[clug] assembly performance

[Adrian Blake]

Martin Pool wrote:
> On  8 Jun 2005, Adrian Blake <A.Blake at physics.usyd.edu.au> wrote:
> 
>>This is a question about microprocessor architecture.
>>
>>10 or 20 years ago assembly code addressed physical hardware, registers 
>>ALUs and alike with an underlying simple microcode.
>>
>>This has changed. but to what extent?
>>
>>Does assembly code still operate on the physical hardware or is it  a 
>>virtual machine with one or more layers of microcode? 
> 
> 
> I think any modern large processor has some degree of microcoding.
> Whether that makes it a virtual machine or not rather depends on which
> definition you choose to use.
> 

In assembly code on the modern micros are we addressing and manipulating 
the silicon or just talking to a virtual processor ?
> 
>>What are the performance penalties if any?
> 
> 
> Penalties compared to what?  One could presumably always make chips
> faster by adding more gates and/or spending more time on low-level
> design rather than using microcode, but at what price?
> 
If assembly code operates the silicon the performance is dependent upon 
the skills of the assembly coder. But if the assembly code is 
interpreted by a lower level code that simulates a virtual machine then 
the performance can vary and the user is at the mercy of the microcoder.


-- 
Adrian Blake
Molonglo Radio Observatory
University of Sydney
1152 Hoskinstown Rd
Bungendore 2621
ph. 02 62382262  mobile 0407 232 978

http://www.molonglo.physics.usyd.edu.au