S-JIFFYDOS 1541 (SJD41) is a CBM 1541 floppy DOS operating-system, that works in a 1541 in an eprom. It is a patch for JIFFYDOS 1541 (JD41). But don't be afraid, nobody must renounce for the original JIFFYDOS; this instruction describes, how You build CBM-, JIFFYDOS- und S-JIFFYDOS simultaneously into all three versions of the 1541 (old, /c, /2). Because it's a patch for JIFFYDOS 1541, the patch program doesn't work without this at all. It uses the original JD IEC bus routines, so it works with all (only-CBM-) and JIFFYDOS-computers and -speeder- cartridges. It reaches with all JD- computers and -speeder-cartdriges the below spezified speeds, that means, that You don't need SJD64 in Your C64. SJD41 and SJD64 are absolutely independent.

Here are the speeds of S-JIFFYDOS1541 (in compare to CBM1541 and to JIFFYDOS1541):

                                  CBM1541 JD1541 SJD1541
new/format 35 tracks                95,4    22,2    22,5
load 202 blocks (at gap)           127,2    13,2     8,7  
                                  (9,5)     (6)     (4+)
load 202 blocks at gap 9,5         127,2    20,7    14,7
save 154 blocks                    105,3    43,4    21,0
scratch 202 blocks                  24,9    14,9     4,3
scratch 664 blocks 144 files       361,7   260,3    17,9
validate 664 blocks 144 files      239,0   139,6    10,9
search the 144th file in dir         5,3     4,7     1,1
100 bytes IECOUT                  0,146   0,0335  0,0335
100 bytes IECIN                   0,204   0,0216  0,0216
- can use 40 tracks: first @"et+ (return), then @"n:dn,id (return) (!news the disk!)
- @"el @"eu lock/unlock of files. Advantage to JD: You can use several files by using jokers
- @"el:$ @"eu:$ lock/unlock of disk
- @"v validates GEOS disks correct
- @"vg- validates normal (GEOS disks wrong)
- @"sg+ scratches GEOS VLIR files correct
- @"nv- news a disk without verify
- @"e extended floppy status (+ is on, - ist off)
. 02,sj+ ic+ dt- mb- em- .tk.gp,35,00
. sj = S-JIFFYDOS on/off
. dt = allows/forbites the writing of files (not of the dir) onto the dir track 18. Before using blocks on track 18, SJD allocates the dir blocks in the BAM to be on the sure side. The dir can always be written onto track 18 (independent of DT). The advantige of DT is, that if a disk has not enough free blocks to save a file on this disk, then You can write this file onto the free sectors of track 18 (these are usually reserved for the dir and can't be used of normal files). This is sometimes a possibility, to save the last file on a disk. !There is the danger of loosing datas by using dir- editors!
. mb = mechanical bump = hard-CBM- / allmoust soft SJD-bump
. em = execution of MB = MB allready / not yet made (only if MB-) (MB and EM are for internal SJD41 routines. You needn't change here anything)
. tk = 35/40 tracks
. gp = gap, interleave (00 means, that SJD41 uses the optimal gap)
./! = track automatically (depends on disk-ID) / fixed
- @"es+ switch on SJD mode
- @"ei- switch off JD-IEC-bus routines
- @"e+ default for ON
- @"e- default for OFF
- @"et automatical track recognition: recognizes a 40 track disk at " 4a" or " 4<"
- @"et+ fixes 40 tracks
- @"et- fixes 35 tracks
- @"eh:dn,id changes disk-name and ID
- @"e changes the device number
- @"ec checks a disk for bad blocks
- @"eca+ check&allocate checks a disk for bad blocks and allocates them in the BAM
- @"ec (number (1-41)) checks, starting with track
- special LOAD routine for PRGs, that are saved with the CBM gap 9,5
- special LOAD routine, that decodes from the GCR bytes to HD format, while reading the bytes from the disk. Uses gap 4
- the area c000-dfff has (allmoust) all patches of the 1541/2 DOS, consequently also the repair of the save&replace bug (At the 1541old only if both eproms are changed)
- fast open uses gap 3 instead of 22
- the error channel prints the error numbers with three positions, if the error number is greater than 99.
- fast reset without RAM and ROM test
- drive 1 (allmoust) never occupies an unneccesary buffer
- fast save: Because SJD41 must use the original routines of the C64, and because at theese routines the IRQ isn't prevented, You schouldn't press any key during the save. Otherwise the IRQ of the C64 would be longer than the 1541 thinks and the save would be a little bit slower. Fast save verifies the written blocks, that means the speed isn't at cost of the data- security.
- fast-scratch und -validate makes the checksum while reading the bytes from the disk
- if You change only one eprom at the 1541old, then You don't have check, fast-lock/unlock, -scratch, -validate and -save and the 1541/2 bug-patches
- SJD uses the area 8000-ffff (At the 1541/c and /2 always; at the 1541old only if both eproms are changed (1541old and only one changed eprom: a000-ffff))
- SJD41 has the same IEC bus routines as JD41, that means it schould work with all CMD-computers and -speeder-cartridges

More informations at http://home.t-online.de/home/dadler

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Jochen Adler
Haeldestr. 9
D-74912 Kirchardt