Currently I'm developing the stepper motor driver routines to be able to access all tracks (and not only track 00). I'm now in the 7th week of writing and debugging the RWTS on the real hardware and so far it can read sectors and format a track, and it works well. If yes, would not it make sense to add an EPROM or PROMs to the PCB? On the 1st April thread we can see you start a (test?) routine located at $0600 that seem to load a predefined set of sectors. This would be an entirely different animal. But you need to solve the power supply issue, too. You could try to get an IWM chip and make a small PCB for it. So what can you do to add a floppy disk system to the Replica-1 ? Designing this DC/DC converter probably is the most difficult part in this project. My desire to use only "period correct" parts is compounding the problem.
I have an idea on how to make +12V from the unregulated -22V and +22V on the Apple-1 44-pin bus, but this requires a switchmode DC/DC converter topology for which no ready made controller IC exists. On the Apple-1 I can easily provide -12V and +5V but the +12V has to be fed in externally (this is the little header between the 20 pin disk drive connectors). This is why Apple (the corporation) had to develop the "Integrated WOZ Machine", or IWM, for the Apple-IIc which uses a 65C02.ī) the floppy disk drives need -12V, +5V, +12V supply voltages.
The "Woz Machine" in its original form requires the phantom read to work and this is not a cycle count issue, the problem roots deeper. There are two reasons:Ī) the CMOS 6502 (all of them) do not have the "phantom read" in the STA abs,x instruction execution which the original NMOS 6502 have. Sorry to say my Disk-1 controller is meant for the Apple-1, originals or clones, and not for replicas. Wonderful job, would be fun to try it on the Apple Replica I Try it ! Uncle Bernie's riddles always are fun ! Life without riddles to solve would be boring ! You can also guess the title of the movie.
Here is a hint: there is a movie about a close relative of this device having the same acronym but not exactly the same name. P.S.S.: Another riddle for you (I'm the "Riddler" although I like "Iron Man" more): guess what the "TFC" stands for. This is why I use them for the development work. But unlike PALs, GALs can be edited to make changes to the logic within. The GAL16V8 is based on EEPROM CMOS technology and came out in 1985. these are only used to emulate the precious and horribly expensive bipolar PAL16R4 and PAL16R6, which are very rare nowadays. Do not get distracted by my use of those GAL16V8. Apple released their Disk-II system for sale 4 months later, in June 1978. But technically, the PAL killed them dead. It was a game changer ! TTL and LSTTL became obsolete over night, technically, but not commercially, since they had a market momentum too large to die out quickly. MMI reveiled the PAL to the public in March 1978. P.S.: for the "purists" among us: only using year 1978 "period correct" parts was an imperative requirement in my Objective Specification for this project. The more responses this thread gets, the higher the chance that I don't just shelve this project after I have completed the RWTS.
True "Magic" !Īny interest / questions ? - Feel free to ask and post your comments in this thread.
The "TFC" makes all the trouble with the stolen CPU cycles go away, like a Stage Magician makes all sorts of things, animals and even beautiful girls disappear in front of your eyes. And the "TFC" is where the magic happens to make the whole thing work under the constant barrage of non-transparent DRAM refresh cycles, which steal CPU cycles and break Woz' original concept based on precise CPU cycle counting in all the timing critical RWTS routines.Īs far as I can say 6 weeks into the development of the new RWTS routines, it does work, and it does work reliably. These additions are necessary because the Apple-1 does not have a 2 MHz "Q3" clock on its bus, which clocks the Woz Machine, so the "Clock Generator" makes a substitute from the 1 MHz system clock. These are the Apple-1 specific additions I had to make:ħ4LS132 (1/2 of the IC), 74LS123 - "Clock Generator" These are the parts functionally identical to Apple's Disk II card:ħ4LS74,74LS299,GAL16V8/PAL16R6 - "Woz Machine"