English Amiga Board


Go Back   English Amiga Board > Coders > Coders. Asm / Hardware

 
 
Thread Tools
Old 13 March 2018, 17:02   #21
hitchhikr
Registered User

 
Join Date: Jun 2008
Location: somewhere
Posts: 372
That's what i made to check if there's any memory above the 512k of chip, it needs a valid execbase structure (you can typically cram this at the start of your bootblock):

Code:
MaxLocMem equ 62
MemList equ 322

 ; check if we have enough memory available
 move.l  4.w,a6
 move.l  MaxLocMem(a6),d1 ; top of chip memory
 move.l  MemList(a6),d2
 cmp.l   #$80000,d2
 blt.b   top_chip
 move.l  d2,4.w           ; this is the new extra mem start address
 bra.b   init_work
top_chip:
 cmp.l   #$80000,d1       ; only 512k of chip and nothing else
 ble.w   goto_512k_failure
 move.l  #$80000,4.w      ; at least 1mb chip is the new extra mem start address
init_work:
hitchhikr is offline  
Old 13 March 2018, 17:30   #22
ross
Omnia fert aetas

ross's Avatar
 
Join Date: Mar 2017
Location: Crossing the Rubicon
Age: 48
Posts: 1,079
Quote:
Originally Posted by NorthWay View Post
And it could also be that chipram is 1M or 2M so don't fall over if you don't find another chunk.
My snippet take care of it
ross is offline  
Old 13 March 2018, 22:33   #23
jotd
Cat freak
jotd's Avatar
 
Join Date: Dec 2004
Location: FRANCE
Age: 46
Posts: 2,483
a lot of games (Team 17, Rich Aplin) do this AllocMem stuff + masking to get hold of the memory locations. Some also wrongly assume $C00000 (supercars II) or write into $200000 to see if there's some memory here (wrong as well, as AGA mirrors chip to 0: lotus II)...

As long as you're not planning to revive the system afterwards, do what you want, take advantage of a machine with physical memory layed out for you
jotd is offline  
Old 13 March 2018, 23:20   #24
alpine9000
Registered User

 
Join Date: Mar 2016
Location: Australia
Posts: 595
Quote:
Originally Posted by jotd View Post
a lot of games (Team 17, Rich Aplin) do this AllocMem stuff + masking to get hold of the memory locations. Some also wrongly assume $C00000 (supercars II) or write into $200000 to see if there's some memory here (wrong as well, as AGA mirrors chip to 0: lotus II)...

As long as you're not planning to revive the system afterwards, do what you want, take advantage of a machine with physical memory layed out for you
No the system can only be revived with a reboot

I have a fully system friendly version of the program if people want to keep the OS running in the background, but this requires more ram than 1mb.
alpine9000 is online now  
Old 14 March 2018, 07:20   #25
jotd
Cat freak
jotd's Avatar
 
Join Date: Dec 2004
Location: FRANCE
Age: 46
Posts: 2,483
ah a reboot always works

[ Show youtube player ]

jotd is offline  
Old 14 March 2018, 08:21   #26
dissident
Registered User

 
Join Date: Sep 2015
Location: Germany
Posts: 153
Quote:
Originally Posted by alpine9000 View Post
Cool thanks, yeah this version is system takeover, so no need to waste ram for dead OS data structures.

Also how low can I go with chip ram? The size of the vector table? 256?
Well, RSI in their Megademo used $000c0 - $7ffff. It covers all interrupt autovectors and also the trap #0-15 instruction vectors. And since everyone knows this famous demo this method works on most OCS machines.
Attached Thumbnails
Click image for larger version

Name:	RSI-Megademo.jpg
Views:	36
Size:	52.0 KB
ID:	57269  
dissident is offline  
Old 14 March 2018, 10:20   #27
Galahad/FLT
Going nowhere

Galahad/FLT's Avatar
 
Join Date: Oct 2001
Location: United Kingdom
Age: 45
Posts: 6,978
Quote:
Originally Posted by hooverphonique View Post
And also make sure, you're not overwriting your own running code which may or may not be at some arbitrary address chosen by the os, depending on how you bootstrap
I get around this as I have always done by having a very small bootup code, which I let EXEC allocate and relocate to wherever it likes, and then I then transfer that boot code to address $C0, and I either run it from that low address, or if its going to cause problems for other code, I then transfer it again to another address higher in memory.

