Re: [steem] Processors
- From: "Sven Karlsson" <svenka@xxxxxxxxx>
- To: <steem@xxxxxxxxxxxxx>
- Date: Wed, 21 Aug 2002 12:56:23 +0200
Hi All,
>being used (24-bit or 32-bit addresses, that would have to be checked
>everywhere).
Well, one feature I would very much like to see is support for Alt-RAM aka
TT-RAM aka Fast-RAM, i.e., the RAM which first appeared on the TT. The
TT-RAM is usually located at $01000000 and can be up to 1GB large on the TT
IIRC although it could go all the way up to $ffff0000 unless of course one
would like to emulate the VME slot. :-) Quite a few applications would
benefit from this actually. The ST hardware, i.e., the blitter, shifter,
ASCI/floppy DMA and so on cannot access the Alt-RAM. On the TT only the CPU
and the SCSI DMA chip could access the Alt-RAM.
This means of course that addresses need to be in some cases treated as
32-bit. A simple check for Alt-RAM accesses would be (in pseudo C-code):
if ((address>0x01000000) && (address<=Alt_ram_top))
{
/* access Alt-RAM */
}
else
{
address&=0x00ffffff;
/* access ST-RAM */
}
One can do this even more efficently of course.
Quite a lot of emulators can have up to 14Meg of ST-RAM, i.e., all the way
up to the STE's ROM. I would very much like to see support for this in steem
too.
Steem itself would only need to provide the memory so to speek as it is
straight forward to write applications for the auto folder that makes TOS
aware of the extra memory.
Third, it is space in the memory map on the STE (and onward) to have 1
megabyte of ROM. This is something I would like to see implemented as I
sometimes use steem for Fenix development. In fact, I would like to be able
to write to the ROM area too. The ROM shouldn't be writable by default of
course but it would be rather helpful if one could do as on flashROMs and
poke a sequence of well defined magic numbers into some imaginary hardware
registers to write a block of the rom or even individual bytes.
I'm prepared to help out implementing these features if needed.
Oh and by the way. What happened to the support for extended resolutions?
Did I miss something?
Best regards
Sven
--
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