466:
269:
Early versions of the Amiga 2000B, and the most common "trapdoor memory expanded" configuration of the Amiga 500, contain 512 KiB pseudo-fast RAM ("slow RAM") controlled by Agnus with the same limitations as Chip RAM, yet unusable as such due to register limitations. Numerous budget trapdoor
236:
The maximum amount of Chip RAM in any model is 2 MiB. The Amiga 4000 motherboard includes a non-functional jumper that anticipated later chips and is labeled for 8 MiB of Chip RAM—regardless of its position, the system only recognizes 2 MiB due to the limitations of the Alice
64:
processor used in early Amiga systems usually only accesses memory on every second memory cycle, Agnus operates a system where the "odd" clock cycle is allocated to time-critical custom chip access and the "even" cycle is allocated to the CPU: thus, for average DMA demand, the CPU is not typically
229:). All models except the A1000 are upgradable to 2 MiB of Chip RAM. The A500 and the early A2000B can accommodate 1 MiB by installing a later revision Agnus chip (8732A) with minimal hardware modifications; late-production machines usually already contained that chip, so that only
224:
The maximum amount of Chip RAM is dependent on the Agnus/Alice version. The original Agnus chip fitted to the A1000 and early A2000 systems is a 48-pin DIP package able to address 512 KiB of Chip RAM. Subsequent versions of the Agnus are in an 84-pin PLCC package (either socketed or
249:
Amiga systems can also be expanded with Fast RAM, which is only accessible to the CPU. This improves execution speed, as CPU cycles are never blocked even when the custom chipset is simultaneously accessing Chip RAM. Adding Fast RAM to systems with 32-bit CPUs roughly doubles the
220:
is increased fourfold compared to the earlier 16-bit design. However, 32-bit access is limited to CPU and graphics DMA and cannot be used for other devices. The ECS-based A3000 also has 32-bit Chip RAM, but access is only 32-bit for CPU operations; the chipset remained 16-bit.
59:
models) chip. Both the CPU and other members of the chipset have to arbitrate for access to shared RAM via Agnus. This allows the custom chips to perform video, audio, or other DMA operations independently of the CPU. As the
73:
operations, can use any spare cycles, effectively blocking cycles from the CPU. In such situations CPU cycles are only blocked while accessing shared RAM, but never when accessing Fast (CPU-only) RAM (when present) or ROM.
215:
systems. The later AGA systems use a 32-bit data bus controlled by the Alice coprocessor (replacing Agnus) and 32-bit RAM. The memory clock runs at double the rate on AGA systems. As a result, chipset RAM
265:
expansion RAM, 32-bit motherboard RAM, and 32-bit CPU card RAM simultaneously (in increasing speed order). Automatically configured RAM is prioritized by the system, so the fastest memory is used first.
65:
blocked from memory access and may run without interruption. However, certain chipset DMA, such as high-resolution graphics with a larger color palette,
439:
499:
371:
343:
745:
56:
750:
387:
257:
Confusingly, a system may have several different kinds and speeds of Fast RAM. For example, an Amiga 3000 may contain 16-bit
492:
366:. Amiga Technical Reference Series (Third ed.). Reading, Massachusetts: Addison-Wesley Publishing Company, Inc.
316:
AGA Chip RAM access is 32-bit for CPU and graphics DMA only; audio, floppy, Copper, and blitter DMA remain 16-bit
524:
338:. Amiga Technical Reference Series. Reading, Massachusetts: Addison-Wesley Publishing Company, Inc. p. 180.
233:
modifications were necessary. Likewise, 2 MB can be installed by fitting an 8372B Agnus and extra memory.
226:
413:
740:
485:
251:
212:
32:
24:
755:
66:
36:
270:
expansions for the 500 extended this "controllerless" concept to up to 1.8 MB slow RAM (requiring a
254:, as the more advanced 68020, '030, and '040 CPUs can utilize more memory cycles than the earlier 68000.
885:
808:
793:
839:
803:
776:
760:
735:
514:
52:
48:
20:
813:
271:
230:
844:
730:
367:
339:
208:
391:
217:
82:
Most stock Amiga systems were equipped with Chip RAM only and shipped with between 256
880:
834:
906:
875:
628:
602:
542:
238:
146:
900:
870:
865:
860:
781:
693:
83:
798:
786:
709:
582:
471:
241:
can emulate an Amiga system with the design limit of up to 8 MiB of Chip RAM.
714:
592:
577:
597:
587:
572:
567:
562:
557:
552:
532:
461:
190:
186:
182:
166:
126:
106:
39:(hence the name). It was also, rather misleadingly, known as "graphics RAM".
