Z280 booting MSX, progress!

Door lintweaker

Master (227)

afbeelding van lintweaker

28-03-2020, 13:14

With all the inisde the house time I decided to revisit my Z280 board to see if I could finally get some real use out of it. After some fiddling with the Z280 configuration registers I can finally use it to boot into MSX1, MSX2 and MSX2+ on my DIY MSX (Z8TY)!

Basically all the advanced Z280 features like caching have to be disabled to make it work for MSX.
I/O operations like accessing the VDP have to be really slowed down otherwise there is corruption or nothing on the screen at all. Using VDPWAIT helps but is not always enough.

Now to see if I make it work with higher frequency clocks, I probably have to add extra hw to slow down I/O port access. Using the internal configurable I/O waits (up to 3) is not enough (at least for the VDP).

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Van erpirao

Paragon (1041)

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28-03-2020, 14:11

What VDP are you working on?
The 9958 and 9990 have their wait signals, it may be interesting to keep them in mind.

Van lintweaker

Master (227)

afbeelding van lintweaker

28-03-2020, 14:33

erpirao wrote:

What VDP are you working on?
The 9958 and 9990 have their wait signals, it may be interesting to keep them in mind.

On the V9958 with VDPWAIT enabled (as mentioned). I have a V9990 but still have not programmed it myself.

Van jltursan

Prophet (2273)

afbeelding van jltursan

28-03-2020, 15:04

How much delay seems to be needed between accesses?, I think that the V9958 is a retty fast VDP (faster than V9938?, not sure about that), you must be outputting data at a very fast rate.

Van erpirao

Paragon (1041)

afbeelding van erpirao

28-03-2020, 20:41

lintweaker wrote:
erpirao wrote:

What VDP are you working on?
The 9958 and 9990 have their wait signals, it may be interesting to keep them in mind.

On the V9958 with VDPWAIT enabled (as mentioned). I have a V9990 but still have not programmed it myself.

Sorry, it is true that you had mentioned it but I had read too fast.
have you done any performance tests with z280 at 3.57mhz?
There are games that if you can get them to start (ys III, or D.I.O.S.) can be a good performance test.
we are waiting for more news of your progress.