But I do all my memory checking/processor checking and anything else that needs EXEC or AmigaDOS before I do the transfer to low mem.
Galahad/FLT is offline  
Old 18 March 2018, 22:33   #28
Photon
Moderator
Photon's Avatar
 
Join Date: Nov 2004
Location: Hult / Sweden
Posts: 4,568
Just Alloc the largest chunk of the two memory types and add intelligence.

For Fastmem you shouldn't take liberties, there could a mapped ROM there or anything else resident that the user needs for his accelerator. If the chunk is smaller than 512K, you could fairly safely assume that you could grab anything below it, but not the area above it, then again expansions could load hw drivers into low fastmem before you boot, so.

For chip memory, more things are known so that again, you could grab the memory below it but not above it, unless of course you check the two stack pointers first and they both point to fastmem. It's your choice if you want to be that close to overwrite vectors near $200000 from a slight bug in your code, like a bob overlapping the bottom right corner of a screen buffer.

Most memory will be free at boot anyway, so Exec's Alloc will give you a very good idea of the total size of the hardware memory available to you, and you can show an information box if it's too little for your spec.

I.e. it's needless to be greedy when your stuff can work on so many configs without the greed. For example, my choice for low chip start is $200, which should give enough wiggle room for current and future accelerator zero page storage. When would you need the extra $100 or $140 bytes? If the answer is, "in cases so rare they're not even worth considering", then be sensible not greedy.
Photon is offline  
Old 05 April 2018, 12:41   #29
alpine9000
Registered User

 
Join Date: Mar 2016
Location: Australia
Posts: 595
Quote:
Originally Posted by Toni Wilen View Post
Also make sure you don't accidentally overwrite supervisor stack (which is usually located at the end of $c00000 RAM if system does not have any real fast RAM), or move it to better place.
So I discovered that kickstart 2.04 with 512chip and 512slow puts the supervisor stack pointer in low slow ram, so I had to move that to a known good location (back to the end of my allocated ram).

Is this a safe way to set the ISP ? Seems to work ok, the very next thing that happens is the OS is turned off.

Code:
.setisp:
        lea     .setit(pc),a5
	jsr     -30(a6)               ; SuperVisor()
.setit:
       	move.l  d0,sp                 ; d0 is new ISP location
	andi.w  #$dfff,sr             ; Back to user mode
alpine9000 is online now  
Old 05 April 2018, 14:57   #30
ross
Omnia fert aetas

ross's Avatar
 
Join Date: Mar 2017
Location: Crossing the Rubicon
Age: 48
Posts: 1,079
At the end you need a system takeover so why not just stay in supervisor mode?

Anyway with Supervisor() you do not have to touch SP if you want to return to usermode (RTE at the end is due).

Code:
.setisp:
        lea     .setit(pc),a5
	jsr     -30(a6)            ; Supervisor()
        bra     main

.setit:
       	movec   vbr,d0             ; some supervisor stuff
	rte                        ; back to user mode
Logically you can also make a new stack frame in a new location with a proper usermode return
(pushing SR/RTS and setting USP -> move.l a0,USP).

Different thing if you think to use SuperState()/UserState().

Last edited by ross; 05 April 2018 at 15:15. Reason: example
ross is offline  
Old 05 April 2018, 23:10   #31
alpine9000
Registered User

 
Join Date: Mar 2016
Location: Australia
Posts: 595
Quote:
Originally Posted by ross View Post
At the end you need a system takeover so why not just stay in supervisor mode?

Anyway with Supervisor() you do not have to touch SP if you want to return to usermode (RTE at the end is due).

