Any interest in a DIY MSX hardware group

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Por megatron

Resident (41)

Imagen del megatron

27-07-2015, 12:53

My idea was rather simpler than most...keeping things very basic and simple, thus hopefully reducing costs and complexity. So anyone could get a bare PCB and make their own MSX 2 Clone at a homebrew hobby price !

Done some basic costings for a Crude inexpensive MSX 2 homebrew system. These are prices on stuff I've already bought so I know the IC prices are pretty accurate. Should be able to make a DIY/Homebrew MSX 2 for about $80 to $100.. Though that's the easy bit design,building, testing and making it are the hard part !!

Z84C0008PEC $2.0 each or less
128K SRAM DIP32 (TC551001,HM628128 etc) <$1.0 each
128K or 64K EPROM (Cheap) DIP28/32 <$1.0 each
EPM7032SLC44 CPLD PLCC44 (32 I/O lines) $2.0 each
EPM7128SLC84 CPLD PLCC84 (64 I/O lines) $2.0 each
V9938 Video with DRAMs and PAL/NTSC encoder about $15.0
YMZ284 DIP16 package $2.50 each
SN76489 $0.50 each
8255 <$2.0 each
ATmega88 about $1.0 each
Connectors/sockets about $15.0 to $20.0

Cartridge sockets etc still to be sources/priced

Hopefully all in $80 gto $100 based on an inexpensive PCB. Avoiding ** Complex multilayer PCBs which can be expensive!

I'm afraid FPGAs and stuff are above my Brain Capacity, simple Boolean equations and CPLDs will have to do for me !

Por darkschneider666

Supporter (8)

Imagen del darkschneider666

27-07-2015, 15:24

My two cents
I agree with Grauw: "FPGA-based MSX with discrete V9958 and YM2413. The FPGA will fulfill the role of the MSX-ENGINE including Z80, PSG, etc., while having the VDP and FM chip discrete for perfect, accurate and reliable video and sound."

I don't think the R800 and S1990 need to be fully implemented. All of the R800 have more than Z80 and that is used in the TR can be implemented into T80 core and with some more modifications can "upgrade" the T80 core to be fully compatible with Z80 and R800, of course with the same register to change the "cpu" only change the "cpu mode", this was used in other processors.
Anyway, this way can be created like a "new" version of the MSX-Engine, as ASCII always was doing with S3527, T7937, S1985, T9769, etc.

People that don't like FPGA, just know that if want implement in silicon, the cost of this is more than 300k dollars (this with lucky), so nobody will pay more than $500 for one IC, so FPGA is pretty good solution with a maximum cost of $50.
For the 8255, PSG, Z80 FPGA implementations have pretty good compatibility.

The big question is the keyboard, need to have the "ps2 to ppi" adaptation because of the softwares that read directly the keyboard.

One small question is the BIOS, with some work i belive that C-Bios can work fine, or a new BIOS? i'm not really sure about it. Smile

Por tvalenca

Paladin (747)

Imagen del tvalenca

27-07-2015, 20:14

darkschneider666 wrote:

The big question is the keyboard, need to have the "ps2 to ppi" adaptation because of the softwares that read directly the keyboard.

Isn't better to stick to the standard and ignore this "PS2 to PPI" (or even USB to PPI) adaptation? Softwares that don't stick to the coding guidelines should be patched, like we did with the ones that "doesn't like" having ROM or RAM on an expanded slot.
When you learn that the very first IBM PC (before the PC-XT) used one i8255 (yes, "our" PPI) to read the keyboard matrix, and later versions used one i8042 (or supersets of it), and both plataforms have a BIOS CALL to read the keyboard, you notice it's much logical to do that instead of losing the temper on more hardware protocol translations, putting a modern micro-controller with 50 times more power than the main processor just to read a shitty keyboard. (and have ghosting issues multiplied by 50 thousands)
So, if someone would ever ask me what I think, I'd say: Either you do it right from the beginning and use PS2 and/or USB-HID protocols natively, (better than design a time critical state machine to update a virtual keyboard matrix) or you get one real MSX keyboard and use a PPI to read it (either with a REAL i8255 or a CPLD/FPGA implementation, that's your call)

darkschneider666 wrote:

One small question is the BIOS, with some work i belive that C-Bios can work fine, or a new BIOS? i'm not really sure about it. Smile

The major drawbacks using C-BIOS are the lack of DISK support and BASIC. But I think it's desirable to use C-BIOS, since we're not allowed to use copyrighted software (BIOS) on this new machine. (ok, that happens also with Games, DOS and other programs, but we shouldn't....)

Por Manuel

Ascended (18390)

Imagen del Manuel

27-07-2015, 21:07

Of course it would be even better if people would help the C-BIOS project to add DISK and BASIC support!

Por Pac

Scribe (6539)

Imagen del Pac

28-07-2015, 10:58

megatron wrote:

Done some basic costings for a Crude inexpensive MSX 2 homebrew system. These are prices on stuff I've already bought so I know the IC prices are pretty accurate. Should be able to make a DIY/Homebrew MSX 2 for about $80 to $100.. Though that's the easy bit design,building, testing and making it are the hard part !!

