Cray CRAY-1 - Active Exchange Package; Exchange Sequence

Syndrome (S) - The eight syndrome bits used in detecting the error are
returned in
bits 2 through 9 of the first word of the exchange package.
Refer to section 5 for additional information.
Read mode (R) - This field indicates the read mode in progress when the
error occurred and consists of bits 10 and 11 of the first word of the
exchange package. These bits assume the following values:
00 Scalar
01 I/O
10 Vector
11 Instruction fetch
Read address (RAB) - The RAB field contains the address at which the error
occurred. Bits 12 through 15 (B) of the first word of the exchange package
contain bits 2
3
through 2° of the address and may be considered as the bank
address; bits 0 through 15 (RA) of the second word of the exchange package
contain bits 2
19
through 24 of the address.
Active
exchange package
An active exchange package is an exchange package which is currently
residing in the
computer operating registers. The interval of time in
which the exchange package is active is called the execution interval for
the
exchange package and also for the program with which it is associated.
The execution interval begins with an exchange sequence in which the
subject
exchange package moves from memory to the operating registers.
The exp.cution interval ends as the exchange package moves back to
memory in a subsequent exchange sequence.
EXCHANGE SEQUENCE
The exchange sequence is the vehicle for moving an inactive exchange
package from memory into the operating registers and at the same time
moving the currently active exchange package from the operating registers
back into memory. This swapping operation is done in a fixed sequence
when all computational activity associated with the currently active
2240004
3-42
E