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══════════════════════════════════════════════════════════ COMPARISON BETWEEN DOS FORMAT, FDFORMAT 1.8 AND 2M/2MF 2.0 ══════════════════════════════════════════════════════════ Note: If you are a DISKCOPY or FORMAT programs programmer, read the note at the end of this file as soon as possible. 2M is not only the highest capacity formatter at this moment, but also 2M diskettes are the faster ones. This test will show it to you. Note that some absolute results may slightly vary from one computer to another, but the relation between formatter programs doesn't vary. If you decide to use 2M, you will realize that default formats (820/1476K and 984/1804/3608K) are also as reliable as DOS standard 360K/1.2M and 720K/1.44/2.88M). 1. - MAXIMUM STORAGE AFTER FORMAT. ────────────────────────────────── Physical limits are 1,025,000 for 5¼-DD (with 82 tracks) and 1,708,224 bytes in 5¼-HD. In 3½-DD (high density controller card at 300 Kbit/sec) the limit is 1,230,000 bytes; in 3½-HD, 2,050,000 bytes. ┌────────────────────┬────────────────────┐ │ Double Density │ High Density │ ┌──────────────────────┼────────────────────┼────────────────────┼──────┐ │ FORMAT (40/80t) │ 368,640 (360K) │ 1,228,800 (1,200K) │ │ │ FDFORMAT (82t) │ 839,680 (820K) │ 1,511,424 (1,476K) │ 5.25 │ │ 2MF /F (82t) │ 839,680 (820K) │ 1,511,424 (1,476K) │ │ │ 2MF /M (82t) │ 923,648 (902K) │ 1,595,392 (1,558K) │ (5¼) │ ├──────────────────────┼────────────────────┼────────────────────┼──────┤ │ FORMAT (40/80t) │ 737,280 (720K) │ 1,474,560 (1,440K) │ │ │ FDFORMAT (82t) │ 839,680 (820K) │ 1,763,328 (1,722K) │ 3.5 │ │ 2MF /F (82t) │ 1,007,616 (984K) │ 1,847,296 (1,804K) │ │ │ 2MF /M (82t) │ 1,091,584 (1,066K) │ 1,931,254 (1,886K) │ (3½) │ └──────────────────────┴────────────────────┴────────────────────┴──────┘ ┌────────────────────┐ │ Extra High Density │ ┌──────────────────────┼────────────────────┼──────┐ │ FORMAT (40/80t) │ 2,949,120 (2,880K) │ │ │ 2MF /F (82t) │ 3,694,592 (3,608K) │ 3.5 │ │ 2MF /M (82t) │ 3,862,528 (3,772K) │ (3½) │ └──────────────────────┴────────────────────┴──────┘ 2. - PERFORMANCE AT DOS LEVEL. ────────────────────────────── In order to compare the real performance of different diskette formats, here are the results of a simple test. To simplify, only 3.5-HD diskette results are shown. The TEST directory of hard disk contained two files of 256 Kb, 3 files of 128 Kb, 4 files of 64 Kb, 5 files of 32 Kb, 6 files of 16 Kb and 1 file of 15.5 Kb, totalling 1423.5 Kb on 21 files. Write test: COPY C:\TEST\*.* B: Read test: COPY /B B:\*.* NUL ┌────────────────┬─────────┬─────────┬─────────┬─────────┬─────────┬─────────┐ │ Disk Size │ 1.44 │ 1.44 │ 1.64 │ 1.72 │ 1.80 │ 1.88 │ ├────────────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┤ │ Formatter │ FORMAT │FDFORMAT │FDFORMAT │FDFORMAT │ 2MF │ 2MF │ ├────────────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┤ │ Write time │ 1:17.27 │ 1:06.72 │ 1:00.74 │ 1:27.05 │ 1:15.30 │ 1:23.93 │ ├────────────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┤ │ Read time │ 0:59.82 │ 0:48.50 │ 0:44.11 │ 1:05.69 │ 0:43.78 │ 0:54.16 │ ├────────────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┤ │ Free space left│ 0 │ 0 │ 203,776 │ 287,744 │ 370,688 │ 454,656 │ ├────────────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┤ │ Write (Kb/sec) │ 18.42 │ 21.34 │ 23.44 │ 16.35 │ 18.90 │ 16.96 │ ├────────────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┤ │ Read (Kb/sec) │ 23.80 │ 29.35 │ 32.27 │ 21.67 │ 32.51 │ 26.28 │ ├────────────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┤ │ Kb/sec average │ 21.11 │ 25.35 │ 27.86 │ 19.01 │ 25.71 │ 21.62 │ │ Relative Index │ 100.00 │ 120.09 │ 131.98 │ 90.05 │ 121.79 │ 102.42 │ └────────────────┴─────────┴─────────┴─────────┴─────────┴─────────┴─────────┘ Notes: - The test was executed on MS-DOS 6.2 with only 2M and FDREAD in memory. - /B switch is necessary to COPY binary files onto character device as NUL. - Reading from hard disk takes 5.5 sec (measured with the command COPY /B C:\TEST\*.* NUL), this time was subtracted from write test's time. - Diskette drive motor was on when COPY started. - FDFORMAT diskettes were formatted with /X:2 and /Y:3 switches. 3. - PERFORMANCE AT FULL-TRACK ACCESS LEVEL. ──────────────────────────────────────────── This results are obtained with the 2M-FDTR (Floppy Data Transfer Rate) utility, which reads/writes a complete diskette in whole-track blocks, always taking care on never using buffers across 64K DMA frontier (which will results in less performance). All statistics shown are in Kb/sec. The physical limits are: 36,62 Kb/sec at 300 Kbps (5¼-DD and 2M 3½-DD) and 61,03 Kb/sec at 500 Kbps (5¼-HD and 3½-HD). This results are only possible on AT computers. ┌────────────────┬────────────────┬────────────────┐ │ Double Density │ High Density │ Extra High D. │ ├────────────────┼────────────────┼────────────────┤ │ Read Write │ Read Write │ Read Write │ ┌───────────────┼────────────────┼────────────────┼────────────────┼──────┐ │ FORMAT │ 18.16 18.16 │ 30.13 30.13 │ │ │ │ FDFORMAT (*) │ 22.11 22.12 │ 39.73 39.73 │ │ 5.25 │ │ FDFORMAT (**) │ 25.00 25.00 │ 25.26 25.23 │ │ │ │ 2MF /F │ 25.04 25.00 │ 46.33 46.33 │ │ (5¼) │ │ 2MF /M │ 16.49 16.49 │ 28.50 28.47 │ │ │ ├───────────────┼────────────────┼────────────────┼────────────────┼──────┤ │ FORMAT │ 15.05 15.05 │ 30.14 30.14 │ ??.?? ??.?? │ │ │ FDFORMAT (*) │ 19.32 19.32 │ 39.58 39.53 │ -- -- │ 3.5 │ │ FDFORMAT (**) │ 21.78 21.75 │ 24.79 24.79 │ -- -- │ │ │ 2MF /F │ 25.72 25.76 │ 48.49 48.50 │ ??.?? ??.?? │ (3½) │ │ 2MF /M │ 16.25 16.25 │ 28.74 28.77 │ ??.?? ??.?? │ │ └───────────────┴────────────────┴────────────────┴────────────────┴──────┘ (*) DOS standard formats (360-720-1.2-1.44) and best /X and /Y. (**) Maximum capacity formats (820-1.48-1.72) and best /X and /Y. 4. - FORMAT TIME. ───────────────── All results are been obtained in a 386-25 computer. ┌────────────────┬────────────────┬────────────────┐ │ Double Density │ High Density │ Extra High D. │ ┌───────────────┼────────────────┼────────────────┼────────────────┼──────┐ │ FORMAT │ 0:37 │ 1:13 │ │ │ │ FDFORMAT (*) │ 0:42 │ 1:24 │ │ 5.25 │ │ FDFORMAT (**) │ 1:28 │ 1:52 │ │ │ │ 2MF /F │ 1:24 │ 1:30 │ │ (5¼) │ │ 2MF /M │ 2:33 │ 2:34 │ │ │ ├───────────────┼────────────────┼────────────────┼────────────────┼──────┤ │ FORMAT │ 1:24 │ 1:34 │ ?:?? │ │ │ FDFORMAT (*) │ 1:38 │ 1:42 │ -- │ 3.5 │ │ FDFORMAT (**) │ 1:46 │ 2:17 │ -- │ │ │ 2MF /F │ 1:37 │ 1:45 │ ?:?? │ (3½) │ │ 2MF /M │ 2:46 │ 3:19 │ ?:?? │ │ └───────────────┴────────────────┴────────────────┴────────────────┴──────┘ (*) DOS standard formats (360-720-1.2-1.44) and best /X and /Y. (**) Maximum capacity formats (820-1.48-1.72) and best /X and /Y. 5. - PROGRAMMERS NOTE. ────────────────────── The /X and /Y switches of Christoph H. Hochstätter FDFORMAT used in all the above tests are listed here, and are the best options in most cases in the AT systems (not in PC/XT): ┌─────────────────────┐ │ /X /Y │ ┌───────┼──────────┬──────────┤ │ 5¼-DD │ 1 │ 3 │ │ 5¼-HD │ 2 │ 3 │ │ 3½-DD │ 1 │ 2 │ │ 3½-HD │ 2 │ 3 │ └───────┴──────────┴──────────┘ Too many disk copy programs I have tested until now don't get the maximun speed possible. When a 1.44M diskette is formatted with a correct sector sliding (using /X:2 and /Y:3 FDFORMAT options for example) a whole diskette must be read or write in 36 seconds, at sector access level. If the read/write buffer cross a 64K DMA frontier, the access is divided in some phases and many tracks needs more than one disk revolution. Some of the copy programs also write the tracks in a temporary file on hard disk just when read it from diskette, instead of wait until all memory becomes full. So, these programs are all slow because each track requires more than one disk revolution to be accesed. Also while using the DOS standard (incorrect) sector sliding of /X:0 and /Y:0, a whole disk read or write time is never above 48 seconds in 1.44M media. The sector sliding consist in a different numbering order of sectors in the tracks. Example with /X:2 (in head changes) and /Y:3 (track changes): Cyl 0 Side 0: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Cyl 0 Side 1: 17 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Cyl 1 Side 0: 14 15 16 17 18 1 2 3 4 5 6 7 8 9 10 11 12 13 Cyl 1 Side 1: 12 13 14 15 16 17 18 1 2 3 4 5 6 7 8 9 10 11 When diskette drive changes the side or cylinder active, some time is spent ... and may be sufficient to can not read or write the next track when drive head begins the operation (needed wait to next revolution). The memory is also divided in 64K areas by the DMA controller. No disk operations are possible involving two of this areas. For example, in the direction 1FE3:0000 a sector can not be read or write, because the memory directions involved are from 1FE3:0000 to 1FE3:01FF (from absolute 1FE30 to absolute 2002F, in DMA pages 1 and 2). When DOS is loaded in computer, the BIOS INT 13h is fixed, maybe using an internal buffer... but disk performace get down, because disk operation is divided in some phases. Remember: use the correct sector sliding in your disk formats and never lets your program to cross any DMA frontier, if possible. If you think that is impossible to read or write 1.44M FDFORMAT /X:2 /Y:3 diskette in only 36 seconds ... or 1.80M 2M diskette in 37 seconds... execute 2M-FDTR on it!.