MSX Hardware Emulator Experience

Por jburrell7

Supporter (4)

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10-03-2017, 16:04

I am not sure if this is the correct forum for this question (it may belong in the hardware area), but does anyone have any experience with the Terasic DE1 emulator that is at http://caro.su/msx/ocm_de1.htm?

I have been playing with it and would like to know how well it emulates a MSX computer. I am very new to the MSX scene - living in the US it was never very popular here - but I am intrigued with its capabilities. I am presently waiting for PCBs to implement the joy stick and mouse interface and, if it is an accurate emulator, I would like to add a properly buffered cartridge port to the the next spin of the PCB. The respin would be a four layer PCB with proper power planes, but I would like to know that it is worth going to the higher expense.

I would eventually like to start programming for the MSX and I am not too interested in software emulation (I am a hardware engineer so software is a necessary evil ;) ), so a good hardware emulator would be welcome - especially FPGA based since I can hack the hardware to take it to a higher level.

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Por PingPong

Prophet (3793)

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10-03-2017, 17:19

i do not know if can help but there is a FPGA emulation of the entire computer. It's called OCM (on chip msx).
basically msx is based on commercial hw no custom chips except the video chip that is a chip developed by yamaha and backward compatible with the old TMS 9918 VDP. Sound wise there is a general instrument AY-3-8910, the cpu is a z80 @ 3.5Mhz, there is also a intel PPI. RAM chips are the usual 300ns DRAM ...

Por Grauw

Ascended (10174)

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10-03-2017, 20:22

The OCM emulation is not perfect but good in general. It runs most software fine. For development, maybe better to use openMSX because it’s better at the details, and of course it’s always best to test on original hardware.

As an example of such details, one OCM bug I ran into in the past was the behaviour of line interrupts in the vertical blank period, they’re supposed to continue past line 212 but the OCM doesn’t emulate this properly currently. Another is that the SCC period counter doesn’t reset when writing a new frequency; although this arguably makes it sound better, if you only test on that during development it could give a bad surprise when you finally try it on a real SCC.

Btw, I have a Zemmix Neo myself, used to have an 1chipMSX before that. Nice hardware, I like it.

Por jburrell7

Supporter (4)

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10-03-2017, 21:54

I have extensive VHDL experience and made a TS2068 clone for my DE1 board that is pretty close to the original hardware. It would be fairly easy for me to make any changes to the FPGA code to fix the known bugs. I also plan to add ethernet or wifi to my prototype as well as a battery backed real time clock.

Por Pac

Scribe (6478)

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11-03-2017, 20:19

jburrell7 wrote:

I would eventually like to start programming for the MSX and I am not too interested in software emulation (I am a hardware engineer so software is a necessary evil Wink ), so a good hardware emulator would be welcome - especially FPGA based since I can hack the hardware to take it to a higher level.

I also prefer a hardware based machine instead a software one, so any contribution is welcome. If helps check the wiki about OCM.

Por jburrell7

Supporter (4)

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11-03-2017, 22:51

How important are the cartridge slots for a hardware emulator such as the OCM?
Would anyone be interested in an FPGA based emulator?
If so, what would be a reasonable price point for one?

For instance, a Terasic DE0 development board runs about 120USD and provides 4MB RAM, 128K VRAM, VGA display output, one serial port, SD card storage, PC keyboard and mouse. A separate PCB with two slot connectors, two joystick connectors, battery backed RTC, a 9 pin serial port, an optional ethernet, and a power supply to run the MSX slots would run an additional 80USD (approximately). That is not a small amount, but still not outrageous, either.

This is only one example. There are trade-offs to be made in cost, capability and the age of the FPGA. Older FPGAs are less capable and will get more expensive as the manufacturer phases them out in favor of newer devices.

Comments?

Por jburrell7

Supporter (4)

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25-03-2017, 03:19

I have received the prototype PCBs to add a RTC and a Microchip ENC28J60 Ethernet module to my DE1 OCm board. I am aware that there are other Ethernet boards for MSX that are based on this chip and I would like to make my hardware compatible with them. Does anyone know how I can get the information to do this?