters?

[Jope]

No, there never was a clock virus and the main DRAM memory itself evaporates in about 30 seconds after power is removed.

[zipper]

No, there is no room for a virus. On my Amigas a little over 10 seconds Ctrl-A-A down was enough to clean up the memory.

[roondar]

The 30 second DRAM reminds me of something that happened on my C64 a couple of times: turn of the computer, wait a while to try to empty memory. Turn it back on and... You're still in the game or it crashes straight away with some random garbage on screen. Dunno why it happened, but I distinctly remember needing to wait up to a minute on more than one occasion to get my C64 working again.

On my A500 I do remember at least one occurrence of turning the machine off and then on again with very little pause in between (turned it off by accident) and the game was still there

[Jope]

I was really scared as a kid when I couldn't get rid of a reset killer in some Amiga demo or game.. It just showed a copper rainbow on the screen. Couldn't imagine the memory would hold data for so long so I thought my computer broke. :-)

[Nightshft]

The battery on accelerators (f.e. A500,A600,A1200) AFAIK will power the RealTimeClock Chip only. No DRam. Can't check the schematics for the internal clockport now but I can't imagine it would power any DRAM, which also would draw _much_ more current (just think that dram chips get hot when active) and thus drain the battery quite soon.
I can imagine the legend originates from memory not erased after a soft-reset or short power cycle.
Like for roondar turning of the C64 for only a second ("plop"-"plop") would sometimes work but sometimes result in a non-correctly-starting system (especially with the Action Cartridge plugged in) and a second/longer power cycle (5-10 secs always were enough).
Tell this practice somebody that grew up with modern pcs: "After using excel just save and push the reset button"