451:". This presented a potential problem with the new drive; if a user flipped the disk and formatted using the default double-sided format, any data on the other side would be erased. To prevent this, the system only allowed formatting if the disk's timing hole was in the correct "up" position, otherwise it would only format in the older single-sided formats. For those that needed to make flippys for use with other drives, the XF551 Enhancer appeared, a modification that allowed the drive to ignore the timing hole and write to either side of the disk.
462:. They can be distinguished as the Mitsumi version has a rectangular LED on the front while the Chinon version is round. The Chinon versions also used the timing hole for both formatting and reading, and thus could not work with flippy disks at all. This limitation could be removed with the Enhancer. Because the drive mechanism was connected to the board using a standard connector, it was possible to replace it with a 3.5-inch mechanism, and this became quite popular.
20:
383:
141:
251:
350:
Prior to the
Nintendo lawsuit, Atari claimed the only holdup on the new drive was that the documentation for the new DOS was not ready. When the lawsuit was launched, Atari put the drive on the market immediately in June 1987, shipping it with the existing Atari DOS 2.5. This was a success, as it did
286:
As part of the XEGS launch, Atari boasted about its large library of software as well as its ability to be used as a true computer with the supplied keyboard and optional peripherals including a floppy drive. By this point, stocks of the 1050 had already run out. This led to about six months where no
414:
that sends commands and data over the same in and out pins. This requires the devices on the SIO to be "smart", listening for commands being sent to their device number, decoding the instructions, and responding in kind. In previous Atari drives, this had been accomplished with the 6507, a cut-down
362:
The drive was otherwise very well received. It was "eerily silent during operation", so much so that reviews noted it was impossible to tell if it was being used without looking at the access LED. The only real complaints were the rear position of the power button, which made it difficult to access
322:
running at 500 kHz. For historical reasons, these drives used a 19.2 kbps speed to transfer data, although this was not a limitation of the bus itself. Third party drives normally used higher speeds, when run with suitable third-party DOSes, with some operating as high as the 52 kbps
176:
at a higher price point, and its lineup could not be produced profitably at the rapidly falling market prices. Atari eventually introduced lower-cost models, the 600XL and 800XL, but these were repeatedly delayed and did not reach market until late in 1983, too late to have an impact. Combined with
127:
standard that provided up to 180 kB of storage. For reasons unknown, Atari's DOS for the machine did not support the double-density format, instead it used a new format known alternately as "enhanced density" or "dual density" with 130 kB. Several 3rd party DOS products emerged that fully
438:
that included ROM and RAM on the same chip and thus allowed a great simplification of the controller. The 8040 versions did not have enough ROM for the entire driver, so later models moved to the 8050 with 4 kB for a further simplification. These chips, originally introduced in 1976, were now
241:
When the
Tramiels took over the company they found huge stocks of unsold 1050s, and repeatedly delayed the XF521 while selling these off. By the time the stocks of these drives finally dwindled in 1986, the ST was selling strongly and the company had lost interest in the 8-bit line. Any mention of
51:
of the XE models. It was the first drive from the company with official support for double-density and double-sided floppy disks—360 kB of storage per disk—and was also the final floppy disk drive Atari produced for the 8-bit computers. The XF551 allows faster transfer speed when used in
354:
However, DOS 2.5 lacked support for the new modes, which essentially made it a direct replacement for the 1050 rather than the major upgrade it was intended to be. DOS XE did not ship until 1988/89, by which time the same modes were already supported by a variety of 3rd party solutions like
302:
At some point during this period, Atari decided to completely redesign the drive. The computer market was already well into the conversion from 5.25 to 3.5-inch disks, and 5.25 double-density double-sided drives were now commonplace and inexpensive. Moreover, after the introduction of the
472:
One design feature of DOS XE was that it always wrote files to side one of the floppy until it ran out of room. This meant the disks could be inserted in older drives also being run with DOS XE, or compatible double-density 3rd party DOSes, and at least read the files on that side.
402:
When operating in legacy modes to read or write to disks from the 810 or 1050, the system transferred data at the original standard speed of 19,040 bps. This speed was much lower than the SIO was capable of, and had been selected simply because that was the limit of the
390:
The XF551 was slightly smaller than the 1050 it replaced, but overall similar. It connected to the computer or XEGS using the SIO port, with two ports on the back, in and out, to allow it to be daisy chained to other peripherals. The back also had the jack for the
366:
By the late 1980s, sales of the XE series were primarily to low-cost markets like eastern Europe and South
America. These markets were so cost-sensitive that even the low price of the XF551 was too much for most users, and the most common storage mechanism was the
363:
in some computer desks, and that it was very "fussy" about the diskettes, rejecting as many as 20% of low-cost floppies. In the end, it was "heartily recommend"ed, and "the best thing that's happened to Atari's 8-bit computer line since the birth of the 130XE".
