Question about Slow Mem

[Brick Nash]

I noticed today that I had 512KB of SlowMem set in WinUAE. Don't know why I missed it, but there it is. My real Amiga doesn't have any SlowMem, but I noticed that when I removed it in WinUAE I also lose about 200KB of Graphics Mem.

Just Wondering what's happening there?

I'm wondering if the SlowMem is being used by the OS which is freeing up ChipMem when it's available?

Thanks.

[Ernst Blofeld]

The OS will generally only use chip memory for stuff that the custom chips need to access. If fast memory is available it will prefer that, as it's, well, faster, but if no fast memory is available, then it will use slow memory. If no fast or slow memory is used, it will use chip memory. Remember that fast memory is faster because it's only accessed by the CPU, chip memory can be accessed by the CPU and the custom chips, and slow memory shares the same set up as chip memory, which is why it can become chip memory if you have the right versions of the custom chips.

Maybe someone can explain it simpler than that, but it shouldn't be more complex.

Edit: Unless you're using an OS version that doesn't know the difference between slow and fast memory? Is there such a thing?

[Brick Nash]

Thanks for the reply. That clears it up.

There's no fast memory available, so it probably just uses the slow when it's there. Bit of a bastard, because as I said my real Amiga 600 doesn't have any Fast or Slow, so I lost 200K of Chipmem that I thought I had.

Will just need to learn to trash the OS I guess.

[thomas]

The OS does not distinct Fast RAM and Slow RAM. It assigns certain attributes to memory areas and Slow is not one of them.

During allocation you can specify which attributes you need. For example Chip RAM or DMA cappable. The most common allocation uses "just any". In this case the OS chooses by priority. The highest priority memory is used first.

Chip and Slow RAM are recognised by the OS and the priorities it assigns are known. Real Fast RAM needs to be added by the expansion's firmware. As Chip and Slow priorities are known, the expansion usually chooses a higher priority so that Fast RAM is preferred.

In the age of Kick 1.2 there were utilities called FastMemFirst or SlowMemLast. You can guess what they did: they changed the priorities and thus the order in which the OS chooses memory during an allocation.

[derSammler]

Isn't "slow ram" a term made up by people anyway? Pretty sure "Ranger memory" was the correct term.

[Ernst Blofeld]

Originally Posted by thomas

The OS does not distinct Fast RAM and Slow RAM. It assigns certain attributes to memory areas and Slow is not one of them.

During allocation you can specify which attributes you need. For example Chip RAM or DMA cappable. The most common allocation uses "just any". In this case the OS chooses by priority. The highest priority memory is used first.

Chip and Slow RAM are recognised by the OS and the priorities it assigns are known. Real Fast RAM needs to be added by the expansion's firmware. As Chip and Slow priorities are known, the expansion usually chooses a higher priority so that Fast RAM is preferred.

In the age of Kick 1.2 there were utilities called FastMemFirst or SlowMemLast. You can guess what they did: they changed the priorities and thus the order in which the OS chooses memory during an allocation.

Words.

The OS priorities which memory to use first.

Older OS versions were less good at this.

There.

We all have bike sheds to paint.

[Brick Nash]

Ok, thanks for the replies.

Just wanted to know where that Graphics mem vanished to.

I had 1972864 Graphics Mem +318992 Other with 512KB SlowMem enabled in WinUae, but 1760208 Graphics Mem and 0 Other with it removed.

[Galahad/FLT]

Originally Posted by Brick Nash

Ok, thanks for the replies.

Just wanted to know where that Graphics mem vanished to.

I had 1972864 Graphics Mem +318992 Other with 512KB SlowMem enabled in WinUae, but 1760208 Graphics Mem and 0 Other with it removed.

If slow/fast is available, AmigaDOS will use it for execbase pointer structure, libraries, and anything else that doesn't specifically need chip ram to run.

So of course if you don't have any slow/fast ram, all those AmigaDOS elements and libraries and memory lists must now be stored in chip ram.

[Brick Nash]

Originally Posted by Galahad/FLT

If slow/fast is available, AmigaDOS will use it for execbase pointer structure, libraries, and anything else that doesn't specifically need chip ram to run.

So of course if you don't have any slow/fast ram, all those AmigaDOS elements and libraries and memory lists must now be stored in chip ram.

That's what I thought. Thanks for the clarification.

So it looks like I'll need to ditch using the OS to get some memory back. I'll likely need to start another thread on just how to do that, as I've no idea how.

I only use it to allocate memory and load from disk, so maybe it won't be too bad.

[redblade]

Do all the Graphics, Sound Data take up more than 1MB CHIP on your 2MB A600 when loaded?

[Photon]

Slowmem is a term that got adopted for the internal memory expansion in the A500 specifically. It's as fast as chipmem, which on a 7MHz 68000 is 30-33% slower than (sidecar expansion) memory for large memory operations.

Like Galahad says, for any Kickstart some memory is needed for OS memory structures. All Amigas feel better with some fastmem, even in the form of slowmem, because these structures can end up there instead of ending up in the precious chipmem, which really only should have structures the chipset needs to access with DMA.

If this is for a floppy executable file release, you could try Ross's bootblock or Space Boot to maximize chipmem left at prompt. If it fits then, you won't have to recode.

[Brick Nash]

Originally Posted by redblade

Do all the Graphics, Sound Data take up more than 1MB CHIP on your 2MB A600 when loaded?

Yes. The assets are sizeable as is (even split into horizontal strips), but they also need flipped versions and masks. There's music and sound FX too.

Originally Posted by Photon

Slowmem is a term that got adopted for the internal memory expansion in the A500 specifically. It's as fast as chipmem, which on a 7MHz 68000 is 30-33% slower than (sidecar expansion) memory for large memory operations.

Like Galahad says, for any Kickstart some memory is needed for OS memory structures. All Amigas feel better with some fastmem, even in the form of slowmem, because these structures can end up there instead of ending up in the precious chipmem, which really only should have structures the chipset needs to access with DMA.

If this is for a floppy executable file release, you could try Ross's bootblock or Space Boot to maximize chipmem left at prompt. If it fits then, you won't have to recode.

It's for a game. Runs from floppies/adfs at the moment.

Not having to recode would be a blessing. I don't even think I'd need the full 200K back. Just a bit.