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FarmerPotato

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About FarmerPotato

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    Moonsweeper
  • Birthday 01/01/1971

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  • Gender
    Male
  • Location
    Austin, TX
  • Interests
    TI-99/4A. FORTH. Verilog.
  • Currently Playing
    Last year: Port Royale 3, Pocket Trains, Minecraft, Master of Orion II, PacMan 256, Katamari Damacy, We Love Katamari, NY Times Crossword
    This year: Katamari Damacy Reroll, Settlers of Catan Universe, Chisholm Trail, NY Times Crossword

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  1. It's almost the 3rd Wednesday work night at ATX Hackerspace, Jul 16. I'll be there doing some 99/4ATX business. Like trying out video conferencing in the classroom, with YouTube and Zoom. In case you want to test being on the Zoom channel, here's the URL: Zoom meeting URL: https://zoom.us/j/7707370625 I'm not sure if you have to sign in on Zoom. Anyway its free. YouTube test channel to follow. Anybody is welcome to jump in Wednesday night after 7:30 Central. Thanks for all the input on which videoconference.
  2. I'm in the 24hr wait period for YouTube. I like Zoom and it has chat and screen sharing. It turns out it only costs $15 for a one month plan. The free one cuts off every 40 minutes. My new Zoom meeting URL: https://zoom.us/j/7707370625
  3. Has anybody made (for sale) a test point adaptor for Pbox card, sidecar, or cartridge port? I've seen pictures of a Pbox card riser with a card on top. Ideally there would be a row of pin headers to attach probes to, so that you can watch the bus without adding test points for all the common signals to hardware under development. I drew up a PCB for the cartridge port, 3" long and 2" wide (just a bit wider than the 2x18 card edge.) It takes a 2x18 header for test leads, and a pass-thru 4A cartridge port (either pointing up, or reuse the right angle adaptor.) I'm kind of balking at the fab cost which is the same as a regular cartridge run. Ideas to make it more useful would be to squeeze in some pads for GROM, EPROM, bank latch, and maybe even a tiny prototype area. So it becomes both a cartridge debugger AND an experimenter board. Test points board. 50mm wide x 75 mm long. ||||||||||||||| -|||||||||||||||- ||||||||||||||||| ||||||||||||||||| ||||||||||||||||| ||||||||||||||||| ||||||||||||||||| |***************| test point |***************| headers ||||||||||||||||| ||||||||||||||||| |@@@@@@@@@@@@@@@| cartridge port \@@@@@@@@@@@@@@@/ pass-thru Experimenter add-on board. 50mm wide x 100mm long. ||||||||||||||| -|||||||||||||||- | | |LLLLLL GGGGGG | LATCH and GROM socket |LLLLLL GGGGGG | | | |RRRRRRRRR | EPROM socket |RRRRRRRRR | |RRRRRRRRR | | | |***************| breakout all pins |***************| in rational order |...............| protoboard |...............| |...............| . . |...............| |...............| |...............| Two boards can be panelized in a 100x100mm job ($16.95 at dirtypcbs.com), two for the price of one. Here's another inspiration for an experimenter board: https://store.digilentinc.com/breadboard-expansion-with-mxp-connectors-for-ni-myrio/
  4. I will try YouTube. There's no two-way there, no chat room right?
  5. Video Broadcast for 99/4ATX on weekend of Aug 8-10! We will have a Ustream channel. When no one wants to broadcast on it, it will point at something interesting, like a computer demo, a 3D printer, or a breakfast taco. You never know! https://www.ustream.tv/channel/u45p8uc7YSS I picked Ustream because the free trial seems better than freeconferencecall.com or Zoom.
  6. Making the RAM fast and large is a perfectly fine goal, it's just not possible on the cartridge port. 9900 doesn't need cache because its clock is only 3 MHz and cheap SRAM even from the late 80s needs no wait states. Cache is a necessity when your CPU is clocked way faster than the RAM; today your x86 is clocked in gigahertz and your RAM at 800 Mhz. TheBF had some good ideas about replacing the side port with a 16 bit fast memory bus to the PBox (I hope with a backwards compatible adaptor as an option). Others have put fast 32K memory inside the console. We don't need a cache, we just need RAM in the console that is 16 bit and no wait states. Modern SRAM is fast and cheap. For instance, this 512Kx8 thru-hole SRAM is $5 and is the type used in SAMS cards (and hopefully future Horizon RAMdisk). And this 512Kx8 or 256Kx16 part is $3 and $5, operates up to 100Mhz, and comes in a surface mount package that is just a little harder to solder than plain old 0.1" thru hole chips (SOJ-36 with 0.05" pins, you need a magnifier, and a knife edge K solder tip.) It would be hellacomplicated but you could make an in-console 16-bit bus tiny SAMS upgrade around that. Then again, I have more ideas than time or attention span.