70:, boasting it could be expanded to a complete computer with the addition of a keyboard and disk drive. Nintendo sued, noting that Atari had no disk drives to sell, forcing Atari to rush the drive to market in June 1987 even though the software was not ready.
234:. The 8048 included internal RAM and ROM and thus greatly simplified the overall design of the interface. The Tramiels took the CR and repackaged it to match the silver-grey styling of the XE and ST line. While introducing the XE's at the January 1985
73:
The XF551 is generally considered the best of Atari's drive offerings; not only does it store three times as much data as the 1050, it is twice as fast and almost silent in operation. Its release was marred by packaging it with an old version of
111:
format of 180 kB. Small numbers of the 815 began shipping in June 1980, but mass production never started. Nevertheless, this brief introduction set the standard for double-density drives that other companies would later support.
333:
2.5, introduced for the 1050 in 1983, did not support either capability. This had led to a thriving market for 3rd party DOSes which had long supported double-density modes and the higher transfer speeds. Among these was
278:
which were put back on the market, but neither had been in production for some time and were built on pre-XE systems with no capability to produce more. This led to the decision to introduce a new console, the
443:
floppy disk controller, a late-model version of WD's drive controllers that implemented almost all of the required circuitry in a single 28-pin chip and thereby lowered the total cost of implementation.
342:(OSS), authors of the original Atari DOS. Atari contracted OSS to produce a new version, initially known as ADOS, which added double-sided support to its existing double-density and high-speed features.
465:
In contrast to the 810 and 1050, which ran at the non-standard speed of 288 RPM, the XF551 ran at the industry standard 300 RPM. This caused problems for a small number of programs whose
847:
386:
The rear panel of the XF551 held (from left to right) a power switch, the jack for the external power supply, the two SIO ports and the small DIP switches for selecting the drive number.
59:
were sold off. By the time these ran out late in 1986, interest in the 8-bit line had waned and a new model was not put into production. At the same time, the success of the
211:, to market as soon as possible. During this period many advanced projects within the company were cancelled. This included Atari's own 32-bit efforts and several advanced
568:
447:
Previous to the XF551, users would generally use both sides of a floppy disk by formatting one side, flipping the disk over, and formatting the second, the so-called "
78:
which does not support the new features. This was addressed with DOS XE a year later. Support was dropped, along with the entire 8-bit computer line, in 1992.
207:
Attempting to bring the company back to some semblance of profitability, the new management laid off whole divisions while working to bring their new
215:. Warehouses filled with stocks of the 8-bit line were sold off at fire-sale prices pending the introduction of cost-reduced models, the XE series.
196:, and left the company. After spending some time looking for ways to re-enter the field, in July he arranged a deal to buy Atari from its owners,
223:
Atari had already been working on several upgrades to the 1050 series, including the 1050CR, for cost-reduced. This replaced the original custom
856:, ...huge roomful of 1 MHz but not 1.1 MHz devices. So that's what they put in the peripherals, was 6507 that they had surplus lying around....
867:
407:
available to the engineers designing the original 810s. The XF551, when operating in double-density mode, doubled this to 38,908 bps.
144:
The 130XE and similar 65XE were cost-reduced versions of the 8-bit line that could be produced at price points similar to the
Commodore 64.
107:
format that stored about 90 kB of data, while the 815 packaged two drives in a single case, both supporting a double-density
55:
Although an XE-styled drive was shown several times during 1985 and 1986, production waited while leftover inventories of the
327:. For the new drive, Atari decided to double the rate to 38 kbps, although only when used with double-density disks.
1042:
287:
official Atari drives were available for the line, and it appeared the company was in no hurry to introduce the XF521.
973:
681:
119:
in 1982, the company introduced a new line of peripherals matching the styling of the new machine. This included the
254:
The XEGS was a repackaged 65XE, supplied with a separate keyboard that allowed it to be used as a complete computer.
439:
available for pennies and ran at a relatively fast 8.33 MHz. The controller was paired with the then-standard
590:
427:
failed to run at this speed reliably and were passed off to be used as SIO controllers running at lower speeds.
238:, the company previewed the design as the XF521. It was rumored it would also support true double-density mode.
1062:
1010:
621:
555:
TI started a price war and drove
Commodore out of the market. Tramiel was not about to let that happen again.
