[hatari-devel] Fwd: Falcon memory

[Laurent Sallafranque]

Hi,

I've finished to make some tests with the memory.

It seems that only bits 1, 4 and 5 are used by the TOS on boot to 
determine the amount of memory.
Thomas, I'll base the final patch on your doc, as it seems to be the 
most complete and the most realistic explanation.

Just before I commit, do you prefer me to only include 1 Meg, 4 megs and 
14 Megs or should I add also 512 Ko, 2 Mo and 8 Mo ? (As it seems 
possible with TOS 4.04 to have all these memory size) ?


Here is  the result of my tests :

$ffff8006 MM-BB --B-


Bits 5, 4, 1 (BBB)

00 = 512 Ko
02 = 1024
10 = 2048
12 = 4096
20 = 8192
22 = 14366
30 = Illegal
32 = Illegal


Here is an extract of the TOS booting sequence :

//Get Falcon memory
MOVE.W $ffff8006,D0

LSR.W #$00000008,D0
LSR.B #$00000001,D0
MOVE.B D0,D1

//Get bit 1 of register $ffff8206.b
AND.B #$01,D1

//Get bits 4 and 5 of register $ffff8206.b
LSR.B #$00000002,D0
AND.B #$06,D0
OR.B D0,D1

//Compute memory size
MOVE.L #$00080000,D0
ASL.L D1,D0
CMP.B #$05,D1
BNE.B #$00000006 == $00E00164 (T)

// ?
MOVE.L D0,D5
LEA.L $00000400,A4
MOVE.L D5,D4
SUB.L A4,D4
LSR.L #$00000008,D4
SUB.L #$00000001,D4
LEA.L $00000200,A5
MOVE.L #$00000000,D0
MOVEA.L D0,A0
MOVE.L #$00000000,D1
MOVEA.L D1,A1
MOVE.L #$00000000,D2
MOVEA.L D2,A2
MOVE.L #$00000000,D3
MOVEA.L D3,A3

// Loop on memory test
LEA.L (A4, $0100) == $00000500,A4
MOVEM.L D0-D3/A0-A3,-(A4)
MOVEM.L D0-D3/A0-A3,-(A4)
MOVEM.L D0-D3/A0-A3,-(A4)
MOVEM.L D0-D3/A0-A3,-(A4)
MOVEM.L D0-D3/A0-A3,-(A4)
MOVEM.L D0-D3/A0-A3,-(A4)
MOVEM.L D0-D3/A0-A3,-(A4)
MOVEM.L D0-D3/A0-A3,-(A4)
ADDA.L A5,A4
DBF .W D4,#$ffdc == $00E0018A (F)

....
This loops seems to repeat for each slice of memory.

Regards,

Laurent Sallafranque
Groupe Arkea
RPCAS Informatique
1 rue Louis Lichou
29480 Le Relecq Kerhuon
Tél : 02 98 00 20 76


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