Code:
.setisp:
        lea     .setit(pc),a5
	jsr     -30(a6)            ; Supervisor()
        bra     main

.setit:
       	movec   vbr,d0             ; some supervisor stuff
	rte                        ; back to user mode
Logically you can also make a new stack frame in a new location with a proper usermode return
(pushing SR/RTS and setting USP -> move.l a0,USP).

Different thing if you think to use SuperState()/UserState().
Because my usermode stack is changed a few lines later and I was concerned about potentially the stack frame being incompatible between processors I figured it was easier not to bother returning to user mode with rte.

I use the rte method when I get the VBR.
alpine9000 is online now  
Old 06 April 2018, 10:44   #32
hooverphonique
ex. demoscener "Bigmama"
 
Join Date: Jun 2012
Location: Fyn / Denmark
Posts: 786
Quote:
Originally Posted by alpine9000 View Post
Because my usermode stack is changed a few lines later and I was concerned about potentially the stack frame being incompatible between processors I figured it was easier not to bother returning to user mode with rte.

I use the rte method when I get the VBR.
And you're right in doing so, because the stack frames ARE different between processors. Note that you need to do move.l d0, USP when changing the user mode sp from supervisor mode. Also note that e.g. 68040 has a separate interrupt stack pointer:
Code:
Stack Pointers
ISP Supervisor/Interrupt Stack Pointer
MSP Supervisor/Master Stack Pointer
SP  Active Stack Pointer
SSP Supervisor (Master or Interrupt) Stack Pointer
USP User Stack Pointer
hooverphonique is offline  
Old 06 April 2018, 10:54   #33
alpine9000
Registered User

 
Join Date: Mar 2016
Location: Australia
Posts: 595
Quote:
Originally Posted by hooverphonique View Post
And you're right in doing so, because the stack frames ARE different between processors. Note that you need to do move.l d0, USP when changing the user mode sp from supervisor mode. Also note that e.g. 68040 has a separate interrupt stack pointer:
Code:
Stack Pointers
ISP Supervisor/Interrupt Stack Pointer
MSP Supervisor/Master Stack Pointer
SP  Active Stack Pointer
SSP Supervisor (Master or Interrupt) Stack Pointer
USP User Stack Pointer
Ah so I need to detect 040 and set both privileged stack pointers? What about 060?

I currently set the USP in user mode.
alpine9000 is online now  
Old 06 April 2018, 11:18   #34
Toni Wilen
WinUAE developer
 
Join Date: Aug 2001
Location: Hämeenlinna/Finland
Age: 43
Posts: 21,786
No need to care about MSP/ISP difference if you never manually set M-bit in SR.
Toni Wilen is offline  
Old 06 April 2018, 11:22   #35
alpine9000
Registered User

 
Join Date: Mar 2016
Location: Australia
Posts: 595
Quote:
Originally Posted by Toni Wilen View Post
No need to care about MSP/ISP difference if you never manually set M-bit in SR.
Great! Many thanks for everyone’s help!

I seem to finally be able to use every last byte of my trapdoor ram expansion
alpine9000 is online now  
Old 06 April 2018, 21:50   #36
hooverphonique
ex. demoscener "Bigmama"
 
Join Date: Jun 2012
Location: Fyn / Denmark
Posts: 786
Quote:
Originally Posted by Toni Wilen View Post
No need to care about MSP/ISP difference if you never manually set M-bit in SR.
so the master supervisor mode is only used when the M-bit is set, and we know that LVOSupervisor() doesn't use master supervisor mode?
hooverphonique is offline  
Old 06 April 2018, 22:55   #37
ross
Omnia fert aetas

ross's Avatar
 
Join Date: Mar 2017
Location: Crossing the Rubicon
Age: 48
Posts: 1,079
Quote:
Originally Posted by hooverphonique View Post
so the master supervisor mode is only used when the M-bit is set, and we know that LVOSupervisor() doesn't use master supervisor mode?
Yes.
ross is offline  
Old 06 April 2018, 23:05   #38
ross
Omnia fert aetas

ross's Avatar
 
Join Date: Mar 2017
Location: Crossing the Rubicon
Age: 48
Posts: 1,079
Quote:
Originally Posted by hooverphonique View Post
And you're right in doing so, because the stack frames ARE different between processors.
You are right, but i think that code similar to this can work in every situation:

