[HN Gopher] pico9918: A replacement TMS9918A/TMS9929A VDP using ...
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pico9918: A replacement TMS9918A/TMS9929A VDP using a Raspberry Pi
Pico
Author : classichasclass
Score : 46 points
Date : 2024-06-10 17:09 UTC (5 hours ago)
(HTM) web link (github.com)
(TXT) w3m dump (github.com)
| ComputerGuru wrote:
| VDP: video display controller/processor
| mturk wrote:
| The TI-99/4A community is really (and somewhat surprisingly)
| still very active. Among other things, the monthly stream from
| the CTIUG on YouTube ( https://www.youtube.com/@chicagotiug5404 )
| of their monthly meetings at the Evanston Library is actually
| quite fun, and the js99er.net (somewhat recently rewritten in
| Angular) emulator is just amazing.
| renewedrebecca wrote:
| It's really cool that the Pico has the horsepower to do this sort
| of thing instead of having to reach for a FPGA.
| jsheard wrote:
| The PIOs really are a superpower for this kind of thing.
| Interestingly the RP2040 documentation mentions that each PIO
| uses roughly the same silicon area as a dedicated peripheral
| for something like SPI or I2C, so now that the concept has been
| proven to work in practice it would be amazing if the successor
| chip ditched most of the single-purpose I/O peripherals and
| replaced them with a huge battery of PIO channels which can
| each be programmed to do SPI, I2C, or whatever else as needed.
| _Microft wrote:
| Here's a quote from Eben Upton (CEO of Raspberry Pi Trading,
| 2023):
|
| _"We know what people don't like about [RP]2040," Upton
| admitted at the event, "the [Arm Cortex-]M0+ [architecture],
| could have more RAM, could have more GPIO [General-Purpose
| Input /Output], and we know what people do like -- the PIO
| [Programmable Input/Output blocks]... and we have a chip
| team."_, [0][1]
|
| That doesn't sound too bad, hmm?
|
| [0] https://blog.adafruit.com/2023/12/04/raspberry-pi-hints-
| at-n...
|
| [1] https://www.hackster.io/news/eben-upton-hints-at-an-
| rp2040-s...
| jsheard wrote:
| Sounds good to me. The decision to go for two tiny cores
| rather than one beefier core with an FPU was strange, and
| it would be nice to have a PSRAM interface like the ESP32s
| do. They seem to want to have one chip SKU which does
| everything rather than a million variants, hence why they
| made the flash external on the RP2040, so if they can
| extend that to one chip which can be configured with
| variable flash size, memory size, and has tons of PIOs...
| jdswain wrote:
| The main constraint appears to be the number of available
| GPIO's. For 8-bit projects the bus can take a large number of
| pins, not leaving a lot for the other functions.
| jsheard wrote:
| Annoyingly the RP2040 has 30 GPIOs but the official Pico
| boards only break 26 of them out, which seems like an
| unforced error given the layout would have enough pins for
| all of them if it had less than 8 redundant GND pins. Those
| spare GPIOs are used to connect the WiFi coprocessor on the
| Pico W, but on the regular Pico one of them is just used for
| the onboard LED and the other 3 aren't connected to anything.
| fleventynine wrote:
| The redundant GND pins are necessary for signal integrity
| and low EMI when running at higher speeds; the high speed
| signals need a return current path with as little loop area
| as possible, so you want those signal pins close to GND on
| the connector.
| nsxwolf wrote:
| This is exciting because the current defacto standard for
| upgrading the graphics in a TI-99/4A is the F18A project, which
| is an FPGA based solution. It's really cool, but it's expensive
| and frequently unavailable.
|
| I am interested to see if this project evolves in the direction
| of F18A compatibility. It will need to support 80 column mode
| at a minimum before I switch.
| chasil wrote:
| The 9918 was used in much more hardware than the TI-99/4(a), and
| Yamaha produced a more capable version:
|
| "The TMS9918 and its variants were used in the ColecoVision,
| CreatiVision, Memotech MTX, MSX, NABU Personal Computer,
| SG-1000/SC-3000, Spectravideo SV-318, SV-328, Sord M5, Tatung
| Einstein, TI-99/4, Casio PV-2000, Coleco Adam, Hanimex Pencil II,
| and Tomy Tutor...
|
| "Texas Instruments' TMS9918A was succeeded by Yamaha's V9938,
| which added additional bitmap modes, more colorful sprites, a
| vertical full-screen scroll register, vertical and horizontal
| offset registers, a hardware blitter and a customizable palette."
|
| https://en.wikipedia.org/wiki/TMS9918
|
| MAME also implements the 9918 in software, as many of its
| emulation targets bundled it as a component (mostly video arcade
| games).
|
| https://www.reddit.com/r/MAME/comments/pw8285/is_it_possible...
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(page generated 2024-06-10 23:00 UTC)