Z84C0008PEC $2.0 each or less
128K SRAM DIP32 (TC551001,HM628128 etc) <$1.0 each
128K or 64K EPROM (Cheap) DIP28/32 <$1.0 each
EPM7032SLC44 CPLD PLCC44 (32 I/O lines) $2.0 each
EPM7128SLC84 CPLD PLCC84 (64 I/O lines) $2.0 each
V9938 Video with DRAMs and PAL/NTSC encoder about $15.0
YMZ284 DIP16 package $2.50 each
SN76489 $0.50 each
8255 <$2.0 each
ATmega88 about $1.0 each
Connectors/sockets about $15.0 to $20.0
Cartridge sockets etc still to be sources/priced

Your concept-proposal about a low cost MSX2 is good mainly if we want to replace our old hard that sooner or later will fail but I think that most of us would like to boost that supposed MSX a bit. In my opinion we shouldn't bet for a MSX with some restrictions from the beginning so a more powerful Z80, V9958 and YM2413 is a must. We should to avoid repeating past mistakes. Smile

Por Alexey

Guardian (3285)

Imagen del Alexey

28-07-2015, 14:18

If I think about a new DIY MSX, the following wishlist comes to mind:

- ATX form factor board with ATX power supply connectors
- z80 with selectable modes (normal/turbo)
- 192kb VRAM (or even more if possible)
- 1024kb RAM
- 9958 vdp
- default sound + PSG
- switcheable stereo fmpac (full version)
- switcheable f4 register
- 3 cartridge slots
- ps2/usb connectors for modern keyboard/mouse
- slider to control CPU speed (like in Sony F1-XV)
- autoshoot slider and switch like in MSX2+
- 2 joystick ports (and maybe USB port for joysticks?)
- floppy disk controller for PC floppy drives
- CF or SD card slots (IDE controller too if CF is implemented)
- RGB+HV sync and Composite + S-Video outputs
- VGA output (would be best, but may be expensive ulness implemented in FPGA)
- serial port (does someone need this?)

Maybe a crazy idea, but a flashable ROM BIOS would be great. Also other ROMs should be either socketed or flashable.

Alexey

Por darkschneider666

Supporter (8)

Imagen del darkschneider666

28-07-2015, 15:01

tvalenca the problem for use the ps2 and/or USB-HID protocols natively it's exactly the many softwares don't use the BIOS call and access the keyboard directly, so if will be implemented the protocols natively theses softwares will need to be patched, with this translation of ps2 protocol to PPI interface will resolve this problem (btw OCM does that) and no patched is need.

i'm not saying put that in a moder microcontroller, put that in the FPGA "MSX-ENGINE". Btw is what you said after, but still is a "adaptor" or a "Protocol translator" or "glue logic" or anything you want to call.

The problem of the "real MSX Keyboard" is you need to manufacture all keyboard, and as you said even a modern PC go to PS2 Protocol. Tongue

Por Capitan_Goto

Master (168)

Imagen del Capitan_Goto

28-07-2015, 15:21

I like very much the idea of Alexey ...

Por syn

Prophet (2086)

Imagen del syn

28-07-2015, 15:40

I agree with you PAC. I'd say minimum spec for any new project should be at least msx2+ with v9958 and opll (and obviously psg). Parts are not hard to get, and FPGA also exists for these parts.

Ideally, I think specs should be turbo R with 4MB RAM and opl4+v9990 as well. Why? Imho this is at the moment the highest possible spec for MSX that is according to standard with its spiritual successors added.

Some more added fun would be to have the OPL4 contain 4MB sram, and without the standard rom sounds (maybe have some bios option making it able to enable them for existing software). I mention this because while the OPL4 can have 512 instruments, the build in rom kit uses 384 of those, so you can have at most 128 own instruments (64 in MBwave/FM). This sounds a lot but if you factor in sound effects as well this start to become limiting.
Also a switch to choose either have v9990 and v9958 through 1 monitor output or send v9990 signal to a second output would be useful imho. Some people dont like 2 monitor setup, while some think its useful. Sometime space is a problem.

Ofcourse the standard stuff should be included as well, like SCC and flashrom, SD card reader. Connectors for USB keyboard/controllers would be cool. And VGA output is important imho.

Besides that, I'd love to see MSX audio with 256kb sram on it as well. It is a personal favorite, and I hope this one will become popular again in the msx scene. Add a switch for mono (psg&fmpac+ msx audio on both channels) and stereo (psg+fmpac one channel, msx audio other). Or even better some stereo "spread" dial so you can set your own stereo width) (basically 2x balance control in 1)

Ethernet, Midi interface, and may Nowind (This one is so convenient while developing imho) would be great too Big smile

Por Grauw

Ascended (10306)

Imagen del Grauw

28-07-2015, 17:29

Alexey wrote:

- 1024kb RAM

Why not 4096K? I have VGM songs where 1 MB is not enough to load them into memory. Maybe I’m wrong, but in the age where 16 GB RAM is becoming the standard for desktop computers, surely the cost difference between 1 and 4 MB will be negligible?

Alexey wrote:

- serial port (does someone need this?)

I thought about adding MIDI to my ideal system, but it would just add to the cost while a lot of people won’t use it. Same story for RS232.

I agree with RetroTechie’s comment about not including everything and the kitchen sink. MSX is an expandable system at heart, we already have cartridges for a lot of things, so for me it would be most important to have a good spec for the core parts that are not expandable (CPU, VDP, video & joystick/mouse/keyboard interface).

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