  7. I'm still waiting for the actual cart boards from DirtyPCBs (where they cost $2 each). I held it up until I added the peg hole into the board (oops). BUT I will have this test rig for the ATF22V10 logic chip from OshPark next week. I couldn't stand working with the PLCC to DIP adaptor that came with the TL866 / XGecu programmer. (It doesn't fit a breadboard, for one.) It it a PLCC-28 adaptor with two sets of pins: one set on the bottom plugs into a breadboard, while the top set is for a logic analyzer. All the pins on top are labeled. Carts through OshPark would cost $50 for 3! It's good for prototyping small things fast at $5/sq inch for three samples. (I screw up one while soldering, I get the next one working, maybe need the 3rd one after I break #2.)
  8. I think that considering a 512K flash cart as a big RAM is off the track. You could replace the chip with a large SRAM (for about $20) and have a mega-Supercart, but here are the numbers, like mizapf said: Relative Speeds (not including instruction overhead which is pretty big.) 1 PAD 16-bit access in 1 cycle each for read and write. 6 32K expansion 8-bit access in 6 cycles for read and write of 1 or 2 bytes. 2 x (1 cycle + 2 wait states). 6 times slower than PAD. 300 Flash - same read access as 32K, but takes 9 writes to program one byte. Plus a lot more instruction fetch and executes. So it will be at least 20 times slower than the 32K RAM per byte, or 40x slower per word. I'm guessing 50x after overhead. In other words, writing to Flash is best suited for saving small amounts of data or loading a new cart into the thing. I spent a lot of hours with the logic analyzer on the side port watching Mini Memory and 32k accesses. I know it pretty well by now. Tursi also made a great document from his logic analyzer of all types of memory cycles. I'll record the bus activity of the flash-writing code listed above to know for sure what the relative speed will be. (I have simulated my tests so far in the WinCUPL simulator from the Windows 95 era and I really, really have grown to hate it.)
  9. OK. We have a really nice Hakko desoldering vacuum gun and ChipQuik. Makes it a breeze. Bring a 40 pin socket.
  10. We can get one out of a scrap 4A for you. Otherwise it's about $3-$5 from China, $30 domestic. I forget whether it's soldered or socketed, but no problem, we can desolder at the Hackerspace.
  11. I think you described that you disconnected the keyboard, and touched pins together to mimic keys pressed? In that case most likely the 9901 chip is bad.
  12. You just made my day. I missed this whole thread before!
  13. Oh crud, my brain just worked out a possible harebrained scheme to keep the >6000 space locked to the first 4K (bank 0) while allowing the >7000 space to map any bank (7 bits). That means many hours more of simulation and testing... NOOOOO! It's not possible to give the bottom 4K the ability to switch in some different banks. This would be a choice at the time the ATF22V10 logic is programmed: regular 8K banking, or fixed 4K + banked 4K. Such a scheme would allow the programmer to have all the library code in bank 0, plus the main program loop, calling lots of subroutines in the other banks. The file system code would execute from bank 0 and use the upper 4K to map in the storage space. Just to re-clarify, this cartridge is not a general-purpose storage device. The program inside it would have to be written specifically to use it.
  14. Answering your questions in order: I think a regular DSR is too complicated to adapt. Cartridge ROM is not searched by the usual DSRLNK? Accessing it in the cartridge space is tricky. I have read the source though and I think the Horizon DSR is excellent. I would like to use it on a sidecar. The 512K Flash chips are as big as it can go. The next size up, 1024K, is not compatible with 5V (3.3V only), costs $5, and doesn't come in an easy to solder package. See Tursi's Dragon's Lair cartridge for an example of surface mount Flash, 1024K I think. Novice soldering skills must be enough, so no surface mount, only thru-hole. My cart is not intended to be like FinalGROM, for one thing it's not capable of doing GROM. FinalGROM uses a proper FPGA to do all the emulation. UberGROM uses an ATmega128 microprocessor to emulate GROM, which is a pretty good low-cost solution. My cart just has a cheap logic chip with 10 bits of memory. My goal is to make the lowest cost multi cart out there (now $8) but still distinguish it from the old 512K multicart by adding save capability. This design is locked down now (lots and lots of hours put into it...) Upgrading the logic to have 20 or 32 bits is beyond reach. The cheap XGecu programmer doesn't support these chips: ATF750 or ATF1502. Newer logic chips are not easy to solder. Aside: I'm operating outside the usual path by skipping Xilinx FPGAs that everybody else has used. I'm a sucker with an emotional attachment for the underdogs. (Sound familiar?)
  15. Also, if your registers are in PAD (e.g. >8300) then arguments in registers save a lot of cycles. Fetching the address from 8-bit memory costs 6 cycles after wait states, but fetching a register is 1 memory access. * Really fast code assuming registers in PAD LI R9,GADR STWP R0 INCT R0 * set pointer to R1.. could be LI R0,MYWS+2 or LI R0,>8302 MOV *R9+,*R0+ * copies to R1 MOV *R9+,*R0+ * copies to R2 MOV *R9+,*R0+ * copies to R3
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