Recent content by quorten

Interesting that there are revisions of the Plus boards that use the same TSM that was designed on 512k. I thought I mapped out the difference between the two TSM variants and it is relatively trivial... but I'd have to revisit. This is definitely the board I would need for testing the...

@Kai Robinson I'm pretty sure the only reason why the Mac Plus inverts the clock signal is because that must have appeared to be the most convenient chip-saving layout. Good to know it is the Sony SND chips that's responsible for generating the power-on-RESET signal.  I believe the interesting...

Mentioning bodge wire and unconnected traces that shouldn't affect signaling... well that's one thing that old and slow computers are quite a bit more forgiving on!  If I've read the schematics correctly, though, the Macintosh SE does in fact use some impedance-matching resistors for certain...

I'd guess probably the most useful thing from @timdorez's tech manuals is the troubleshooting info, seems like the other schematics are largely the same as what currently floating around but always worth taking a more detailed look! Nice find on the Bomarc Macintosh SE schematic...

The idea is to go for a flat-panel that caters to the traditional market served by PVM (Professional Video Monitor) CRTs, so you might search around for "security" or "industrial" monitors.  Such displays have separate sync signals for RGB component video and are probably more forgiving to...

How about something like the Walk-a-Mac?  TTL-input video flat-panel displays are available under the names of "security monitor" or similar, then you just need a logic NOT chip to get the proper input video signals.

@Kai Robinson Interesting idea on setting up the layout of the data.  Probably the circuit board footprint of the BBU's socket would be generally more useful when working with the hardware, though (of course not much different).  I would recommend sticking to the Apple terminology that I've used...

Interesting, I have to say I was somewhat surprised at first to hear that New-Old-Stock apple custom ICs are actually a thing.  But I'm guessing it makes sense if you think a bit deeper... Apple may have been planning on making extras on the assumption that their techs might do precise, minimal...

No problem @maceffects, probably better that your meandering mind touches some points before other's do.  Good to have the discussion, as long as we do not feel things are getting too chatty/cluttered here. Almost anything is possible with bank switching.  The main limit is really what can be...

@maceffects It's also useful to reflect upon Brainstorm's historic business model, which was to first reverse engineer the Macintosh Plus PALs and then use that knowledge to create the Macintosh SE BBU replacement.  I'd reckon that method on its own must have created pretty good results.  As far...

@CharlesT The BBU has an internal soft switch for the ROM Overlay signal, which remaps the ROM to address zero on reset, and the RAM is likewise remapped.  It is disabled on the first regular ROM access.

@maceffects Sure, my GitHub repository for my leg of the project seeks to be a useful reference repository that links to all the pertinent information.  A lot of the essential information should be copied in and covered there.  I'll be updating it with a few more links shortly but it is pretty...

@Kai Robinson Honestly I think much of the new interest here needs to spend some time to review some of the existing documentation we have before we can get much progress on a zoom call.  Really, there's not much hidden info remaining after my analysis thus far, I just feel that no one has yet...

It really isn't hard to adapt the original BBU design to support a 16 MHz CPU.  I'd guess the purpose of the drivers is primarily to support a soft switch for "turbo" in case you want to run at the normal speed.  I must admit that the back side of that PDS circuit board is quite funny looking...

The problem could be that RESET is not held for long enough for the processor's internal state to stabilize.  According to the MC68000 User's Manual, page 10-12, note 4: "For power-up, the MC68000 must be held in the reset state for 100 ms to allow stabilization of on-chip circuitry. After the...