359:. Nevertheless, shipping DOS 2.5 with the drives for over a year led to significant confusion in the market.
263:
184:
The success of the C64 did not save
Commodore from problems of its own. In January 1984, Commodore president
124:
60:
984:
430:
For the new drive, which operated at higher speeds and had more features, the 6507 was replaced by the
339:
997:
294:, noting that Atari claimed the system supported a floppy but did not actually have drives for sale.
235:
132:
that offered double-density from the start, along with additional features and improved performance.
941:
915:
178:
1057:
266:
to North
America. By late 1986 it was a runaway success, prompting the Tramiels to reexamine the
149:
489:
It was speculated at the time that the dual heads on the drive pressed too tightly on the disk.
440:
671:
538:
1019:
640:
314:
Earlier Atari drives used a customized controller that communicated with the host computer's
304:
189:
92:
44:
1037:
928:
545:. Vol. 12, no. 4. Austin, Texas: Emmis Communications. pp. 136–139, 216–226.
8:
416:
224:
267:
212:
67:
969:
677:
546:
459:
291:
283:, which was essentially a repackaged Atari 65XE and would run existing 8-bit games.
455:
963:
466:
435:
231:
201:
48:
458:
mechanism, although a small number of later models replaced this with one from
404:
1051:
550:
371:
157:
954:
829:
431:
392:
324:
308:
193:
185:
173:
165:
116:
108:
448:
311:
had proliferated. This allowed internal mechanisms to be easily swapped.
197:
104:
96:
40:
36:
19:
382:
420:
411:
396:
280:
275:
271:
228:
120:
64:
56:
423:
console. The console ran at 1.1 MHz, but some 6507s supplied by
374:
system. The entire 8-bit series was eventually discontinued in 1992.
368:
356:
330:
315:
153:
100:
75:
23:
The XF551 matches the grey styling of the XE series machines and the
424:
319:
259:
208:
169:
129:
24:
673:
The Game
Console 2.0: A Photographic History from Atari to Xbox
335:
161:
140:
250:
738:
181:, the company was soon losing over a million dollars a day.
123:, a new disk drive that was built around the double-density
998:"Atari's New Super Disk Drive: First look inside the XF551"
736:
734:
732:
730:
728:
726:
724:
722:
720:
718:
103:
and the 815. The 810 used the then-standard single-density
508:
506:
787:
785:
783:
753:
751:
128:
supported double-density, as well as new drives like the
965:
Breakout: How Atari 8-Bit
Computers Defined a Generation
715:
705:
703:
701:
699:
697:
695:
693:
518:
503:
891:
879:
809:
797:
780:
748:
577:...which reported a $ 180 million loss this quarter...
770:
768:
766:
690:
651:
601:
63:(NES) prompted Atari to repackage their 65XE as the
399:that allowed the drive to be numbered 1 through 4.
763:
641:"First Look Inside the New Atari Super Computers"
270:market. At the time, Atari had warehouses of the
1049:
1011:"ANTIC Interview 177 - Steve Smith, ANTIC chip"
160:market by repeatedly lowering the price of its
866:"WD1772-02 Floppy Disk Formatter/Controller".
1038:Atari DOS 2.5 XF551 Disk Drive Owner's Manual
1017:
524:
52:double-density mode, doubling performance.
569:"Atari Sends Warner Loss to $ 122 Million"
47:. Introduced in 1987, it matches the gray
926:
885:
869:1986 Storage Management Products Handbook
821:
638:
227:-based interface card with one using the
95:began shipping in 1979, Atari showed two
995:
939:
913:
897:
803:
791:
757:
709:
530:
381:
249:
139:
18:
1018:Dziefielewski, Lawrence (August 1984).
961:
952:
815:
742:
657:
607:
512:
469:relied on accurately timing the drive.
1050:
1008:
875:. Western Digital. 1986. p. 1.27.
853:
588:
566:
536:
982:
774:
619:
351:result in the lawsuit being dropped.
200:, for no cash and several million in
168:(C64) lines in order to undercut the
953:Current, Michael (12 October 2021).
827:
669:
188:got into some sort of argument with
172:. Atari had recently introduced the
914:Ratcliff, Matthew (February 1989).
567:Shrage, Michael (15 October 1983).
307:, drives using the standard 34-bit
135:
13:
1031:
940:van Dijk, Jerry (September 1989).
14:
1074:
1009:Savetz, Kevin (9 February 2016).
86:
245:
907:
859:
676:. No Starch Press. p. 10.
663:
626:Saint Paul Computer Enthusiasts
591:"Warner Sells Atari To Tramiel"
483:
454:Most of the drives sold used a
345:
115:During the introduction of the
948:. No. 76. pp. 54–55.
