1447:
1433:
System/370-XA changed the page table entry format to support 19 bits of page frame address; pages are 4 KB in 370-XA, so combining a 19-bit page frame address with a 12-bit offset within the page produces a 31-bit physical address. Channel command words can be in one of two formats, with format 0
1375:, Branch and Save Register, was part of the instruction set of the 360/67, which was the only System/360 model to allow addresses longer than 24 bits. These instructions were maintained, but were modified and extended for 31-bit addressing.
1378:
Additional instructions in support of allowing calls between 24-bit-addressing and 31-bit-addressing code include two new register-register call/return instructions which also effect an addressing mode change,
1350:
Input from key initial Model 67 sites, which had debated the alternatives during the initial system design period, and had recommended 31 bits (instead of the 32-bit design that was ultimately chosen at the
1395:
allow 24-bit calls to 31-bit (and return to 24-bit), 31-bit calls to 24-bit (and return to 31-bit), 24-bit calls to 24-bit (and return to 24-bit) and 31-bit calls to 31-bit (and return to 31-bit).
1328:
This was addressed by adding an addressing mode bit to the
Program Status Word controlling whether the program runs in 24-bit mode, in which the top eight bits of virtual addresses are ignored, or
1325:, Load Address, explicitly cleared the top eight bits of the address being placed in a register. If the 24-bit limit were to be removed, this would create migration problems for existing software.
1422:, where 0 indicates that the current mode is not saved (the program is leaving the subroutine, anyway), and a return to the caller at the address and mode specified in register 14 is to be taken.
1383:, Branch and Save and Set Mode, the 24/31 bit version of a call where the linkage address including the mode is saved and a branch is taken to an address in a possibly different mode, and
1336:
The desire to retain the high-order bit as a "control or escape bit." In particular, the standard subroutine calling convention marked the final parameter word by setting its high bit.
1739:
1363:, Branch and Link Register, store certain status information, the instruction length code, the condition code and the program mask, in the top byte of the return address. A
1387:, Branch and Set Mode, the 24/31 bit version of a return, where the return is directly to the previously saved linkage address and in its previous mode. Taken together,
1410:, where the linkage address and mode are saved in register 14, and a branch is taken to the subroutine address and mode specified in register 15. Somewhat similarly to
1648:
1734:
1309:
were 32 bits wide, the machine did 32-bit arithmetic operations, and addresses were always stored in 32-bit words, so the architecture was considered
1347:
that treated their arguments as signed numbers when doing comparisons (and which was said to be the reason TSS used 31-bit addressing on the Model 67).
176:
1355:
Certain machine instructions in this 31-bit addressing mode alter the addressing mode bit. For example, the original subroutine call instructions
1332:
mode, in which only the uppermost bit of virtual addresses are ignored. Several reasons were given for the choice of 31 bits instead of 32 bits:
1724:
1671:
304:
1695:
1430:
System/370 initially supported only 24-bit physical addresses; the extended real address feature extended this to 26-bit addresses.
236:
1262:
IBM documentation numbers the bits from high order to low order; the most significant (leftmost) bit is designated as bit number 0.
1539:
1596:
1434:
being the System/370 format, with a 24-bit data address, and format 1 being an additional format, with a 31-bit data address.
1729:
1274:
169:
125:
1744:
1477:
System/370-XA introduced a channel subsystem that performed I/O queuing previously done by the operating system.
268:
1306:
318:
66:
1298:
162:
1285:
architecture to support 31-bit virtual and physical addresses, and includes a redesigned I/O architecture.
104:
231:
46:
311:
1317:
addressing. Much of System/360's and System/370's large installed code base relied on a 24-bit
1685:, for extensive examples of the use of BAS, BASR, BASSM and BSM, in particular, pp. 29–30.
1609:... the high order bit in the last fullword must be set to one to indicate the end of the list.
1634:
1501:, the high order bit is always guaranteed to be set to 0, thereby indicating 24-bit mode, for
1578:
1329:
1314:
1310:
1318:
273:
255:
51:
1625:
1282:
328:
294:
150:
130:
99:
84:
61:
56:
1446:
1718:
94:
31:
1569:
A. Padegs (May 1983). "System/370 Extended
Architecture: design considerations".
89:
1302:
1294:
281:
1367:, Branch and Save, instruction was added to allow 31-bit return addresses.
