Mem Alloc Bootblock

[LeCaravage]

Hi there,

I would like to alloc mem in order to copy data there. It's a bootblock code as the rest of the program is trackloaded after that from disk to fast mem.
Need approx 100Kbytes in Fast (or Fake Fast) memory.
Can someone explain me how it works ? May be a code sample in asm ?
A method that should work in all Amigas (OCS,ECS,AGA) would be great.
Also, a simple method, please

Thanks,

[Galahad/FLT]

move.l #size_of_data,d0
move.l #$10004,d1
move.l 4.w,a6
jsr -$c6(a6)

If successful, pointer to the allocated memory space will be passed as a longword in D0, if not succesful, D0 = 0

However, I wouldn't only allocate just fast memory, because if you want your program to work on 1meg chip ram machines, they are less likely to have the fast ram located at $c00000

I typically do this, I try and allocate absolute memory, because from bootup, we can be pretty sure that the middle of the second half of chip ram from booting up the disk is free hence checking for the $c0000 memory range.

And likewise, checking in the middle of fake fast ram $c40000 is a pretty safe bet.

You obviously don't have to use those memory addresses afterwards, you're simply checking that memory type is available, obviously once you know it is, then $80000 would be the start of the second half of 512K chip ram in a 1 meg chip ram machine, and $c00000 is the base address of slow fast ram expansion.

move.l 4.w,a6
move.l #$c0000,a1
jsr -$216(a6)
tst.l d0
beq.s not_1meg_chip

move.l #$c40000,a1
jsr -$216(a6)
tst.l d0
beq.s not_fake_fast

[LeCaravage]

Thanks for your fast and detailled reply.

Indeed, going for absolut memory allocs seems to be the best choice.

[Photon]

As long as you will not exit the bootblock to CLI/WB, this is OK for checking what kind of machine you're running on. But even if you don't exit, if you later try to allocate memory, it will now be fragmented (if you use AbsAllocs and don't free it).

Obviously don't use the slowmem (fake fast) check to assume that there's no fastmem in the machine, because lots of Amigas have fastmem without slowmem, and they could still have just the 512K chipmem.

[Old_Bob]

Is there no handy system variable tucked away somewhere that has the amount of Chip & Fast RAM that we can read to get an easy answer?

B

[LeCaravage]

@Photon: I won't exit bootblock as the rest of the trackloaded program will turn system off. I have an Amiga 500 KS1.3 + FakeFast (1,8Mb) but I'd like to make the program ECS,AGA compatible.
About the NoFakeFastMem & YesTrueFastMem case, adding to Galahad's code this paragraph will be ok ? :

move.l #$240000,a1
jsr -$216(a6)
tst.l d0
beq.s not_realfastmem

[StingRay]

Originally Posted by Old_Bob

Is there no handy system variable tucked away somewhere that has the amount of Chip & Fast RAM that we can read to get an easy answer?

B

For max. available CHIP you can use Exec's MaxLocMem, for fast mem AvailMem() does the trick.

[Galahad/FLT]

Originally Posted by LeCaravage

@Photon: I won't exit bootblock as the rest of the trackloaded program will turn system off. I have an Amiga 500 KS1.3 + FakeFast (1,8Mb) but I'd like to make the program ECS,AGA compatible.
About the NoFakeFastMem & YesTrueFastMem case, adding to Galahad's code this paragraph will be ok ? :

move.l #$240000,a1
jsr -$216(a6)
tst.l d0
beq.s not_realfastmem

Yes, as true fast mem is at $200000 for that machine

Obviously if you were not binning the system right from the start, using allocabs isn't a good idea, but from the bootblock, we can be certain that most of memory is clear and the check will work.

[Photon]

Originally Posted by LeCaravage

@Photon: I won't exit bootblock as the rest of the trackloaded program will turn system off. I have an Amiga 500 KS1.3 + FakeFast (1,8Mb) but I'd like to make the program ECS,AGA compatible.
About the NoFakeFastMem & YesTrueFastMem case, adding to Galahad's code this paragraph will be ok ? :

move.l #$240000,a1
jsr -$216(a6)
tst.l d0
beq.s not_realfastmem

Real fastmem could basically start anywhere >=$200000. Unless you're doing something very special with it, you shouldn't care whether fastmem is fake or real.

Lots of setups have fastmem at $1000000, $40000000, and even $c80000 (with no RAM at $c00000-$c80000). So you shouldn't rely on fixed addresses.

Originally Posted by StingRay

For max. available CHIP you can use Exec's MaxLocMem, for fast mem AvailMem() does the trick.

This will give you available chipmem and fastmem to make decisions.

If you find you need an actual start address for chipmem/fastmem, you can allocate the largest chunk and take the addresses.

If you need the system on for library calls, you're done. Just pass the pointers to the rest of the code. If not, it's safe to round them off to the nearest lower or equal 512K boundary.

Chipmem always starts at address $0. But some bytes are required for the different CPUs. I use $100.w as the start address for the loader.

[Galahad/FLT]

Originally Posted by Photon

Real fastmem could basically start anywhere >=$200000. Unless you're doing something very special with it, you shouldn't care whether fastmem is fake or real.

Lots of setups have fastmem at $1000000, $40000000, and even $c80000 (with no RAM at $c00000-$c80000). So you shouldn't rely on fixed addresses.


This will give you available chipmem and fastmem to make decisions.

If you find you need an actual start address for chipmem/fastmem, you can allocate the largest chunk and take the addresses.

If you need the system on for library calls, you're done. Just pass the pointers to the rest of the code. If not, it's safe to round them off to the nearest lower or equal 512K boundary.

Chipmem always start at address $0. But some bytes are required for the different CPUs. I use $100.w as the start address for the loader.

I use $c0.... but, The Bitmap Brothers are more dope than me, they use $80

[Apollo]

trap #0 ?

[ross]

Originally Posted by Apollo

trap #0 ?

Surely they are careful not to use it if writing code from $80

[ross]

And stepping through ExecBase->MemList?
You can have a real view of memory mapping and select the best.

Bye
ross