15-347 Spring '98, Final Exam Official solution 

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PROBLEM 1.

A. $31
B. -1
C. E7FFFFFF

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PROBLEM 2.

No.  When \verb@p == 0@, the {\tt ldl} would attempt to read from
virtual address 0.  This is never a legal address in an Alpha
processor.

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PROBLEM 3.

A - E: miss / hit / hit / miss / miss

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PROBLEM 4.

A - D: miss 16 / hit 0 / miss 32 / miss 32

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PROBLEM 5.

A. 1/2
B. (a) 12.5% (b) 25% (c) 25%

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PROBLEM 6.

A. Error.  Cannot have TLB valid and page table entry invalid
B. Error.  Aliasing---VPN 05 also maps to PPN 16.  
C. OK.     Not valid, so translation does not matter
D. OK.     TLB and page table both map to PPN 11.

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PROBLEM 7.

A. When exp = 1 will turn number into denorm.  Maintains same
   exponent weight but eliminates implied 1.  Value is +- (x - 2^-126)
B. Always wrong.  Wraps +-0 to +-infinity.  Others to NaN
C. Always wrong.  Maps to +-2^127
D. Always wrong.  Maps to +-(1.sig)*2^127,

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PROBLEM 8.

struct s1: t 0 4 | y 4 4 | l 8 4  | h 16 8 |
struct s2: k 0 8 | m 8 8 | r 16 8 | c 24 8 |
struct s3: a 0 8 | o 8 8 |
union  u1: e 0 4 | d 0 8 |

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PROBLEM 9.

p1: c->r->a->y
p2: c->o->c->k->e
p3: a->m->d->a->h->l

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PROBLEM 10.
CYCLE              0 1 2  3  4 5 6 7 8 9 0  1 2 3 4       
addq $31, 0x8, $1: F D E$1 M W
cmoveq $1, $1, $2:   F D $1E M W
beq $2, target:        F  D  E M W
stq $1, 0x0($31):         F  D E 
stq $1, 0x8($31):            F D
stq $1, 0x10($31):             F
target:                          
ldq $1, 0x8($1):                 F D E M$1 W
stq $1,0x10($1):                   F D D $1E M W
addq $1, $2, $3:                     F F  D  E M W
call_pal halt:                            F  D E M W   

A. BRK
B. call_pal halt
C. c14

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PROBLEM 11.
CYCLE               0 1 2 3 4 5 6 7 8 9
addq $30, 0x8, $31: F D E M W
beq $31, target:      F D E M W
ldq $1, -0x8($31):      F D E
call_pal halt:            F D
target:
stq $31, 0x4($31):          F F D E M W
call_pal cflush                 F D E M
addq $30, $30, $31:               F D E
call_pal halt                       F D


A. ADR (address 0x4 is unaligned)
B. stq $31, 0x4($31)
C. c9

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PROBLEM 12.

A. 1000 * p / (10 + 0.025p)
B. p >= 100

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PROBLEM 13.

A. h * (10 + 0.025p)
B. h <= 8

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PROBLEM 14.

A. 60%
B. 60%

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PROBLEM 15.

A. 80%
B. 80%

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PROBLEM 16.

Small line size: Not exploiting spatial locality of reference
Large line size: Getting false sharing
Medium: Exploiting spatial locality without false sharing

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PROBLEM 17.

9.6 X 10^9 B/sec

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PROBLEM 18.

Notation:

{ ix, iy | iw, iz } means either:
  ix, iy, iw, iz, or  iw, iz, ix, iy


A. { i1, i2 | i4, i5 }, { i3 | i6 } 
B. { i1 | i4 }, { i2, i3 | i5, i6 } or
   { i1 | i4 }, { i2 | i5 } | { i3, i6 } 
C. i4, i5, { i1 | i6 }, i2, i3  

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