MSX-C — A new, low-cost MSX Turbo R computer!

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By konamiman

Paragon (1117)

konamiman's picture

15-04-2021, 09:31

sd_snatcher wrote:

If you do, pretty-pretty-please remember to ask him for the official sources of all other MSX ROMs too, like the mainBIOS, subROM, optROM, MSX-Audio, MSX-Music, MSX-MIDI, MSX-RS232, MSX-Modem, MSX-JE, MSXView etc

These might not even exist at this point. He explicitly told me that the sources of MSX-DOS 1 were lost.

By AxelStone

Prophet (2919)

AxelStone's picture

15-04-2021, 11:54

JEckert wrote:

Ultimately, as far as components go, the less chips, the better. We absolutely need Z80, V9958 PSG and MSX-MUSIC to be in one FPGA to make it a viable machine, but I also want WiFi and Ethernet (both to supplant network cartridges and for online updates and downloading games), and internal flash storage for those games (don't see any publisher, whether it is Konami or an indie developer, liking games stored into SD without extra antipiracy steps). If we can get an FPGA to work with these extras, I think we can discuss squeezing more functionality if we have the spare cells for it. At the very least, the test model should act like a bona fide MSX2+ with HDMI, WiFi and secondary storage. That would be a sound foundation.

Piracy is not a problem related to SD, is a problem related to behaviour of some persons. Removing SD slots will reduce a lot the usability and capabilities of the model. As @konamiman suggest, a lot of actions can be performed using the SD, like for example update firmware, store your own programs and, why not, make backup of your games.

By JEckert

Rookie (21)

JEckert's picture

15-04-2021, 20:13

I think we'll need to include a CPLD to interface with the bios, sd, and network interfaces.

I think we should decide on either SD or USB for supplementary usage alongside flash. Personally, I would choose SD over USB, but the decision should be based on how much is saved in money and FPGA space. I am open to ditching flash storage, but secondary storage is required for saving games and settings, and would need to stay inserted while the machine is powered. I rather have flash storage because it's easier. Alternatively, I can go with flash only, plus a usb micro port for data transfer. Let me know what you think.

Finally, voltage shift buffers between the 5v MSX bus and 3.3v bus would ensure reducing noise and power consumption better than simple resistor buffers.

By konamiman

Paragon (1117)

konamiman's picture

15-04-2021, 22:21

Ideally I would implement:

- SD slot for settings, custom firmware, and storage (although I'm not sure how we could make this visible for the FPGA part and for the MSX simultaneously without causing conflicts)
- USB port for expansion. That would be exclusively for the MSX, the FPGA (or CPLD) part would just make it visible to the MSX via Z80 port or similar mechanism.

By Manuel

Ascended (17752)

Manuel's picture

15-04-2021, 23:43

Wouldn't flashROM be useful for the (upgradable) ROM content? And perhaps also to run/develop software with particular mapper types.

By konamiman

Paragon (1117)

konamiman's picture

16-04-2021, 09:24

Manuel wrote:

Wouldn't flashROM be useful for the (upgradable) ROM content? And perhaps also to run/develop software with particular mapper types.

As an alternative to FlashROM perhaps RAM can be used for this purpose: the contents of the slot would be loaded from SD on boot, but then a mechanism is needed to prevent the slot contents to be writable afterwards. That's how MegaSCSI works: it stores its BIOS in battery-powered SRAM which is normally read-only, but becomes writable when you set the MSB of the "ROM" page number when mapping it.

Additionally, regardless of whether flash or RAM is used, a "factory reset" mechanism is needed to boot with default ROMs in case no SD card is present or a faulty ROM is flashed/loaded.

By erpirao

Paragon (1169)

erpirao's picture

16-04-2021, 14:49

Good afternoon, I am reading the thread, and it is still not clear to me what the objective of the project is:
1.- design a DIY turboR compatible board (or a whole system).
2.- design or build a board (or system) to be officially sold.
3.- design or build a new but compatible MSX
but I see that the planning of the system is not finished, in my opinion it has to be done from "less to more", that is, as the MSX specification was made.
we set a specification and on a solid base we have already evolved.
an example might be the late Leonardo Padial's specification: eMSX2 ++, with some improvements.
as a "personal" specification, the base should be:
z80 @ 20mhz with turbo modes (in the style of FPGA implementations, like the OCM).
Z280 @ 12MHZ (25 internal)
2MB system ram (mapped for z80 and linear for z280)
v9958 (128KB) and v9990 (512KB)
cpld with psg, ppi ..
ym2413 msx music
y8950 msx audio (with 256KB adpcm).
2Mbyte flashrom for bios and drivers.
at least one compatible MSX-50pin slot
at least one "new MSX" slot for new developments.
surely my specifications slightly exceed the $ 100 target cost, but at least in my case I am more than willing to pay them.

By JEckert

Rookie (21)

JEckert's picture

20-04-2021, 20:03

Feedback is looking good. I'm getting close to updating the abstract, but there are still several points of contention. Are these features viable:
*SoC via programmable logic ICs
-Z80 w/Turbo
-V9958 graphics, 128k VRAM
-PSG, MSX-Music, and SCC built-in
*Flash + SD storage (games, saves, settings, updates to bios/firmware/programmable logic)
*2 Cartridge Slots
*Integrated full-travel dome-switch keyboard
*2 game pads included
*HDMI audio/video output

My gut says it is, but my question to devs experienced in hardware, software, and logic programming, who are interested in this project concerns mass production and future expansion. With hopes to create these machines and sell them at US$180 a piece, can we make a machine with these base features and leave room for expansion? I invite your feedback, as this will shape the final draft of the abstract and serve a foundation for a subsequent, more concrete scope.

By hamlet

Scribe (3530)

hamlet's picture

20-04-2021, 21:17

What makes you calculating 180 US$?

By st1mpy

Paladin (737)

st1mpy's picture

20-04-2021, 23:11

I don't know the exact cost of hdmi license but I think it is unaffordable for this kind of project.

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