>More obscure.  It has to do with how memory accesses to bytes are
>handled on the Alpha architecture.  They're not very quick, because
>the Alpha wants to do all memory access in 32bit chunks.

"Quick" is in the eye of the beholder.  Yes, the Alpha tended to access data in 32 bit "chunks" to get it into the registers.   Being a RISC processor it was not as rich in data access on a byte level.   On the other hand other CISC processors also accessed data on a 32-bit level, just that their instruction sets used microcode to make it look like they were only accessing a byte.   The trade off was in executing multiple RISC instructions to one microcoded CISC instruction.

Would this bother a kernel developer writing a couple of lines of assembly language down at the very lowest level of the kernel....probably.

On the other hand for years Linus talked about the Alpha as the best architecture chip he knew, so it could not have been too bad.

md

On Thu, Feb 4, 2021 at 5:29 PM John Stoffel <john@stoffel.org> wrote:
>>>>> "Keith" == Keith Wright <kwright@keithdiane.us> writes:

Keith> John Stoffel via WLUG <wlug@lists.wlug.org> writes:
>> I recall, it's mostly the memory ordering around byte accesses that
>> are the problem. 

Keith> Are you saying that the Big Endian vs Little Endian flame war
Keith> actually had consequences in the Real World?

It did, and still does.  MIPS processors can be BE or LE (Big/Little
Endian) depending on how you configure them as I understand, though
this is more the smaller micro-controllers used in embedded stuff.

I personally play around with ATTiny85 and ATTiny84 MCUs when I get a
chance.  Slowly looking at STM8 and STM32 stuff as well.  And of
course the Arduino AVR stuff. 

Keith> Or something even more obscure?

More obscure.  It has to do with how memory accesses to bytes are
handled on the Alpha architecture.  They're not very quick, because
the Alpha wants to do all memory access in 32bit chunks.

I honestly don't recall all the full details.  You can find info in
the LKML (Linux Kernel Mailing List) which discuss this over the
years.  Looks for Posts by Linus Torvalds which also mention Alpha.
Interesting reading.