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

Page 3/7
1 | 2 | | 4 | 5 | 6 | 7

By konamiman

Paragon (1116)

konamiman's picture

08-04-2021, 12:44

Quote:

but I know it is possible to have all the base functions of a Turbo R in a single IC

Have you considered the possibility of implementing a turbo Z80 instead of a R800, as the SX|2 does? This might simplify the design and you'd end up with a MSX2+ instead of a Turbo-R, but there isn't much software over there that uses the R800 or is exclusive for Turbo-R anyway.

By JEckert

Rookie (21)

JEckert's picture

08-04-2021, 15:59

I understand that, and that may ultimately be the plan for the MSX-C. I'm also open to compromise dropping V9990 support as well, if it weren't complicated by the fact that there are some games, particularly homebrew games, that require it. Getting a v9990 cartridge with it's own analog port would be inconvenient.

Alternatively, we could plan having a separate Z80 and save on cell space on the FPGA, because Zilog still produces the Z84C00, if you can trust their website. Getting a stand-alone Z80 seems feasible on paper.
https://zilog.com/index.php?option=com_product&Itemid=26&task=parts&familyId=20&productId=Z84C00&mpn=Z84C0006PEG&mpnid=5565&scrollmpn=1&rootpage=b3B0aW9uPWNvbV9wcm9kdWN0JnRhc2s9cHJvZHVjdCZidXNpbmVzc0xpbmU9MSZpZD0xMzkmcGFyZW50X2lkPTEzOSZJdGVtaWQ9NTk=

By konamiman

Paragon (1116)

konamiman's picture

08-04-2021, 16:41

The problem with using a real Z80 is that we lose the ability of having turbo clock speeds... or not? (I'm not an expert in hardware)

By AxelStone

Prophet (2892)

AxelStone's picture

08-04-2021, 16:47

konamiman wrote:
Quote:

but I know it is possible to have all the base functions of a Turbo R in a single IC

Have you considered the possibility of implementing a turbo Z80 instead of a R800, as the SX|2 does? This might simplify the design and you'd end up with a MSX2+ instead of a Turbo-R, but there isn't much software over there that uses the R800 or is exclusive for Turbo-R anyway.

The Zemmix Neo core implements Z80 with turbo speed and R800 instructions, so it's very compatible with Turbo R software if you install Turbo R BIOS in the machine. I agree with you, using a Turbo Z80 with R800 instructions added is a good choice.

The main problem, at least in Zemmix, it's the use of SDRAM. Because of this, Z80 clock can't go faster than 8Mhz or you get corrupted data, and to have the equivalent to R800 you need 28Mhz Z80.

By Metalion

Paragon (1343)

Metalion's picture

08-04-2021, 17:01

If you want to be ambitious, why not go all the way ?

I would include a "next-gen" MSX as well, like they did with the Spectrum "Next" :
- improved Z80 CPU, faster and with more instruction
- new VDP, with improved hardware capabilities

By JEckert

Rookie (21)

JEckert's picture

08-04-2021, 17:10

AxelStone wrote:
konamiman wrote:
Quote:

but I know it is possible to have all the base functions of a Turbo R in a single IC

Have you considered the possibility of implementing a turbo Z80 instead of a R800, as the SX|2 does? This might simplify the design and you'd end up with a MSX2+ instead of a Turbo-R, but there isn't much software over there that uses the R800 or is exclusive for Turbo-R anyway.

The Zemmix Neo core implements Z80 with turbo speed and R800 instructions, so it's very compatible with Turbo R software if you install Turbo R BIOS in the machine. I agree with you, using a Turbo Z80 with R800 instructions added is a good choice.

The main problem, at least in Zemmix, it's the use of SDRAM. Because of this, Z80 clock can't go faster than 8Mhz or you get corrupted data, and to have the equivalent to R800 you need 28Mhz Z80.

Well, if SDRAM is unavoidable, the 8MHz model of the Z84C will have to do if you want double the base clock of the Z80 that ran on MSX machines.

Z84C0008PEG

Features
Package - DIP
I/O - N/S
WDT - No
Timers - No
Pin Count - 40
Speed (MHz) - 8
Operating Voltage - 5.0V
External Memory - 64KB
Core/CPU Used - Z80
Communications Controller - CPU

That's assuming we end up with a separate Z80, but I'm hoping that doesn't happen, everything CPU/VDP related gets put into one package.

By konamiman

Paragon (1116)

konamiman's picture

08-04-2021, 17:12

Hi JEckert, you have a pull request in your repository to enhance the markdown formatting of the abstract (without any content changes).

By konamiman

Paragon (1116)

konamiman's picture

08-04-2021, 17:16

Metalion wrote:

If you want to be ambitious, why not go all the way ?

I would include a "next-gen" MSX as well, like they did with the Spectrum "Next" :
- improved Z80 CPU, faster and with more instruction
- new VDP, with improved hardware capabilities

I think that the goal of the project is cost-effectiveness more than ambition Smile

Also, as I see it:

- Faster CPU: big yes, but more instructions? I don't think many software would be made using these (in the same way as I don't see that much R800-capable software).
- New VDP: we have just started to scratch the surface of what the V9990 can offer, I don't think we need yet another new VDP for now.

Sorry for being pessimistic Tongue

By JEckert

Rookie (21)

JEckert's picture

08-04-2021, 17:19

konamiman wrote:

Hi JEckert, you have a pull request in your repository to enhance the markdown formatting of the abstract (without any content changes).

Looks good. Approved and merged.

By JEckert

Rookie (21)

JEckert's picture

08-04-2021, 17:23

konamiman wrote:
Metalion wrote:

If you want to be ambitious, why not go all the way ?

I would include a "next-gen" MSX as well, like they did with the Spectrum "Next" :
- improved Z80 CPU, faster and with more instruction
- new VDP, with improved hardware capabilities

I think that the goal of the project is cost-effectiveness more than ambition Smile

Also, as I see it:

- Faster CPU: big yes, but more instructions? I don't think many software would be made using these (in the same way as I don't see that much R800-capable software).
- New VDP: we have just started to scratch the surface of what the V9990 can offer, I don't think we need yet another new VDP for now.

Sorry for being pessimistic Tongue

Spot on with what I'm trying to make here. MSX is currently NOT a system to get into on a budget (ignoring emulation)
MSX-C intends to address that.

Page 3/7
1 | 2 | | 4 | 5 | 6 | 7