[clug] assembly performance

Adrian Blake A.Blake at physics.usyd.edu.au
Fri Jun 10 03:13:22 GMT 2005

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


More information about the linux mailing list