[Simh] performance issues vax / simh / openvms / itanium

[gérard Calliet]

Hello,

I have a VAX emulated with simh compiled and running on OpenVMS 8.4-1H1 
(vsi) Itanium i4. The software used does only heavy cpu tasks (Ada cross 
compiler).
The performance is surprinsigly bad: about 4 times lower than then VAX 
station 4000-90. A compilation batch which was taking 7mn of CPU takes 
on the emulator 24mn of CPU.
The host Itanium uses 1 core at 100%, and not a lot of page faults, 100 
dio /s which I think is for the emulated clock.

(I use the same (back/image) system disk as of the initial hardware VAX. 
I have verified I use all the 512m of memory, there are not a lot of 
page fault on the VAX.)


I don't understand why it is so bad. I thought about some special things 
on C compilation, but which?
Any suggestions?

Thanks,
Gérard Calliet


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