1278:
78:
74:
70:
1582:
1339:
Interaction between 32-bit addresses and two loop control instructions,
17:
1673:
MVS/Extended
Architecture System Programming Library: 31-Bit Addressing
1601:
z/OS MVS Programming: Authorized
Assembler Services Reference, Volume 4
145:
140:
1313:, but the machines ignored the top 8 bits of the address resulting in
1564:
1562:
1560:
1558:
109:
1704:
1680:
1656:
1604:
1548:
1441:
198:
1541:
IBM System/370 Extended
Architecture Principles of Operation
1359:, Branch and Link, and its register-register equivalent,
1080:
External Mask; subject to external subclass mask in CR0
1458:
1321:; In particular, a heavily used machine instruction,
1506:
1502:
1498:
1494:
1419:
1415:
1414:(the 24-bit-only form of an unconditional return),
1411:
1407:
1403:
1399:
1392:
1388:
1384:
1380:
1372:
1368:
1364:
1360:
1356:
1344:
1340:
1322:
327:
317:
310:
300:
290:
280:
267:
254:
242:
230:
212:
204:
194:
1627:VM and the VM community, past present, and future
1493:Because the instruction length code is 00b for a
1707:. September 1987. p. 3-26. A22-7000-10.
1653:z/OS MVS Programming: Assembler Services Guide
1534:
1532:
1530:
1528:
1526:
170:
8:
189:
1740:Products and services discontinued in 1988
1179:
1021:
177:
163:
26:
1571:IBM Journal of Research & Development
1069:I/O Mask; subject to channel mask in CR2
1619:
1617:
1371:, and its register-register equivalent,
733:
541:
444:
347:
1522:
1486:
117:
38:
29:
1735:Computer-related introductions in 1983
1697:IBM System/370 Principles of Operation
1649:"Using the BASSM and BSM instructions"
338:
188:
7:
1597:"WAIT — Wait for one or more events"
90:eServer zSeries (900, 800; 990, 890)
1277:introduced by IBM in 1983 with the
1402:(the 24-bit-only form of a call),
1024:S/370-XA EC mode PSW abbreviations
25:
339:
1445:
105:zEnterprise System (z196, zEC12)
1:
1725:IBM System/360 mainframe line
543:Floating Point Registers 0-6
1683:. January 1984. GC28-1158-1.
1281:processors. It extends the
1275:instruction set architecture
458:See Principles of Operation
218:; 41 years ago
1761:
1551:. March 1983. SA22-7085-0.
1426:31-bit physical addressing
1020:
940:
930:
747:
649:
642:
560:
547:
457:
450:
360:
353:
110:IBM Z (z13, z14, z15, z16)
1307:general-purpose registers
1289:31-bit virtual addressing
806:
803:
782:
557:
1624:Varian, Melinda (1997).
1509:on XA and later systems.
1157:1=Secondary-space mode
446:Control Registers 0-15
361:Two's complement value
349:General Registers 0-15
1637:89 Sessions 9059-9061.
735:Extended Architecture
341:IBM S/370-XA registers
262:(2, 4 or 6 bytes long)
1703:(Eleventh ed.).
1199:Fixed-point overflow
1153:Address-Space Control
650:Mantissa (continued)
1251:Instruction Address
1155:0=primary-space mode
941:Instruction Address
276:, indexing, counting
1730:Computing platforms
1679:(Second ed.).
1583:10.1147/rd.273.0198
1577:(3). IBM: 198–205.
1305:architectures, the
1240:0=24 bit; 1=31 bit
1215:Exponent underflow
1184:
1120:Machine-check mask
1026:
744:
544:
447:
350:
343:
191:
1547:(First ed.).