547:
537:
262:
150:
122:
477:
688:
683:
678:
623:
618:
258:
668:
647:
70:
652:
417:
307:
A3000 Chip RAM is 32-bit for CPU access, 16-bit for chipset access
673:
508:
61:
28:
130:
481:
289:
Later A500/A2000 systems were equipped with 1 MiB
357:
355:
853:
822:
769:
723:
702:
661:
640:
611:
523:
493:
8:
298:Up to 2 MiB with hardware modification
19:is a commonly used term for the integrated
500:
486:
478:
31:computers. Chip RAM is shared between the
751:Amiga Advanced Architecture chipset (AAA)
88:
51:(DMA) controller is integrated into the
326:
237:chip. However, the software emulator
207:The shared RAM data bus is 16-bit on
7:
746:Advanced Graphics Architecture (AGA)
414:"Features of the UAE Amiga Emulator"
440:"List of A500 Trapdoor Expansions"
47:Under the Amiga architecture, the
14:
464:
336:Amiga User Interface Style Guide
311:
302:
293:
284:
138:512 KiB – 1 MiB
135:512 KiB – 1 MiB
35:(CPU) and the Amiga's dedicated
364:Amiga Hardware Reference Manual
362:Commodore-Amiga, Inc. (1991).
334:Commodore-Amiga, Inc. (1991).
1:
388:"A4000 Motherboard Jumpers"
923:
274:adapter for addressing).
814:other Amiga custom chips
731:Original Chip Set (OCS)
33:central processing unit
741:Enhanced Chipset (ECS)
281:
261:expansion RAM, 32-bit
886:Amiga video connector
756:Commodore AA+ Chipset
662:Unofficial PPC models
641:Unofficial 68k models
761:Amiga Hombre chipset
49:direct memory access
43:Direct memory access
394:on 23 November 2019
854:3rd Party Hardware
770:Amiga custom chips
894:
893:
373:978-0-201-56776-2
345:978-0-201-57757-0
252:instruction speed
205:
204:
98:Maximum Chip RAM
78:Chip RAM by model
914:
840:Extra Half-Brite
703:Amiga prototypes
518:
502:
495:
488:
479:
474:
469:
468:
467:
451:
450:
448:
446:
436:
430:
429:
427:
425:
416:. Archived from
410:
404:
403:
401:
399:
390:. Archived from
384:
378:
377:
359:
350:
349:
331:
315:
306:
297:
288:
89:
86:and 2 MiB.
922:
921:
917:
916:
915:
913:
912:
911:
897:
896:
895:
890:
881:Amiga Zorro III
849:
835:Hold-And-Modify
818:
765:
719:
698:
657:
636:
612:AmigaOne models
607:
519:
512:
506:
470:
465:
463:
460:
455:
454:
444:
442:
438:
437:
433:
423:
421:
412:
411:
407:
397:
395:
386:
385:
381:
374:
361:
360:
353:
346:
333:
332:
328:
323:
310:
301:
292:
283:
280:
247:
227:surface-mounted
95:Stock Chip RAM
80:
45:
12:
11:
5:
920:
918:
910:
909:
899:
898:
892:
891:
889:
888:
883:
878:
876:Amiga Zorro II
873:
868:
863:
857:
855:
851:
850:
848:
847:
842:
837:
832:
826:
824:
820:
819:
817:
816:
811:
806:
801:
796:
791:
790:
789:
784:
773:
771:
767:
766:
764:
763:
758:
753:
748:
743:
738:
736:Ranger Chipset
733:
727:
725:
724:Amiga chipsets
721:
720:
718:
717:
712:
706:
704:
700:
699:
697:
696:
691:
686:
681:
676:
671:
665:
663:
659:
658:
656:
655:
650:
644:
642:
638:
637:
635:
634:
633:AmigaOne X5000
631:
629:AmigaOne X1000
626:
621:
615:
613:
609:
608:
606:
605:
600:
595:
590:
585:
580:
575:
570:
565:
560:
555:
550:
545:
540:
535:
529:
527:
521:
520:
507:
505:
504:
497:
490:
482:
476:
475:
459:
456:
453:
452:
431:
405:
379:
372:
351:
344:
325:
324:
322:
319:
318:
317:
308:
299:
290:
279:
276:
246:
243:
203:
202:
199:
