Notices by Tube🌞Time (tubetime@mastodon.social), page 7

trying to capture more of the drive image to a binary. we'll see how it goes.

well now i feel a bit stupid. this thread from a few years ago includes links to disassembled drivers and ROMs, as well as a sample disk image.

https://eab.abime.net/showthread.php?t=89982&page=2

so even though this disk image is probably irrecoverable, i want to learn as much as a can. this drive was from the Amiga Comspec, and i want to see if i can figure out how to replicate the disk layout. this segment here is from the Kickstart disk.

anyway this analog signal comes off the drive's analog test points (circled). this signal comes after the differentiator (IC 9E1) and the first stage analog filter, but before the second stage filter.

not all the surfaces have a good amplitude. this could explain some of the issues i was having. (channel 2 has a pulse whenever the head changes.)

i decided to try and get a better read of the firmware tracks (-1 and -2 on all the heads). this time i'm capturing analog data from the drive's test points.

well that was easy!

going to dump the drive firmware for the ST-225N's 8051 microcontroller. this has never been dumped before. this firmware reads additional firmware off the platter, but i've already dumped that data.

i'm trying to correlate the drive's data output (valid on the rising edge, each pulse has a fixed width) with the analog data. it seems to have a delay of about 180ns caused by the analog filter and the propagation through the comparator.

it spins up and i've captured the negative tracks! (the Marker bit is a signal pulsed by the Arduino when it changes tracks or heads. it just cycles through all the heads in order, then goes to the next track)

just have to move this hacked up ST-225 logic board over. it's cabled to an Arduino that runs the stepper motor so i can get to the hidden tracks.

i've got another ST-225N to try and extract firmware from. the board was apparently dead, but eventually i might try it out with my other ST-225N logic board (i hope it still works)

and we've got copyright text at track -1, head 0, sector 0.

track -1, head 0, sector 19 contains the drive serial number as ASCII text. interesting.

looks like this came out of an Apple system. this is on track 0 which is user data.

track -2 contains the same 32 sectors on all heads. it seems to be 8051 code (02 is the LJMP instruction). i'm guessing this is the main drive operating code.

question: you have a USB connector on your project. how do you connect the shield? justify your answer, reply to the thread. (click this thread for the poll)

another early morning electronics flea market here in silicon valley (West Valley College). we're so early the sellers haven't arrived yet.

TDS 420. smokes when powered on

oh cool an Intel 286 design kit!