Someone asked:
How can you tell about the original ROMs and 13 sector
disk?
Sellam wrote:
Usually, ROM-D8 and ROM-D0 will be missing. In the
two that I have here,
one has both ROMs missing, but one has the D0 ROM. The copyright's on
mine are 1978, so I don't know exactly what that means. I would guess the
originals would have a copyright of 1977, but these are definitely Apple
]['s and not ][+'s.
The part numbers on the ROMs are the only sure check, and I don't have them
handy. I think they are all 341-xxxx part numbers.
Anyhow, the F8 ROM is the monitor. The Apple ][ shipped with the original
monitor, and the ][+ with the Autostart monitor, but some Apple ][s may
have been retrofitted.
The E0, E8, and F0 ROMs are present for Integer BASIC (which also includes
the mini-assembler). In a ][ (or an Integer BASIC card), the D0 ROM socket
is sometimes occupied by Programmers Aid #1. AFAIK Apple didn't offer
any other option ROMs for the D0 or D8 socket, but there were some third-
party option ROMs. ISTR a ROM called Watson that went into D8 and provided
disk and memory editing features.
Applesoft ][ ROMs take up all five of the non-monitor sockets, i.e.,
D0, D8, E0, E8, and F0.
One can conclude from this that an Apple motherboard or ROM BASIC card
with less than the full six slots occupied either has Integer BASIC or
an incomplete set of Applesoft ][.
A motherboard or ROM BASIC card with all six slots occupied probably
has Applesoft ][, but there's some chance that it's Integer BASIC with
option ROMs.
I'll bet Eric Smith knows this (as well as how to
properly identify a
13-sector disk controller...one clue is that it is missing the sticker
that has the Apple logo with a "16" inside, but that isn't a reliable
indicator).
A 13-sector controller's PROMs are labelled P5 and P6, whereas a 16-sector
controller has P5A and P6A.
It is reasonable to upgrade a 13 sector controller to P5 with P6A. This
retains the 13-sector boot code, but upgrades the state machine to be
capable of reading 16-sector format. In my machine I had two controllers,
one with P5 and P6A, the other with P5A and P6A. I would boot 13-sector
disks from the former and 16-sector from the latter, but when 16-sector
software was running, it could use all four drives.
On a controller with the P6 ROM, it is sometimes possible to read 16-sector
diskettes, but it's unreliable and usually requires many retries. The
P6 PROM is technically capable of writing 16-sector format, but since
writing a disk sector requires reading the sector header, in practice
that can't be done reliably either.