196:
193:
179:
178:
175:
172:
169:
163:
162:
159:
156:
153:
147:Amiga 500 Plus
143:
142:
139:
136:
133:
119:
118:
115:
112:
109:
103:
102:
99:
96:
93:
79:
76:
44:
41:
13:
10:
9:
6:
4:
3:
2:
919:
908:
905:
904:
902:
887:
884:
882:
879:
877:
874:
872:
871:Amiga Sidecar
869:
867:
866:Action Replay
864:
862:
861:Flicker fixer
859:
858:
856:
852:
846:
843:
841:
838:
836:
833:
831:
828:
827:
825:
821:
815:
812:
810:
807:
805:
802:
800:
797:
795:
792:
788:
785:
783:
780:
779:
778:
775:
774:
772:
768:
762:
759:
757:
754:
752:
749:
747:
744:
742:
739:
737:
734:
732:
729:
728:
726:
722:
716:
713:
711:
708:
707:
705:
701:
695:
694:Sam460ex Lite
692:
690:
687:
685:
684:Sam440ep-flex
682:
680:
677:
675:
672:
670:
667:
666:
664:
660:
654:
651:
649:
646:
645:
643:
639:
632:
630:
627:
625:
622:
620:
617:
616:
614:
610:
604:
601:
599:
596:
594:
591:
589:
586:
584:
581:
579:
576:
574:
571:
569:
566:
564:
561:
559:
556:
554:
551:
549:
546:
544:
541:
539:
536:
534:
531:
530:
528:
526:
522:
516:
510:
503:
498:
496:
491:
489:
484:
483:
480:
473:
462:
457:
441:
435:
432:
420:on 2017-01-05
419:
415:
409:
406:
393:
389:
383:
380:
375:
369:
365:
358:
356:
352:
347:
341:
337:
330:
327:
320:
314:
313:
309:
305:
304:
300:
296:
295:
291:
287:
286:
282:
277:
275:
273:
267:
264:
260:
255:
253:
244:
242:
240:
234:
232:
228:
222:
219:
214:
210:
200:
197:
194:
192:
188:
184:
181:
180:
176:
173:
170:
168:
165:
164:
160:
157:
154:
152:
148:
145:
144:
140:
137:
134:
132:
128:
124:
121:
120:
116:
114:512 KiB
113:
111:256 KiB
110:
108:
105:
104:
100:
97:
94:
91:
90:
87:
85:
77:
75:
72:
68:
63:
58:
54:
50:
42:
40:
38:
34:
30:
26:
22:
18:
829:
799:Denise (OCS)
624:AmigaOne 500
525:Amiga models
472:Amiga portal
443:. Retrieved
434:
422:. Retrieved
418:the original
408:
396:. Retrieved
392:the original
382:
363:
335:
329:
312:
303:
294:
285:
268:
256:
248:
235:
223:
206:
81:
46:
16:
15:
794:Alice (AGA)
715:Power A5000
398:2 September
198:2 MiB
195:2 MiB
174:2 MiB
171:1 MiB
158:2 MiB
155:1 MiB
27:'s line of
804:Lisa (AGA)
445:3 November
321:References
191:Amiga CD32
187:Amiga 4000
183:Amiga 1200
167:Amiga 3000
127:Amiga 2000
107:Amiga 1000
55:(Alice on
845:Kickstart
511:hardware
424:4 January
263:Zorro III
218:bandwidth
151:Amiga 600
123:Amiga 500
25:Commodore
901:Category
830:Chip RAM
823:Hardware
689:Sam460ex
679:Sam440ep
619:AmigaOne
543:500 Plus
458:See also
259:Zorro II
245:Fast RAM
23:used in
17:Chip RAM
782:Blitter
669:Pegasos
648:Minimig
515:history
201:32-bit
177:32-bit
161:16-bit
141:16-bit
117:16-bit
71:blitter
37:chipset
787:Copper
710:Walker
653:Natami
583:3000UX
370:
342:
231:jumper
101:Width
92:Model
67:Copper
907:Amiga
809:Paula
777:Agnus
674:Efika
593:4000T
578:3000T
509:Amiga
278:Notes
69:, or
62:68000
53:Agnus
29:Amiga
603:CDTV
598:CD32
588:4000
573:3000
568:2500
563:2000
558:1500
553:1200
533:1000
447:2018
426:2017
400:2011
368:ISBN
340:ISBN
272:Gary
211:and
131:CDTV
548:600
538:500
239:UAE
213:ECS
209:OCS
84:kiB
57:AGA
21:RAM
903::
354:^
189:,
185:,
149:,
129:,
125:,
517:)
513:(
501:e
494:t
487:v
449:.
428:.
402:.
376:.
348:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.