RE: Memory access (and floating-point correction)

[Lionel Pinkhard <lionelp@worldonline.co.za>]

Well, if I remember correctly, Motorola processors you the 'big endian'
format, the same as networks do, it would be something like this then:

	1 2 3 4

Pretty simple :-), but I don't know, I've never programmed one before.

Ciao,

Lionel

P.s. Doesn't anybody know how to access memory about 1MB? PLEASE :-)

On Thu, 7 Sep 2000, Kevin Wolfskill wrote:

> This is how they are laid out on an Intel processor (or its clones), but
> I'll bet that it is reversed on Motorola (68K) processors and I have no clue
> how the RISC processors like a G4 does its memory layout.
> 
> BTW - If noone every explained what cast does (or if they did, I missed it),
> 'casting' is data type conversion or specification (i.e. I have some data
> value in a unsigned short and I need it in a signed long, then the system
> does a 'cast').  At other times, if I have a pointer to something, I can
> cast the type of pointer when I access it, instead of at declaration time.
> A good example is a void *, which does not have a declared type, it is a
> 'raw' pointer.  By casting it at run time, I can change what the system
> thinks points to.  Does that make sense?  Probably not.
> 
> Kevin Wolfskill
> JADE Solutions
> Office US   (303) 448-1019 ext. 23
> Fax US      (303) 449-1548
> Kevin.Wolfskill@jadesolutions.com
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> 
> -----Original Message-----
> From: Lionel Pinkhard [mailto:lionelp@worldonline.co.za]
> Sent: Wednesday, September 06, 2000 4:35 PM
> To: gameprogrammer@gameprogrammer.com
> Subject: Memory access (and floating-point correction)
> 
> 
> Hi,
> 
> Firsty, a correction:
> 
> In my previous e-mail, I mentioned that floats are laid out like this:
> 
> 	2 1 4 3
> 
> Sorry, I was thinking of two different values, and it's better explained
> like this:
> 
> 	4 3 2 1
> 
> Everything's just reversed!
> 
> Okay, now for another problem:
> 
> Since the segment registers can only take a single word (Am I correct?),
> what would I do if I wanted to access memory above FFFF:FFFF? Let's say I
> wanted to access a value at 8507F:015A (just a random address), what would
> I do? The following code would be invalid, wouldn't it?
> 
> 	mov ax, 8507fh	; value too big for AX register
> 	mov es, ax	; value too big for ES register
> 	mov si, 15ah
> 	mov ax, byte ptr es:[si]
> 
> I think this explains my problem, can somebody help me out a bit?
> 	
> Ciao,
> 
> Lionel
> 
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