1457:. You can help by
1180:
1022:
734:
542:
445:
348:
1497:and is 01b for a
1475:
1474:
1297:, other than the
1271:IBM System/370-XA
1268:
1267:
1259:
1258:
1255:
1254:
1227:
1226:
1207:Decimal overflow
728:
727:
536:
535:
439:
438:
337:
336:
263:
246:Register–Register
187:
186:
16:(Redirected from
1752:
1745:32-bit computers
1709:
1708:
1702:
1692:
1686:
1684:
1678:
1667:
1661:
1660:
1645:
1639:
1638:
1632:
1621:
1612:
1611:
1593:
1587:
1586:
1566:
1553:
1552:
1546:
1536:
1510:
1508:
1504:
1500:
1496:
1491:
1470:
1467:
1449:
1442:
1421:
1417:
1413:
1409:
1405:
1401:
1394:
1390:
1386:
1382:
1374:
1370:
1366:
1362:
1358:
1346:
1342:
1324:
1185:
1183:
1027:
1025:
745:
743:ontrol mode PSW
558:Biased exponent
545:
448:
351:
344:
261:
226:
224:
219:
192:
179:
172:
165:
27:
21:
1760:
1759:
1755:
1754:
1753:
1751:
1750:
1749:
1715:
1714:
1713:
1712:
1700:
1694:
1693:
1689:
1676:
1670:
1668:
1664:
1647:
1646:
1642:
1630:
1623:
1622:
1615:
1595:
1594:
1590:
1568:
1567:
1556:
1544:
1538:
1537:
1524:
1519:
1514:
1513:
1492:
1488:
1483:
1471:
1465:
1462:
1455:needs expansion
1440:
1428:
1319:logical address
1291:
1239:
1238:Addressing mode
1181:
1168:Condition Code
1156:
1154:
1023:
931:
808:
779:
774:
748:
643:
548:
451:
354:
319:General-purpose
249:
248:Register–Memory
247:
222:
220:
217:
183:
47:700/7000 series
23:
22:
15:
12:
11:
5:
1758:
1756:
1748:
1747:
1742:
1737:
1732:
1727:
1717:
1716:
1711:
1710:
1687:
1662:
1640:
1613:
1588:
1554:
1521:
1520:
1518:
1515:
1512:
1511:
1485:
1484:
1482:
1479:
1473:
1472:
1452:
1450:
1439:
1436:
1427:
1424:
1353:
1352:
1348:
1337:
1290:
1287:
1283:IBM System/370
1266:
1265:
1264:
1263:
1257:
1256:
1253:
1252:
1249:
1246:
1242:
1241:
1236:
1233:
1229:
1228:
1225:
1224:
1221:
1217:
1216:
1213:
1209:
1208:
1205:
1201:
1200:
1197:
1193:
1192:
1189:
1177:
1174:
1170:
1169:
1166:
1163:
1159:
1158:
1151:
1148:
1144:
1143:
1142:Problem state
1140:
1137:
1133:
1132:
1129:
1126:
1122:
1121:
1118:
1115:
1111:
1110:
1100:
1097:
1093:
1092:
1089:
1086:
1082:
1081:
1078:
1075:
1071:
1070:
1067:
1064:
1060:
1059:
1056:
1053:
1049:
1048:
1045:
1042:
1038:
1037:
1034:
1031:
1018:
1017:
1015:
1012:
1010:
1008:
1006:
1004:
1002:
1000:
998:
996:
994:
992:
990:
988:
986:
984:
982:
980:
978:
976:
974:
972:
970:
968:
966:
964:
962:
960:
958:
956:
954:
951:
948:
945:
944:
942:
939:
936:
933:
932:
928:
927:
925:
922:
920:
918:
916:
914:
912:
910:
907:
904:
902:
900:
897:
894:
891:
888:
885:
882:
879:
876:
873:
870:
868:
866:
863:
860:
857:
854:
851:
849:
846:
843:
840:
837:
836:
834:
831:
828:
825:
822:
819:
816:
813:
810:
805:
802:
799:
796:
793:
790:
787:
784:
781:
776:
771:
768:
765:
762:
759:
756:
753:
750:
749:
730:
729:
726:
725:
723:
720:
718:
716:
714:
712:
710:
708:
706:
704:
702:
700:
698:
696:
694:
692:
690:
688:
686:
684:
682:
680:
678:
676:
674:
672:
670:
668:
666:
664:
662:
660:
657:
654:
653:
651:
648:
645:
644:
640:
639:
637:
634:
632:
630:
628:
626:
624:
622:
620:
618:
616:
614:
612:
610:
608:
606:
604:
602:
600:
598:
596:
594:
592:
590:
587:
584:
582:
580:
578:
576:
574:
571:
568:
565:
564:
562:
559:
556:
553:
550:
549:
538:
537:
534:
533:
531:
528:
526:
524:
522:
520:
518:
516:
514:
512:
510:
508:
506:
504:
502:
500:
498:
496:
494:
492:
490:
488:
486:
484:
482:
480:
478:
476:
474:
472:
470:
468:
465:
462:
461:
459:
456:
453:
452:
441:
440:
437:
436:
434:
431:
429:
427:
425:
423:
421:
419:
417:
415:
413:
411:
409:
407:
405:
403:
401:
399:
397:
395:
393:
391:
389:
387:
385:
383:
381:
379:
377:
375:
373:
371:
368:
365:
364:
362:
359:
356:
355:
335:
334:
331:
329:Floating point
325:
324:
321:
315:
314:
308:
307:
302:
298:
297:
292:
288:
287:
284:
278:
277:
274:Condition code
271:
265:
264:
258:
252:
251:
244:
240:
239:
234:
228:
227:
214:
210:
209:
206:
202:
201:
196:
185:
184:
182:
181:
174:
167:
159:
156:
155:
154:
153:
151:z/Architecture
148:
143:
138:
133:
128:
120:
119:
115:
114:
113:
112:
107:
102:
97:
92:
87:
82:
64:
59:
54:
49:
41:
40:
36:
35:
34:, 1952–present
32:IBM mainframes
24:
14:
13:
10:
9:
6:
4:
3:
2:
1757:
1746:
1743:
1741:
1738:
1736:
1733:
1731:
1728:
1726:
1723:
1722:
1720:
1706:
1699:
1698:
1691:
1688:
1682:
1675:
1674:
1666:
1663:
1658:
1654:
1650:
1644:
1641:
1636:
1629:
1628:
1620:
1618:
1614:
1610:
1606:
1602:
1598:
1592:
1589:
1584:
1580:
1576:
1572:
1565:
1563:
1561:
1559:
1555:
1550:
1543:
1542:
1535:
1533:
1531:
1529:
1527:
1523:
1516:
1490:
1487:
1480:
1478:
1469:
1460:
1456:
1453:This section
1451:
1448:
1444:
1443:
1437:
1435:
1431:
1425:
1423:
1396:
1376:
1349:
1338:
1335:
1334:
1333:
1331:
1326:
1320:
1316:
1312:
1308:
1304:
1300:
1296:
1288:
1286:
1284:
1280:
1276:
1272:
1261:
1260:
1250:
1247:
1244:
1243:
1237:
1234:
1231:
1230:
1223:Significance
1222:
1219:
1218:
1214:
1211:
1210:
1206:
1203:
1202:
1198:
1195:
1194:
1190:
1187:
1186:
1178:
1175:
1172:
1171:
1167:
1164:
1161:
1160:
1152:
1149:
1146:
1145:
1141:
1138:
1135:
1134:
1130:
1127:
1124:
1123:
1119:
1116:
1113:
1112:
1108:
1104:
1101:
1098:
1095:
1094:
1090:
1087:
1084:
1083:
1079:
1076:
1073:
1072:
1068:
1065:
1062:
1061:
1057:
1054:
1051:
1050:
1046:
1043:
1040:
1039:
1035:
1032:
1029:
1028:
1019:
1016:
1013:
1011:
1009:
1007:
1005:
1003:
1001:
999:
997:
995:
993:
991:
989:
987:
985:
983:
981:
979:
977:
975:
973:
971:
969:
967:
965:
963:
961:
959:
957:
955:
952:
949:
947:
946:
943:
937:
935:
934:
929:
926:
923:
921:
919:
917:
915:
913:
911:
908:
905:
903:
901:
898:
895:
892:
889:
886:
883:
880:
877:
874:
871:
869:
867:
864:
861:
858:
855:
852:
850:
847:
844:
841:
839:
838:
835:
832:
829:
826:
823:
820:
817:
814:
811:
800:
797:
794:
791:
788:
785:
777:
772:
769:
766:
763:
760:
757:
754:
752:
751:
746:
742:
738:
732:
731:
724:
721:
719:
717:
715:
713:
711:
709:
707:
705:
703:
701:
699:
697:
695:
693:
691:
689:
687:
685:
683:
681:
679:
677:
675:
673:
671:
669:
667:
665:
663:
661:
658:
656:
655:
652:
647:
646:
641:
638:
635:
633:
631:
629:
627:
625:
623:
621:
619:
617:
615:
613:
611:
609:
607:
605:
603:
601:
599:
597:
595:
593:
591:
588:
585:
583:
581:
579:
577:
575:
572:
569:
567:
566:
563:
554:
552:
551:
546:
540:
539:
532:
529:
527:
525:
523:
521:
519:
517:
515:
513:
511:
509:
507:
505:
503:
501:
499:
497:
495:
493:
491:
489:
487:
485:
483:
481:
479:
477:
475:
473:
471:
469:
466:
464:
463:
460:
455:
454:
449:
443:
442:
435:
432:
430:
428:
426:
424:
422:
420:
418:
416:
414:
412:
410:
408:
406:
404:
402:
400:
