Re: [steem] Processors
- From: "Steem Authors" <steem@xxxxxxx>
- To: "Steem Discussion" <steem@xxxxxxxxxxxxx>
- Date: Wed, 28 Aug 2002 22:36:58 +0100
Hi Sven,
> 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.
I really can't see this being that useful, surely if a program uses FastRAM
it will be likely to want to use other TT features. Also some ST programs
would access addresses with the high byte set to something assuming it would
be masked out, this could stop them working. Even though one "if else"
doesn't seem to be much, when it is being executed up to 2 million times a
second it can make a difference in speed, and we wouldn't want to risk it
for an option that might only be useful for 1 or 2 programs.
> 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.
That is very possible without major changes, but again there are so few
programs that would make use of that amount of RAM.
> 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.
That again is possible, I will think about it.
> Oh and by the way. What happened to the support for extended resolutions?
> Did I miss something?
They are in the Machine Config dialog, in the monitor drop-down.
Thanks for all your suggestions,
Russ
--
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