@hwnd%

[Ric]

I now have my basic terrain rendering program working in BBCSDL32. Thankyou Richard. Starting to convert to BBCSDL64 has thrown up quite a few errors, so ill start with the first.

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 3522 DIM code%% NOTEND AND 2047, code%% (2048*40)-1
 3523 DIM ]^O% 2048, ]^L% -1
 3524 ]^P% = code%%
 3525 FOR I% = 0 TO 2 STEP 2
 3526
 3527   [
 3528   opt I%
 3529
 3530   .float4_to_8
 3531
 3532   fld              DWORD [float4]

Not sure about the DIM statements and what they do, but it syntax errors at line 3532.

[Richard Russell]

it syntax errors at line 3532.

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 3532   fld              DWORD [float4]

I'm no expert in 64-bit assembly language, but my understanding is that the memory operand can't be an absolute address (pointer), because it would require 8 bytes; very few instructions can take an 8-byte absolute address for the same reason. What you have to use instead is a relative address, which needs only four bytes - the same number as the absolute address would in 32-bit code:

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 3532   fld              DWORD [rel float4]

I discussed earlier in the thread the technique of using relative pointers rather than absolute ones, to keep the size as 32-bits, and this is an example of the CPU itself adopting the same strategy.