FarmerPotato

The F543 in DIP is much cheaper than my 651s at Rochester. The minimum buy is always $250 but you get them at $0.47. Alas for that $250 though.

'543s and all registered (latching) transceivers... I've spent a lot of time investigating these for NuBus. NuBus used a LOT of obsolete 651 types. The 646 types are still around. Does it really need the Fast part? F parts can be replaced by AS or ABT, not that that is any easier. (ABT from the 90s on is all surface mount.) Are you willing to do any design modifications? If so, it's likely that the 543 is overkill and can be functionally replaced with a 646, or a 645 plus two 573. I imagine the 543 is used to buffer a 16 bit data bus to 8? Like the console does with a 373 latch and 245 transceiver. This job doesn't fully utilize the 543. The 543 or 651 get used fully when two buses need full access to each other, and both have multiplexed address/data. check if any of the 543's functions were never used! That is, enable or clock pins shorted to GND or VCC.

Do you have a 928 to upgrade? Or just interested in the code (x86)? The internal ROM is 32K, about 24K used, in a OTP DIP32. The plug in module has a DIP28 8K, but in a DIP32 footprint. A PLD--I guess GAL22V10, to map address lines. I haven't desoldered it. Guess: the PLD overrides just the top 8K, but the slot might accept a full 32K. The slot is too small for socketed chips. I realized after I put a socket under the EPROM!

Yes, I have it. Was waiting for Jim to check if HCS minds.

FYI: the ROMs have been dumped successfully. I replaced the safety capacitors and the coin battery. The power switch toggles. The EPROM in its new machine pin socket kept popping out. So I flattened the legs. (They were in a bow shape, maybe an advantage in PCB thru holes.) Glued on a new foam protector for the electron gun. Reassembled the whole thing today. Alas. It powers on silently with just one bright horizontal green line. I have to learn some more about CRTs. Ideas seem to be DC power to the deflection coil. Or a service switch activated. A vertical gain IC. Or any type of loose connection. RetroTech video & comments

It would be awesome if you could demo to the Zoom club on Saturday-1 to 3 PM CST!

It's not vaporware unless you promise "releasing soon!" I'd love to see work in progress: graphics, animation, scenery. You can do a walkthrough narrative.

Ah. The datasheet says "embedded battery". Seemed like a stretch that they fit a battery inside the DIP8. (Even 45 mAh)

You know those BQ or Dallas Semiconductor clock chips? The ones with the integrated battery that dies with no way to replace it? Well here's the oddball DS1213B battery-backed Smart Socket. It has a little 8-pin controller chip that apparently *has the lithium cells in the chip package*. Two 45 mAh cells. RAM not included. Are they battery time bombs, like doomed goldfish? The data sheet says the cell does not power on until the first time you insert a chip. It's like they embedded the plastic pull tab, too! And it accepts either DIP24 or DIP28 RAM! 2K or 8K. Smart switching! (VCC pin can be on pin 26 or 28) The oddest thing I've seen lately. Datasheet eBay tvsat_electronic listing

I looked through some TI source code and (longtime TI-990 engineer) Dave Pitts' C runtime for 990. It is full of "@R1*2(R13)" type addressing modes. But no "@0(R13)". It seems like an unspoken rule that R0 shall not be used for parameter passing! I did not find any *R13 either.

Uh, right, those are "warnings". The constant folding, you ask for with # syntax in the addressing.

I agree with what you said. Automatic optimization would disturb me, if I looked at a dis-assembly in debug. (Though I mostly rely on List files.) Especially if it was a timed loop and you don't want it to get faster. There are a few optimizations that Ralph's xas99 can do. They can save a few bytes. Nice to know they are there, when every byte matters. (Things like: Replace B with JMP LI R2,-1 with SETO Share constants )

That's a good reason. I also see a lot of TI source code that does R2*2(R13) It seems that *R13 would be an easy optimization for an assembler to make.

The NE182UEE6AMP was not a great fit. For one, the switch body is shorter. 3 pins could be forced into the existing ME5A footprint, with the fourth pin necessarily jumpered. But then the actuator would be too short, and the mechanical support ring would not fit at all. We chose to put the NE18 switch on the existing retaining ring. That makes only a slight difference in actuator length. All 4 pins would be wired to the PCB contacts. But then Amanda asked why not turn the switch upside down? That is a much neater solution. 18AWG wire, crimped on the PCB end, plus shrink tubing. There is still exposed copper on top. While in there, we desoldered and socketed the ROM. Same for the HCS upgrade ROM. Both are now dumped. Jobs to do next: 1. Replace the foam bumper protecting the cathode. Before the foam rotted, it was held on with double-sided tape. 2. Replace two RIFA caps. 3. Replace the 2032 battery. It's the standard 3-pin type, with permanent contacts. But the PCB has another via, so it can accept either 2 pin or 3 pin. 20 mm distance between pins.

I'm glad your excited! I look forward to your help, too, cracking this nut. Also see the other thread and check out what Eric Lafortune has finished. I have had a particular person's voice in mind for a while. I started a Parsec-themed game (the setting is the Parsec moon), but left it to work on hardware. That's where I would put speech. By co-op multitasking -- is your C program polling speech periodically, or do you have co-routines, or something else? My code makes one loop around all the things that need attention, like the speech synthesizer or (my code for) sprite motion. Then it kills time waiting for the VDP interrupt, when it is safe to write to VDP. Worst case, 16 ms goes by, just like with a ISR. Enough to keep the speech synthesizer happy. (Sprite motion is actually pretty easy--2 bytes for X, 2 for Y--you add signed amount to the 2-byte coordinate, the upper byte goes to the sprite attribute table.)