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Gorgonops

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  1. Gorgonops

    Question: 128k/512k and 800k drive

    Then you should be good good to go. I probably should have mentioned that myself since I have first-hand experience that my 512k-no-e can boot from a IIgs drive connected externally.
  2. Gorgonops

    Question: 128k/512k and 800k drive

    Yes, that particular drive works because Apple did some "magic" the tach signal that sidesteps the bug in the 64k ROM. The internal 800k drive mechanisms (or the "original" Mac-styled 800k drive) are the ones with the problem.
  3. Gorgonops

    Question: 128k/512k and 800k drive

    The IWM isn't a problem, but the ROM is. To make a long story short trying to use an 800k drive with the original 64k Mac ROMs results in a divide-by-zero error because a bug in said ROMs gets triggered if there isn't a constant slight variance in the tachometer readings, which the 800k drive doesn't provide. (Remember, the 400k drive's speed was directly controlled by a PWM signal generated by the Mac and adjusted based on tach feedback, while the 800k drive self-regulates its speed based on what track the head's on.) You could slap a set of Plus ROMs into the boards for testing, if need be. That essentially would temporarily convert them to 128ke(an unofficial designation for such a Frankenstein)/512ke's that are fully compatible with the 800k drive.
  4. Gorgonops

    MAC SE/30 with orange colored CRT

    One thing to be careful of if you sub a green or amber CRT into a Mac is the longer persistence phosphors in them are somewhat more prone to burn-in than the white TV phosphor the Mac came with. Probably not a big deal considering how much use a toaster Mac is likely to get in the real world today, but definitely consider turning the brightness down if you walk off for a while. Unless the Mac had other specific "Tempest" modifications there really isn't a lot of reason to suspect the military was involved in the CRT swap, but it is at least *possible* that it was swapped because of some government requirement that machines purchased for some agency meet some ergonomic standard; the selling point for those colored CRTs is their longer persistence phosphors reduced flicker and, therefore, reduced eyestrain. Langley-St. Clair was mentioned earlier as a vendor that sold alternative CRTs for various computers, I'm vaguely curious if they ever advertised in a Macintosh magazine. The CRTs themselves weren't "special" and were used in many portable computers; the original Compaq portable used green, but as noted the IBM 5155 used amber, and amber was an option on the later Compaq Portable II and scads of others, including bargain basement knockoffs.
  5. I didn't see this answered earlier, I apologize if I'm blind. Asterisks like that usually mean "active low". (IE, the line is pulled to zero to activate the named function. This is usually the case for chip selects. Not universally so, but usually, because TTL process chips in particular tend to float to "1" if they're left disconnected so it's the slightly safer choice.) Another common convention is to put a /slash in front of the name.
  6. Gorgonops

    Apple Lisa Twiggy/FileWare Disk Recreation

    So, yeah, there you go, HD media is the correct choice. The Twiggy just sort of sucks at using it.
  7. Gorgonops

    Apple Lisa Twiggy/FileWare Disk Recreation

    HD disks are utterly hopeless in drives like the C1541 (and Disk II/TRS-80 Whatever/IBM 5150/etc), the magnetic coating on them is far too stubborn for the pipsqueaky powers of a double-density head. On the other hand, my recollection is that according to "those who know" the magnetic coercivity of the Twiggy was either identical to 1.2MB floppies or at least closer to it than double-density media, so of what's available it's the better choice. Honestly I kind of wonder about the recommendation because, frankly, the capacity of the Twiggy isn't that great. They sold "Quad Density" drives that formatted conventional DD disks with 80 tracks of 96 TPI track spacing instead of 40@48 TPI and the resulting capacity was similar to that of the Twiggy and it was achieved without playing games like varying the disk speed. (Commodore sold a disk drive called the 8250 for the PET series of machines that actually got *more* on a disk than Twiggy using conventional DD media formatted in a GCR format that similarly packed more sectors on the outer tracks, but did it by varying the data rate.) It might be an interesting experiment to mod some DD media and see if the HD media actually does work better.
  8. Gorgonops

    Macintosh Portable SRAM card: Schematics available?

    I had one of those Radio Shack Science Fair 150-in-1 things with the springs when I was a kid, that's probably my most relevant qualification.
  9. Gorgonops

    Macintosh Portable SRAM card: Schematics available?