927:Ratcliff, Matthew (May 1989).
922:. No. 69. pp. 9, 40.
632:
620:Floyd, Bob (11 January 1985).
613:
582:
560:
377:
1:
639:Friedland, Nat (April 1985).
589:Sanger, David (3 July 1984).
537:Nocera, Joseph (April 1984).
496:
264:Nintendo Entertainment System
61:Nintendo Entertainment System
996:Tietjens, Rich (June 1988).
7:
1043:Atari DOS XE Owner's Manual
983:Blake, Peter (March 1989).
419:that was being used in the
297:
10:
1079:
395:, the power switch, and a
340:Optimized Systems Software
81:
236:Consumer Electronics Show
1026:. pp. 36–39, 80–81.
916:"Atari XF551 Disk Drive"
830:"Atari XEGS Information"
476:
338:, introduced in 1983 by
290:Nintendo sued Atari for
218:
179:video game crash of 1983
962:Lendino, Jamie (2017).
242:the XF521 disappeared.
150:Commodore International
441:Western Digital FD1772
387:
255:
145:
28:
1063:Atari 8-bit computers
539:"Death of a Computer"
385:
253:
198:Warner Communications
190:chairman of the board
143:
93:Atari 8-bit computers
45:Atari 8-bit computers
22:
323:"Warp Speed" of the
1020:"Disk Drive Survey"
828:Ratcliff, Matthew.
670:Amos, Evan (2021).
573:The Washington Post
177:the effects of the
99:drive systems, the
622:"XF521 Disk Drive"
595:The New York Times
525:Dziefielewski 1984
388:
256:
146:
68:video game console
39:drive produced by
29:
1004:. pp. 46–47.
955:"atari-8-bit/faq"
460:Chinon Industries
292:false advertising
258:In October 1985,
16:Floppy disk drive
1070:
1027:
1014:
1005:
992:
979:
958:
949:
942:"XF551 Commands"
936:
935:. pp. 7, 8.
929:"XF551 Enhancer"
923:
901:
895:
889:
883:
877:
876:
874:
863:
857:
851:
845:
844:
842:
840:
825:
819:
813:
807:
801:
795:
789:
778:
772:
761:
755:
746:
745:, p. 3.2.3.
740:
713:
707:
688:
687:
667:
661:
655:
649:
648:
636:
630:
629:
617:
611:
605:
599:
598:
586:
580:
579:
564:
558:
557:
534:
528:
522:
516:
515:, p. 3.2.4.
510:
490:
487:
456:Mitsumi Electric
436:microcontrollers
202:promissory notes
136:Turmoil at Atari
35:is a 5 1/4 inch
1078:
1077:
1073:
1072:
1071:
1069:
1068:
1067:
1048:
1047:
1034:
1032:Further reading
991:. pp. 3–4.
976:
910:
905:
904:
896:
892:
884:
880:
872:
865:
864:
860:
852:
848:
838:
836:
826:
822:
814:
810:
802:
798:
790:
781:
773:
764:
756:
749:
741:
716:
708:
691:
684:
668:
664:
656:
652:
637:
633:
618:
614:
606:
602:
587:
583:
565:
561:
535:
531:
523:
519:
511:
504:
499:
494:
493:
488:
484:
479:
467:copy protection
415:version of the
380:
348:
300:
262:introduced the
248:
232:microcontroller
221:
138:
89:
84:
49:design language
17:
12:
11:
5:
1076:
1066:
1065:
1060:
1058:Atari hardware
1046:
1045:
1040:
1033:
1030:
1029:
1028:
1015:
1006:
993:
980:
974:
968:. Ziff Davis.
959:
950:
937:
924:
909:
906:
903:
902:
890:
886:Ratcliffa 1989
878:
858:
846:
820:
818:, p. 110.
808:
796:
779:
762:
747:
714:
689:
682:
662:
660:, p. 112.
650:
631:
612:
600:
581:
559:
529:
517:
501:
500:
498:
495:
492:
491:
481:
480:
478:
475:
405:logic analyzer
379:
376:
347:
344:
299:
296:
247:
244:
220:
217:
152:sparked off a
137:
134:
88:
87:Earlier drives
85:
83:
80:
15:
9:
6:
4:
3:
2:
1075:
1064:
1061:
1059:
1056:
1055:
1053:
1044:
1041:
1039:
1036:
1035:
1025:
1021:
1016:
1012:
1007:
1003:
999:
994:
990:
986:
985:"XL/XE XF551"
981:
977:
975:9780692851272
971:
967:
966:
960:
956:
951:
947:
943:
938:
934:
930:
925:
921:
917:
912:
911:
900:, p. 47.
