By: Andi Kleen (ak-rwt.delete@this.muc.de), November 15, 2006 4:24 am
Room: Moderated Discussions
rwessel (robertwessel@yahoo.com) on 11/14/06 wrote:
>If they did that today, certainly. But what about ten years from now? Given that
>x87 is almost unused by 64 bit applications,
SYSV x86-64 ABI uses it for long double. I can't
really estimate how much long double is used in
the field. But "almost unused" may be too strong.
>the only real users will be 32 bit
>apps. At a certain point it may become reasonable to depreciate it fully.
I remember Gelsinger once got asked in a interview
about the A20 gate (which is still there) and if it would be ever remove. He answer was (paraphrased) that the incremental cost of keeping it was low and the risk of not selling a new product well because of missing compatability
was much higher. I suspect that will apply to x87
for a long time too.
>Note that AMD did exactly that with v86 mode in x86-64 - it goes away completely
>in long mode. If an OS vendor wanted to continue to support 16-bit real-mode applications,
>they'd have to write an emulator. MS, for example, has chosen not to,
Their way to support it is VirtualPC. Linux's is qemu.
Compatibility is still there.
> and has dropped
>16 bit protected mode support as well in x86-64 bit versions of Windows (although
>there's not a hardware reason for that).
The funny thing is that 16bit Windows programs still
work under x86-64 Linux in Wine. Linux is more compatible
to Windows than Win64 @)
-Andi
>If they did that today, certainly. But what about ten years from now? Given that
>x87 is almost unused by 64 bit applications,
SYSV x86-64 ABI uses it for long double. I can't
really estimate how much long double is used in
the field. But "almost unused" may be too strong.
>the only real users will be 32 bit
>apps. At a certain point it may become reasonable to depreciate it fully.
I remember Gelsinger once got asked in a interview
about the A20 gate (which is still there) and if it would be ever remove. He answer was (paraphrased) that the incremental cost of keeping it was low and the risk of not selling a new product well because of missing compatability
was much higher. I suspect that will apply to x87
for a long time too.
>Note that AMD did exactly that with v86 mode in x86-64 - it goes away completely
>in long mode. If an OS vendor wanted to continue to support 16-bit real-mode applications,
>they'd have to write an emulator. MS, for example, has chosen not to,
Their way to support it is VirtualPC. Linux's is qemu.
Compatibility is still there.
> and has dropped
>16 bit protected mode support as well in x86-64 bit versions of Windows (although
>there's not a hardware reason for that).
The funny thing is that 16bit Windows programs still
work under x86-64 Linux in Wine. Linux is more compatible
to Windows than Win64 @)
-Andi
