>If you measure the area increment in an Alpha 21064 or a Mips R4000 for a
>64-bit integer data path vs a 32-bit integer data path (floating point is
>64-bit in any case), you will see that the area increment is less than 10%.
>So it's not possible to build two 32-bit (equivalent performance/
>functionality) chips for the silicon area (=cost) of a 64-bit chip.
Maybe true. But for a user, should he buy one $2000 21064 chip or another
two $1000 CY7C601!?
If he chooses the first, he can advert that the 64-bit CPU could cover
all the 32-bit operations. But when this single 64-bit CPU crashed, then
send him to hell.
Certainly, when you using the 150MHz 21064, you might get the performance
to 200 MIPS. But could I beat such beast by 2 low-performance CPUs?
Quote:>The size of the integer data path (and virtual address) has little to no
>relationship to the bus architecture, bus bandwidth, memory bandwidth,
>or anything else on the list.
I think it is obvious, the *data path* has little to do with the bus
architecture. But what I concern *is not* the comparison between the
*single 64-bit* to *single 32-bit*. All I want to know is about the
feasibility of two or more CPUs to challenge one high performance
CPU. Just when you implement CPU pool on your machine, could you say
that the bus architecture really does not have any relation to CPUs?
(I would like to rectify, since I am confused why so many *buses*
>UNIX on the R4000, and VMS on Alpha, and NT on both, are today 32-bit
>operating systems with 32-bit user environments (although this may not
>necessarily be true in the future).
I believe, tuning the 32-bit OS to 64-bit environment would not induce
much difficulty. However, tell me how to do when you try to port the
single CPU OS to multiprocessor OS. Sun Micro had shipped some MP
platforms, asking them if the OS should need to recode and redesing
if necessary (multithread in SunOS 5.0 ?!).
You can make only the kernel knows well about the under layer h/w arch.,
but if could also explore the parallelism in the compiler level.
So I believe, that the best compiler should reflect the actual computer
architectuer even it can shield such detail from the users.
Someone says that if you need 64-bit addresses or arith. quantities of
64-bits then there's no question. But since 64-bit operations can be
also perform by the 32-bit algorithms, I would wonder how really
advantage that singe 64-bit CPU would obtain when compares two 32-bit