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<!doctype html public "-//W3C//DTD HTML 3.2//EN"><html><head><title>Processor differences</title><meta http-equiv="content-type" content="text/html; charset=ISO-8859-1" /><meta http-equiv="content-language" content="en" /><meta name="resource-type" content="document"><meta name="copyright" content="This document copyright 2001 by Richard Murray. Use for non-profit and education purposes explicitly granted."><meta name="author" content="Richard Murray"><meta name="rating" content="general"></head><!-- /assembler/diff.html --><!-- --><!-- (C) Copyright 2001 Richard Murray --><!-- Designed by Richard Murray --><!-- rmurray@heyrick.co.uk --><!-- --><body bgcolor="#f0f0f0" text="#000000" link="#0022dd" vlink="#002288"><table border = "0" width="100%"> <tr> <td align=center width=100> <img src="arm3.gif" width=79 height=78 align = middle> </td> <td> <h1 align="center"><font color="#800080">Processor<br>differences</font></h1> </td> <td align=center width=100> <img src="arm3.gif" width=79 height=78 align = middle> </td></table><p> <p>This assembler programming site deals with the older ARM processors - the ARM 2 and the ARM 3.Well written code should work on later ARM processors, including the StrongARM.<p><ul> <li> ARM 2<br> The processor within the first RISC OS machines. For a brief time the ARM 2 also powered Arthur; but in the words of <i>STEPS</i>, that one is Better Best Forgotten. :-)</ul><p><ul> <li> Next came the ARM 3<br> This processor greatly boosted the behaviour of RISC OS due to a 4K cache.<br> An extra opcode was added, <code>SWP</code> which swaps between registers and memory.<br> Additionally, co-processor register 15 is used to communicate with the processor for things such as reading its version number.</ul><p><ul> <li> ARM 250<br> This was created for the A30x0 series. The actual chip contains the entire ARM chipset in one package (MEMC, VIDC, IOC, and ARM).<br> The ARM within this package is an ARM 250. It is a version of the ARM 3 without the co-processor register or the cache. It was designed to be cheap, the A30x0 series being to the Archimedes like the Electron was to the BBC micro.</ul><p>To determine which processor you have, you need to conduct a few tests:<br><pre> Does it understand SWP? If not, it is an ARM 2 Does it understand CP15 instructions? If not, it is an ARM 250. It is an ARM 3.</pre>This method will probably fail on later processors. I do not have data on how to identifyprocessors later than the ARM 3.<br>Of course, you can make some assumptions about the processor based on the OS:<ul> <li> If the ARM3Support module is present, an ARM 3 processor is in use...<br> <code>Set Arm3$Present Yes<br> RMEnsure ARM3Support 0.00 Set ARM3$Present No</code></ul><p>Here is some code to determine the processor type:<pre>REM Processor typeREMREM by Richard Murray 26th April 1999REM Updated 07/03/2001 so it won't kill 32-bit systems.REMREM Downloaded from: http://www.heyrick.co.uk/assembler/DIM code% 256FOR loop% = 0 TO 2 STEP 2 P% = code% [ OPT loop% STMFD R13!, {R1-R12, R14} ; Preserve registers MOV R0, #1 ; Set up a handler for ADR R1, unknown_instruction ; unknown instructions MOV R2, #0 MOV R3, #0 SWI "OS_ChangeEnvironment" SWI "OS_EnterOS" ; Enter SVC mode MOV R0, #2 \ Test for ARM 250 or better. ADR R2, safe_word ; Make R2 point somewhere safe EQUD &E1021091 ; "SWP R1, R1, [R2]" MOV R0, #250 \ Test for ARM 3. CMP R0, #250 ; Compare R0 with 250. EQUD &EE101F10 ; "MRCEQ CP15, 0, R1, C0, C0" MOV R0, #3 TSTP PC, #&F0000000 ; Return to USR mode. MOV R0, R0 LDMFD R13!, {R1-R12, PC} ; Restore registers and exit. .unknown_instruction ADDS PC, R14, #4 ; Upon unknown instruction, skip ; PC on beyond the MOV instruction. .safe_word EQUD 0 ]NEXTa% = USR(code%)CASE a% OF WHEN 2 : PRINT "Running on an ARM 2" WHEN 250 : PRINT "Running on an ARM 250" WHEN 3 : PRINT "Running on an ARM 3"OTHERWISE : PRINT "Running on unknown processor (reply = "+STR$(a%)+")"ENDCASEEND</pre><div align = right><a href="sw/proctype.basic"><i>Download example: proctype.basic</i></a></div><p>This software has only been tested on an ARM 3 processor.<p><hr size = "3"><a href="index.html#03">Return to assembler index</a><hr size = "3"><address>Copyright © 2001 Richard Murray</address></body></html>⌨️ 快捷键说明
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