Scor­pio News

  

October–December 1987 – Volume 1. Issue 4











Page 9 of 55











SEPARATE USER/SUPERVISOR MODES

System mode is used for all operating system code, race debugged). “Any tanigreasions

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256 BYTE CACHE

‘This 1 found was an extremely weful feature which connderably speeded up the running of the program when it” wer in a short repeating loop. The cache i transparent to the user, il til “oni asrucons tod Gata fom the ma memory daring any fe, tine the proser ight ‘means that 3c processor i ready to process ks ex tastruction a takes Wt from the cache rather than main memory ths ctting down On the numberof external bus scores.

‘The cache may be enabled for data, instructions or both, on bus 5 and 6 of the “Cache ‘On restt the cache i eaubled for instructions oaly.. The. PCACHE ‘eorre validates the 256 ‘byte on-chip cache, “Instead of using. the fast memory

SEPARATE BLOCKS FOR PROGRAM, DATA & OPERATING SYSTEM

1 have found when programming that due to the size and amount of variables I use that the data

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THE INTERRUPT/TRAP VECTOR TABLE

The UT vector table consists of pairs of Master status register and Program counter words, one pir foreach interrupt or trap 04ree. ‘The CPU contains an additional register, the “InterruptTrap Vector Table Pointer’ I This

contains the top 12 bits of the physical address of the contents of the “Interrupt/Trap Vector ‘Table “Any interrupt or trap, finds the address ofits service routine fom this abe,


This is an OCR’d version of the scanned page and likely contains recognition errors.











Page 9 of 55