899:
898:Tietjens 1988
894:
887:
882:
871:
870:
862:
855:
850:
835:
831:
824:
817:
812:
806:, p. 54.
805:
804:van Dijk 1989
800:
794:, p. 40.
793:
792:Ratcliff 1989
788:
786:
784:
776:
771:
769:
767:
760:, p. 46.
759:
758:Tietjens 1988
754:
752:
744:
739:
737:
735:
733:
731:
729:
727:
725:
723:
721:
719:
711:
710:Ratcliff 1989
706:
704:
702:
700:
698:
696:
694:
685:
683:9781718500617
679:
675:
674:
666:
659:
654:
647:. p. 19.
646:
642:
635:
627:
623:
616:
610:, p. 99.
609:
604:
597:. p. D1.
596:
592:
585:
578:
574:
570:
563:
556:
552:
548:
544:
543:Texas Monthly
540:
533:
526:
521:
514:
509:
507:
502:
486:
482:
474:
470:
468:
463:
461:
457:
452:
450:
445:
442:
437:
433:
428:
426:
422:
418:
413:
408:
406:
400:
398:
394:
384:
375:
373:
372:cassette tape
370:
364:
360:
358:
352:
343:
341:
337:
332:
328:
326:
321:
317:
312:
310:
306:
295:
293:
288:
284:
282:
277:
273:
269:
268:games console
265:
261:
252:
246:Nintendo sues
243:
239:
237:
233:
230:
226:
216:
214:
213:game consoles
210:
205:
203:
199:
195:
191:
187:
182:
180:
175:
171:
167:
163:
159:
158:home computer
155:
151:
142:
133:
131:
126:
122:
118:
113:
110:
106:
102:
98:
94:
79:
77:
71:
69:
66:
62:
58:
53:
50:
46:
42:
38:
34:
26:
21:
1023:
1013:(Interview).
1001:
988:
964:
945:
932:
919:
908:Bibliography
893:
888:, p. 7.
881:
868:
861:
849:
839:February 28,
837:. Retrieved
833:
823:
816:Lendino 2017
811:
799:
777:, p. 3.
743:Current 2021
712:, p. 9.
672:
665:
658:Lendino 2017
653:
644:
634:
625:
615:
608:Lendino 2017
603:
594:
584:
576:
572:
562:
554:
542:
532:
520:
513:Current 2021
485:
471:
464:
453:
446:
429:
409:
401:
393:power supply
389:
365:
361:
353:
349:
346:Introduction
329:
318:bus using a
313:
309:ribbon cable
301:
289:
285:
257:
240:
222:
206:
194:Irving Gould
186:Jack Tramiel
183:
174:Atari 1200XL
166:Commodore 64
147:
125:MFM encoding
117:Atari 1200XL
114:
109:MFM encoding
90:
72:
54:
32:
30:
854:Savetz 2016
449:flippy disk
378:Description
105:FM encoding
97:floppy disk
41:Atari, Inc.
37:floppy disk
1052:Categories
775:Blake 1989
497:References
432:Intel 8040
412:serial bus
397:DIP switch
281:Atari XEGS
276:Atari 7800
272:Atari 5200
229:Intel 8048
121:Atari 1050
65:Atari XEGS
57:Atari 1050
551:0148-7736
421:Atari VCS
410:SIO is a
357:SpartaDOS
331:Atari DOS
325:Happy 810
316:Atari SIO
154:price war
148:In 1983,
91:When the
76:Atari DOS
425:Synertek
417:MOS 6502
320:MOS 6507
298:Redesign
260:Nintendo
225:MOS 6507
209:Atari ST
170:TI-99/4A
130:Indus GT
43:for the
25:Atari ST
834:AtariHQ
156:in the
82:History
989:Status
972:
946:ANALOG
920:ANALOG
680:
549:
336:DOS XL
305:IBM PC
162:VIC-20
1024:ANTIC
1002:Antic
933:ANTIC
873:(PDF)
645:ANTIC
477:Notes
219:XF521
33:XF551
970:ISBN
841:2021
678:ISBN
547:ISSN
369:XC12
274:and
164:and
31:The
101:810
1054::
1022:.
1000:.
987:.
944:.
931:.
918:.
832:.
782:^
765:^
750:^
717:^
692:^
643:.
624:.
593:.
575:.
571:.
553:.
541:.
505:^
434:,
204:.
192:,
978:.
957:.
843:.
686:.
628:.
527:.
27:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
