assembly - Loading program from RAM in 8086 -

-

the 8086 using 16-bit instruction ram addresses hold 8-bit how cpu load programms ram ? load 1 address , checks if instruction needs 1/2/3 bytes (e.g. moving immediate register 8/16 bit) , executes operation or getting wrong 1 ram 'space' 16-bit big ?

many instructions multi-byte, , yes means span 2 or more addresses.

iirc, 8086's memory bus 16-bit, can load 16 bits (two adjacent addresses) in single operation. you're confusing byte-addressable memory bus width.

does load 1 address , checks if instruction needs 1/2/3 bytes (e.g. moving immediate register 8/16 bit)

it continually fetches instruction bytes 6-byte buffer (2 bytes @ time, because it's 16-bit cpu 16-bit busses). buffer large enough hold largest allowed 8086 instruction (excluding prefixes, might decoded separately, idk). when it's done executing previous instruction, looks @ buffer. see link below better description, tries decode buffer whole instruction. if hits end of fetch buffer before finding end of instruction, waits until next fetch cycle has completed , tries again.

see also: 8086 cpu architecture, first hit "8086 code fetch". confirms fetch , execute overlap, it's pipelined in basic way.

tl:dr: fetches buffer until has whole instruction decode. shifts bytes front of buffer, because they're part of next instruction.

i've read instruction-fetch bottleneck 8086, optimizing code-size outweighed pretty else.

a pipelined cpu wouldn't have wait execution of previous instruction finish started on decoding. modern cpus have much higher bandwidth code-fetch, have queue of decoded instructions ready go (except when branches mess up.) see http://agner.org/optimize/, , other links in tag wiki.

also, common instructions single byte, push r16.


Comments

Post a Comment

Popular posts from this blog

mysql - Dreamhost PyCharm Django Python 3 Launching a Site -

-
i'm new python/django , created simple django website using pycharm. site works fine running on computer, i'm lost when comes taking site onto host (dreamhost). i'm able upload files correct directories fine, , believe made correct changes database on mysql. i'm not sure go there though. right now, page shows files rather site. direction appreciated. much! you should not run django application using python manage.py runserver on production. how run application on django depends on server (apache, nginx) want use for apache - https://docs.djangoproject.com/en/1.10/howto/deployment/wsgi/modwsgi/ for nginx - https://www.digitalocean.com/community/tutorials/how-to-serve-django-applications-with-uwsgi-and-nginx-on-ubuntu-14-04 the mysql database should, of course, exist , have correct credentials. or, if choose use sqlite, file should accessible, readable , writable www-user (may different depending on linux distributive)
Read more

java - Sending SMS with SMSLib and Web Services -

-
i have made rest web service send smss using hsdpa usb modem. using smslib in java send smss. every time web service invoked, create gateway start service, send message, stop service , remove gateway. takes 20 seconds each message. found starting service takes lot of time. part of code use send smss service.getinstance().addgateway(gateway); service.getinstance().startservice(); outboundmessage msg = new outboundmessage(phonenumber, message); if (service.getinstance().sendmessage(msg)) { result = "message sent successfully!!"; } else { result = "could not send message."; } service.getinstance().stopservice(); service.getinstance().removegateway(gateway);//remove gateway is there way can start service once if not started , use send message when ever web service invoked? why dont group messages , send in 1 go? service.getinstance().sendmessages(messa...
Read more

java - How to resolve The method toString() in the type Object is not applicable for the arguments (InputStream) -

-
i'm trying read json file local machine. @path("/") public class jsonparsing { file f = new file("file.json"); if (f.exists()){ inputstream = new fileinputstream("file.json"); string jsontxt = ioutils.tostring(is); system.out.println(jsontxt); jsonobject json = new jsonobject(jsontxt); string = json.getstring("1000"); system.out.println(a); } } but i'm getting error in tostring() method. possible read .txt file containing json object local machine? if possible, how done? firstly: whenever ask question- add imports well. secondly: yes possible read .txt file containing json object. steps: 1. add maven dependency in pom.xml - <dependency> <groupid>com.googlecode.json-simple</groupid> <artifactid>json-simple</artifactid> <version>1.1.1</version> </dependency> or add jar of dependency. 2.import...
Read more