398:
396:
394:
392:
390:
388:
386:
384:
382:
380:
378:
376:
374:
372:
369:
367:
366:
363:
358:
357:
352:
346:
345:
342:
332:
330:
326:
322:
320:
316:
313:
309:
306:
303:
299:
296:
293:
289:
285:
283:
279:
275:
272:
270:
266:
259:
257:
253:
250:Memory–Memory
245:
241:
238:
235:
233:
229:
215:
211:
207:
203:
200:
197:
193:
190:System/370-XA
180:
175:
173:
168:
166:
161:
160:
158:
157:
152:
149:
147:
144:
142:
139:
137:
134:
132:
129:
127:
124:
123:
122:
121:
116:
111:
108:
106:
103:
101:
98:
96:
93:
91:
88:
86:
83:
80:
76:
72:
68:
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37:
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28:
19:
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1626:
1608:
1600:
1591:
1574:
1570:
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1459:adding to it
1454:
1432:
1429:
1397:
1377:
1354:
1327:
1292:
1270:
1269:
1182:Program Mask
1109:ontrol mode
1106:
1102:
740:
736:
340:
135:
118:Architecture
1418:is used as
1408:BASSM 14,15
1406:is used as
1131:Wait state
291:Predecessor
67:30XX series
52:1400 series
39:Market name
30:History of
1719:Categories
1517:References
1400:BALR 14,15
1303:System/370
1295:System/360
295:System/370
282:Endianness
213:Introduced
131:System/370
126:System/360
100:System z10
85:System/390
62:System/370
57:System/360
1412:BCR 15,14
1058:DAT mode
1047:PER Mask
561:Mantissa
312:Registers
301:Successor
269:Branching
260:Variable
95:System z9
1466:May 2023
1420:BSM 0,14
1279:IBM 308X
1191:Meaning
1105:xtended
1091:PSW key
1036:Meaning
739:xtended
333:4 64-bit
256:Encoding
195:Designer
136:S/370-XA
18:S/370-XA
1293:In the
807:Program
305:ESA/370
221: (
146:ESA/390
141:ESA/370
1351:time).
1330:31-bit
1315:24-bit
1311:32-bit
1301:, and
1299:360/67
1273:is an
1245:33-63
1173:20-23
1162:18-19
1033:Field
232:Design
208:32-bit
1701:(PDF)
1677:(PDF)
1635:SHARE
1631:(PDF)
1545:(PDF)
1481:Notes
1404:BASSM
1398:Like
1389:BASSM
1381:BASSM
1085:8-11
1030:Bits
809:Mask
1669:See
1505:and
1503:BALR
1495:BALR
1391:and
1373:BASR
1361:BALR
1345:BXLE
1343:and
1188:Bit
1099:E=1
1088:Key
783:Key
243:Type
237:CISC
223:1983
216:1983
205:Bits
79:3090
75:308X
71:303X
1705:IBM
1681:IBM
1657:IBM
1605:IBM
1579:doi
1549:IBM
1507:BAL
1499:BAL
1461:.
1438:I/O
1416:BSM
1393:BSM
1385:BSM
1369:BAS
1365:BAS
1357:BAL
1341:BXH
1248:IA
1232:32
1220:23
1212:22
1204:21
1196:20
1176:PM
1165:CC
1147:16
1136:15
1125:14
1114:13
1096:12
1077:EX
1066:IO
1014:63
953:33
950:32
924:31
909:24
906:23
899:20
896:19
893:18
890:17
887:16
884:15
881:14
878:13
875:12
872:11
804:CC
722:63
659:32
636:31
530:31
433:31
286:Big
199:IBM
1721::
1655:.
1651:.
1633:.
1616:^
1607:.
1603:.
1599:.
1575:27
1573:.
1557:^
1525:^
1323:LA
1235:A
1150:S
1139:P
1128:W
1117:M
1074:7
1063:6
1055:T
1052:5
1044:R
1041:1
938:A
865:8
862:7
859:6
856:5
853:4
848:2
845:1
842:0
833:0
830:0
827:0
824:0
821:0
818:0
815:0
812:0
801:0
798:S
795:P
792:W
789:M
786:1
780:X
775:O
770:T
767:0
764:0
761:0
758:R
755:0
589:8
586:7
573:1
570:0
555:S
467:0
370:0
323:16
77:,
73:,
1659:.
1585:.
1581::
1468:)
1464:(
1107:C
1103:E
778:E
773:I
741:C
737:E
225:)
178:e
171:t
164:v
81:)
69:(
20:)
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