"Bill Garber" writes: > Combining the 2 answers tells me that the hardware governs > whether a drive is working at 13 or 16 sector, and adding > everything else I have heard. Thanks everyone for clearing > that up. Specifically, with the Apple Disk ][ controller: The P5 (341-0009) and P5A (341-0027) PROMs contains 13- and 16-sector boot code, respectively. This determines which kind of diskettes can be booted directly, but does not affect which can be accessed. It is possible to boot software from a 13-sector diskettes that knows how to read and write 16-sector diskettes (but see the P6 notes below). For instance, there was a hacked version of MUFFIN, Apple's 13-sector-to-16-sector utility, that worked in the reverse direction. If you have a P5A PROM and want to boot a 13-sector diskette, you'll need to either boot the BASICS disk first, or boot DOS 3.3 and run BOOT13. The P6 (341-0010) state machine PROM can not read 16-sector diskettes reliably. It should only be used with 13-sector diskettes. The P6A (341-0028) can read both 13- and 16-sector diskettes reliably. There is no reason to use the old P6 state machine PROM, even if you're going to use a P5 13-sector boot PROM. On the other hand, installing the P5A and P6 together is asking for trouble, since it would only be able to boot 16-sector disks which it would be unable to read reliably. Of course, normally the PROMs were used in matching pairs. Controllers that were originally shipped with the P5 and P6 were generally upgarded to the P5A and P6A at the same time. Speaking of which, has anyone got any extra P5 or P6 chips they'd be willing to sell or trade? At the very least I'd be willing to provide a P5A and P6A if anyone needs an upgrade. Failing that, a copy of the P5 and P6 bit patterns would let me burn my own, assuming that I can find some blank 6309, 82S135, 82LS135, TBP18S22, 74S471, or 74LS471 PROMs. Back in 1980 I programmed a double-size PROM (512x8) with the contents of both the P5 and P5A PROMs, and wired the extra address line to a switch on the side of my Apple ][+. IIRC, the PROM was a Texas Instruments TBP28S42, though the 82S147, 6349, 7649, 74S472, or 74LS472 should also work. I had to write a little program to reformat the data because of the way the address lines are arranged on the larger chip. Eric [Remove obvious spam-proofing from my email address if you want to send a reply by private email.] In article , Eric Smith wrote: > >Failing that, a copy of the P5 and P6 bit patterns would let me burn my >own, assuming that I can find some blank 6309, 82S135, 82LS135, >TBP18S22, 74S471, or 74LS471 PROMs. I have two files called 'p5' and 'p5.scrambled'. I believe the former is the ROM code as it appears to the Apple and the latter is nearly as it appears on the ROM, except that the data line permutations are already taken into account. Unfortunately I don't have the original HEX-format listing (with the data lines partially reversed) nor the program to convert between them any more. They're short, so I'll post them. p5: 00: A2 20 A0 00 A9 03 85 3C 18 88 98 24 3C F0 F5 26 10: 3C 90 F8 C0 D5 F0 ED CA 8A 99 00 08 D0 E6 20 58 20: FF BA BD 00 01 48 0A 0A 0A 0A 85 2B AA A9 D0 48 30: BD 8E C0 BD 8C C0 BD 8A C0 BD 89 C0 A0 50 BD 80 40: C0 98 29 03 0A 05 2B AA BD 81 C0 A9 56 20 A8 FC 50: 88 10 EB A9 03 85 27 A9 00 85 26 85 3D 18 08 BD 60: 8C C0 10 FB 49 D5 D0 F7 BD 8C C0 10 FB C9 AA D0 70: F3 EA BD 8C C0 10 FB C9 B5 F0 09 28 90 DF 49 AD 80: F0 1F D0 D9 A0 03 84 2A BD 8C C0 10 FB 2A 85 3C 90: BD 8C C0 10 FB 25 3C 88 D0 EE 28 C5 3D D0 BE B0 A0: BD A0 9A 84 3C BC 8C C0 10 FB 59 00 08 A4 3C 88 B0: 99 00 08 D0 EE 84 3C BC 8C C0 10 FB 59 00 08 A4 C0: 3C 91 26 C8 D0 EF BC 8C C0 10 FB 59 00 08 D0 8D D0: 60 A8 A2 00 B9 00 08 4A 3E CC 03 4A 3E 99 03 85 E0: 3C B1 26 0A 0A 0A 05 3C 91 26 C8 E8 E0 33 D0 E4 F0: C6 2A D0 DE CC 00 03 D0 03 4C 01 03 4C 2D FF FF p5.scrambled 00: A2 20 A0 00 A9 03 85 3C 18 88 98 24 3C F0 F5 26 10: 3C 90 F8 C0 D5 F0 ED CA 8A 99 00 08 D0 E6 20 58 20: F0 1F D0 D9 A0 03 84 2A BD 8C C0 10 FB 2A 85 3C 30: BD 8C C0 10 FB 25 3C 88 D0 EE 28 C5 3D D0 BE B0 40: C0 98 29 03 0A 05 2B AA BD 81 C0 A9 56 20 A8 FC 50: 88 10 EB A9 03 85 27 A9 00 85 26 85 3D 18 08 BD 60: 3C 91 26 C8 D0 EF BC 8C C0 10 FB 59 00 08 D0 8D 70: 60 A8 A2 00 B9 00 08 4A 3E CC 03 4A 3E 99 03 85 80: FF BA BD 00 01 48 0A 0A 0A 0A 85 2B AA A9 D0 48 90: BD 8E C0 BD 8C C0 BD 8A C0 BD 89 C0 A0 50 BD 80 A0: BD A0 9A 84 3C BC 8C C0 10 FB 59 00 08 A4 3C 88 B0: 99 00 08 D0 EE 84 3C BC 8C C0 10 FB 59 00 08 A4 C0: 8C C0 10 FB 49 D5 D0 F7 BD 8C C0 10 FB C9 AA D0 D0: F3 EA BD 8C C0 10 FB C9 B5 F0 09 28 90 DF 49 AD E0: 3C B1 26 0A 0A 0A 05 3C 91 26 C8 E8 E0 33 D0 E4 F0: C6 2A D0 DE CC 00 03 D0 03 4C 01 03 4C 2D FF FF -- Matthew T. Russotto mrussotto@speakeasy.net "Extremism in defense of liberty is no vice, and moderation in pursuit of justice is no virtue." But extreme restriction of liberty in pursuit of a modicum of security is a very expensive vice.