Code:
	move.w	#$4000,$dff09a
	movea.l	$4.w,a6
	lea	super(pc),a5
	jsr	-30(a6)
	
	
super	lea	$80000,sp       ; set to your top stack memory address
	lea	-$400(sp),a0    ; too little? make it bigger :)
        clr.w   -(sp)           ; short format (010+)
	pea	main(pc)
	clr.w	-(sp)           ; SR usermode
	move	a0,USP
	rte
	
main	bra.b	main
Untested

EDIT: tested in WinUAE from bare 68k to 060.

All is working properly:
000 -> SSP to $7fffe, USP to $7fc00, main in usermode (2 bytes lost, not a problem the misalign)
010+ -> SSP to $80000, USP to $7fc00, main in usermode (stack aligned for 020+)

Last edited by ross; 07 April 2018 at 00:18. Reason: test
ross is offline  
Old 07 April 2018, 00:34   #39
alpine9000
Registered User

 
Join Date: Mar 2016
Location: Australia
Posts: 595
Quote:
Originally Posted by ross View Post
You are right, but i think that code similar to this can work in every situation:

Code:
	move.w	#$4000,$dff09a
	movea.l	$4.w,a6
	lea	super(pc),a5
	jsr	-30(a6)
	
	
super	lea	$80000,sp       ; set to your top stack memory address
	lea	-$400(sp),a0    ; too little? make it bigger :)
        clr.w   -(sp)           ; short format (010+)
	pea	main(pc)
	clr.w	-(sp)           ; SR usermode
	move	a0,USP
	rte
	
main	bra.b	main
Untested

EDIT: tested in WinUAE from bare 68k to 060.

All is working properly:
000 -> SSP to $7fffe, USP to $7fc00, main in usermode (2 bytes lost, not a problem the misalign)
010+ -> SSP to $80000, USP to $7fc00, main in usermode (stack aligned for 020+)
What’s the advantage of doing this rather than just clearing the S bit?
alpine9000 is online now  
Old 07 April 2018, 00:49   #40
ross
Omnia fert aetas

ross's Avatar
 
Join Date: Mar 2017
Location: Crossing the Rubicon
Age: 48
Posts: 1,079
Post

Quote:
Originally Posted by alpine9000 View Post
What’s the advantage of doing this rather than just clearing the S bit?
All-in-one solution to be in a definite state (both user and super stack set, user mode on)
and a (dumb) way to use RTE without fear of different stack frames.

Well, only an example, but actually never used.
Like I've said for a system take-over I use S=1 and I never return to user mode.

But you are right, my code is overbloated , better:

Code:
super	lea	$80000,sp       ; set to your top stack memory address
	lea	-$400(sp),a0    ; too little? make it bigger :)
	move	a0,USP
        andi    #$dfff,sr
	
main

Last edited by ross; 07 April 2018 at 01:41.
ross is offline  
 


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Similar Threads
Thread Thread Starter Forum Replies Last Post
AmiDEVcpp: Allocating gfxdata in chip mem tolkien Coders. C/C++ 9 22 April 2013 20:21
Listing files, loading files and allocating all available chip ram. h0ffman Coders. System 16 04 April 2013 21:24
Problem allocating some memory CmdrVimes Coders. General 4 03 September 2010 23:23
Allocating Fast RAM as Chip? Fingerlickin_B support.Hardware 22 20 November 2008 22:15
A600 Not allocating full 1mb FOL support.Hardware 24 18 October 2008 13:02

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +2. The time now is 13:26.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2018, vBulletin Solutions Inc.
Page generated in 0.11301 seconds with 16 queries