V9990 FPGA recreation.

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By lintweaker

Champion (415)

lintweaker's picture

09-02-2021, 20:17

I would not mind an (initially) basic V9990 implementation. Hopefully HRA! will really start with it.

By AxelStone

Prophet (3046)

AxelStone's picture

09-02-2021, 22:04

PingPong wrote:

would be nice to have instead a v9990 implementation. however i think it will not be a reality.
Maybe a v9958 replaceable core with improved functions like a really fast blitter, decent sprites, like F18 for the TMS?

We already have a "fast 9958" implemented in OCM / Zemmix. It unlocks the comunication speed between VDP and VRAM (that in OCM / Zemmix is much faster than original VRAM used in MSXs) and it goes reaaaally fast. Sometimes I've thought that very good games could be done using this speed, you can perform COPY commands so fast that you could do smooth games using pure software sprites (no color limit).

Obviously the main disadvantage is compatibility: only FPGAs based MSX would be compatible.

By PingPong

Prophet (3758)

PingPong's picture

09-02-2021, 22:39

i know but is is OCM - Tied. i mean something like a F18.
open your msx, desolder or pull out your v99x8 from a socket, insert the new socket adapter with the OCM V99x8 and go!

By st1mpy

Paladin (825)

st1mpy's picture

09-02-2021, 22:49

If a fpga 9958 is that fast because of the ram used for vram, having a fpga 9958 in a cartridge and plugged to a real msx will be just as good?!

By PingPong

Prophet (3758)

PingPong's picture

10-02-2021, 00:42

st1mpy wrote:

If a fpga 9958 is that fast because of the ram used for vram, having a fpga 9958 in a cartridge and plugged to a real msx will be just as good?!

not so good as a hw replacement. because of fixed 0x98 ... 0x9a vdp port addresses.
Would be the same as the msx2 upgrade cartridge for msx1.
a socket replacement would be better. replace the old vdp with a socket and install somewhere the new vdp into the machine without using any free slot

By AxelStone

Prophet (3046)

AxelStone's picture

10-02-2021, 10:21

I agree, if you are going to plug a external cartridge we already have 9990 that has more features than turbo 9958. However as I said, the turbo 9958 VDP (that really is the normal 9958 with very fast VRAM) has incredible COPY capabilities (x5 compared to normal speed) and would result in very impressive software.

Perhaps in the future with a solid FPGA base we could see games designed for it Smile

By sdsnatcher73

Prophet (2229)

sdsnatcher73's picture

10-02-2021, 10:32

Just dreaming here but what if we could actually make V9978 in FPGA and make it pin compatible with V9938/V9958. Have it as a drop in replacement of existing VDP (maybe with a jumper to select V9938/58 pinout). The module could have it’s own and faster VRAM.

By gdx

Enlighted (4693)

gdx's picture

10-02-2021, 11:09

Making a V9978 pin compatible with the V9958+V9990 is not possible because it involves using the same I/O ports to access the V9990.

Instead of bothering for years to reproduce a little documented CPU that is little used, it might be better to make a cartridge with a video input (PAL / NTSC) to be able to display both images on the same screen (HDMI) by transparency. This could have a new GPU. The main thing is that it is fast, easy to use and cheap.

This new GPU would allow us to make a nice UI for Nextor without interfering with the software compatibility.

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