Author: Christophe Theron
Date: 21:26:19 02/15/00
Go up one level in this thread
On February 15, 2000 at 22:45:28, Tom Kerrigan wrote:
>On February 15, 2000 at 20:42:43, Ricardo Gibert wrote:
>
>>MIPS VR4121 is a 64 bit CPU according to NEC. Look at
>>http://www.nec.com/Semiconductors/categories/679/981008.html
>
>You're right... Hmmm... I wonder what the "64 bit" measures. Maybe memory
>interface? Because it seems pretty silly to have a full-blown 64-bit embedded
>processor, when your desktop machine is still 32-bit...
>
>-Tom
Wait a minute. The VR4121 processor claims pin-to-pin compatibility with the
VR4111. And the VR4111 is a "false 64 bits" processor. Operations can be done on
64 bits internally, but the data bus size is 16 or 32 bits. That is, there is a
serious bottleneck between the processor and the memory when it comes to 64 bits
values.
I'm not even sure that this processor really supports clean 64 bits operations.
All the docs I have mention 16 and 32 bits long instructions. How do you perform
a move immediate with a 64 bits value if your instruction length is limited to
32 bits?
And don't count on the 8Kb internal L1 data cache to store all the data needed
by Crafty...
A bitboard program looks like a poor choice for this architecture.
Christophe
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