Re: AS255: UW SCSI, sound, video, kernel

[Jay.Estabrook@digital.com]

>>> Eric Jorgensen said:
> Alex Winbow wrote:
> 
> >         To bring this back to the Alpha, doesn't x86 kernel support for a
> > scsi driver imply Alpha (and SPARC and MIPS and ...) support?
> 
> 	Ehh, not hardly!
> 
> 	IA32 = little endian, 32 bit words
> 
> 	Alpha = big endian, 64 bit words

Uh, half right; IIRC, Alpha is actually capable of either-endian (like
MIPS), however, Linux-Alpha is little endian, as is Digital UNIX, NT, and
VMS.
 
> 	So, no. Not all linux code works on all systems. XFree86 is a good
> example. How many servers work on Alpha as compared to x86?

A lot of the cause for the lack of servers on Alpha is because of x86
assembler code in the lowest level of the drivers. Not rocket science to
port, but there has to be a *need*. For most of the drivers, there has been
no (perceived) need, primarily because when Alpha Linux started, it was with
"legacy" machines, ie ones that were already equipped with video controllers
that they were originally sold with. Thus there was a quite small group of
controllers which it was deemed important to support at the beginning; S3
and Mach64 were the first VGAs (we sold many boxes with those installed),
while TGA was supported because of the hordes of UDB/MULTIA that appeared.
Fortunately, this group has grown quite a bit over time to include the newer
popular VGAs, including ones that we don't even sell (eg. Imagine 128).

This is not to say that simply porting the x86 assembler to Alpha is all
that is needed. There are some other "features" of the Alpha architecture
that must be considered when attempting to write such code; take a look at
the register accessing in the SVGA Millennium sources, for example, or for
a real gross-out, the S3 code to run on JENSEN... ;-}

--Jay++

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Jay A Estabrook                            Alpha Motherboards - LINUX Project
Compaq Computer Corporation - SHR3-2/R28   (508) 841-3241 or (DTN) 237-3241
334 South Street, Shrewsbury, MA 01545     Jay.Estabrook@digital.com
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