    That's the important part. Isn't the GAL's fault that this board has that ridonkulous number of RAM chips. If you had fewer larger ones it'd do the job all by itself.
  10. Gorgonops

    Macintosh Portable SRAM card: Schematics available?

    Yay! GALs are truly magical.
  11. Gorgonops

    Macintosh Portable SRAM card: Schematics available?

    There's a number of weird things about PCBWay's pricing model. Their 10 for $5 is a helluva deal as long as your prototype is under 100mm in any dimension, but the pricing takes a huge leap if you exceed that. My most recent project was 100x150 mm and five boards from PCBway at that size gets quoted at $34. JLCPCB was only $9.10 for five so I gave them a try this time and so far their boards seem to be of roughly equivalent quality. I do think both companies are *really* hoping to bait you into using their manufacturing services. I'd be tempted because the prices for whole items don't really seem to be that bad, but their in-house parts catalog seems to be kind of thin when it comes to 5v legacy compatible devices.
  12. Gorgonops

    Macintosh Portable SRAM card: Schematics available?

    The original code I wrote only enables OE and WE based on the opposite state of the RW output lines from the bus: There shouldn't be any circumstance under which it would enable both at once unless there's some internal delay in play here since RAMOE is dependent on the feedback from MEMCS. (/MEMCS would be the equiv of your /154_OE.) The weird thing is if it *was* glitching on a feedback delay it should also be glitching on all the other lines that depend on it. (745OE and the two WE lines.) Your code looks like a pretty straight translation of mine other than it looks like we reversed the required state for AS. (Maybe I had it backwards, always possible.)... Actually, wait. I see that you're not bothering to test to see if the /UDS or /LDS lines are low before enabling OE. Is it possible that "RW" isn't stable if neither UDS or LDS is selected? (My code enables if either is low because enabling if both were high would be weird; that'd be the CPU asking to read memory from neither 8-bit bank.)
  13. Gorgonops

    Macintosh Portable SRAM card: Schematics available?

    I think I'll get away with having my bodge on the bottom where no one can see it. There's a via I can drill out to make the fix routeable on the dark side. When you get things so you can actually plug it in I guess we'll find out if /DELAYCS is actually a needed part of the equation. I do get a bad vibe that every manual on the Portable doesn't entirely correctly say what it's for, a suspicion bolstered by how they thought it was fine to ditch it on the backlight portable for something else.
  14. Gorgonops

    Macintosh Portable SRAM card: Schematics available?

    So I guess we're even on forgetting to add traces. I was testing the last untried section of my uberboard last night, the EMS page flipper, and found it was completely fouled up. (It looked like pages were being shuffled around essentially at random. I was able to confirm this was what was actually going on by sic-ing my ancient 80's logic probe on it.) Long story short, I completely brainfarted and forgot to route /IOW to the GAL and use it as part of the enable equation for writing to the paging registers. The mistake was sort of understandable because everything else I was decoding had "chip enable" lines and separately watched the system read/write signals, the paging registers were unique in needing a single enable/write strobe, but I am still kicking myself because my initial sketches had it right. Added a jumper wire between the missing signal and an extra input on the GAL and it works, but I am disappointed; I came *this close* to getting a first-run board that needed no bodge wires.
  15. Gorgonops

    Macintosh Portable SRAM card: Schematics available?

    I couldn't get CUPL to run on Windows 10 at all without crashing. Futzed around for hours trying to install ancient runtime packages and nothing helped. Last week because I'm apparently a stupid glutton for punishment I actually did get it working on WINE, it seems to work fine on that. I tested it out by translating my board's memory decoder GAL program to CUPL and succeeded in getting it to generate a .jed file, but for now I'm sticking with GALASM because I can run that anywhere and I'm not sure CUPL really adds a lot of value for a simple decoder. (It is *kind* of cool that you can set up the translation equations so you can test against human-readable addresses, but it's simple enough to just fire up a HEX to Binary calculator and sic it on your address; whether a bit position is a 1 or a 0 translates to if you /negate it or not.) Haven't had the patience to try to figure out the simulator in CUPL yet, that's what I use my arduino binary counter setup for.
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