The Strange case of a Victor HC-95(a) 512KB!

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Por sdsnatcher73

Prophet (3526)

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06-06-2022, 06:06

retrocanada76 wrote:

unfortunately Nextor fails with kernel error 6 when switching Z180.

Sofarun also does not run it exits instantly on z180. Does it really pay using undocumented instructions on these ?

I don’t know if the undocumented instructions are the cause or not using the BIOS. The problem with the Z180 from what I’ve read (and remembered) is mostly timing. The (altered) BIOS takes care of any delays needed but Nextor and SofaRun probably don’t. Does MSX-DOS2 work (e.g. from an MMCSD cart)?

Por sdsnatcher73

Prophet (3526)

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06-06-2022, 06:42

gdx wrote:

I remember seeing an excerpt from the documentation for the HC-90/95. It said that the Z80/Z180 switching should be done when the computer is off only. Then several people say that most games that do direct accesses do not work in Z180 mode. Panasonic did much better with the Turbo R.

Well, the turbo R was obviously designed by ASCII. I think the advantage of having an S1990 to ’temper’ the faster CPU instead of relying on the BIOS is the main difference between the 2 designs.

Por lintweaker

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06-06-2022, 08:06

If I remeber correctly, Nextor uses some undocumented instructions like IXh IYl etc. The Z180 does not support these.
Thats way Nextor does not work.
Furthermore, the Z180 uses 64 IO addresses for internal peripherals, this does not help either wrt use with MSX. By default they occupy IO ports 0-63. These can be remapped but will then surely clash with MSX standard IO ports.

Por sdsnatcher73

Prophet (3526)

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06-06-2022, 08:40

lintweaker wrote:

If I remeber correctly, Nextor uses some undocumented instructions like IXh IYl etc. The Z180 does not support these.
Thats way Nextor does not work.

That is too bad, software like Nextor should try to be compatible imho. Maybe a patch could be made?

lintweaker wrote:

Furthermore, the Z180 uses 64 IO addresses for internal peripherals, this does not help either wrt use with MSX. By default they occupy IO ports 0-63. These can be remapped but will then surely clash with MSX standard IO ports.

Wouldn’t the modified BIOS in the HC-90/95 already take care of this? Otherwise it could not be “MSX compatible”. I guess it could be tested by using a Music Module in turbo mode, right?

Por gdx

Enlighted (5696)

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06-06-2022, 08:44

I think Victor developed the Z180 mode as an extra for professional use. The main goal was not compatibility. Otherwise, Victor would have chosen another CPU.

Por retrocanada76

Hero (538)

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07-06-2022, 01:48

Sunrise BIOS on a Maxiol Card boots MSX-DOS 2.44 nicely. The z180 runs CP/M application from msx-dos pretty fast. I need to compare to the turboR making a racing video lol...

As a correction the hc-95 does not have a z180 but an HD64180, which was a base design for the z180
The xx180 has a trap interrupt for invalid opcode. Maybe there is hope to create an emulation layer for undocumented but such thing would be very hard to implement we don't have an openMSX capable of running the hd64180 code yet.

Por gdx

Enlighted (5696)

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07-06-2022, 02:57

The HD64180 is a z180 from Hitachi. Compared to Z80, it has a different operation mode control register function (bus switching) and instructions with IXL/IXH, IYL/IYH are missing, so some software changes are required.

Its speed is also a problem for programs that make I/O direct accesses (as with almost other turbo modes).

Por retrocanada76

Hero (538)

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07-06-2022, 03:23

Hey, can I change it to a Z180 ? It's socketed I could give a try

Por gdx

Enlighted (5696)

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07-06-2022, 09:31

I think is not possible because pins /DR, /ME, /IOE and /REF replace the pins /M1, /MREQ, /IORQ and /RFSH. HD64180 is a z180 whose hardware is closer to z80, but I was talking about software compatibility.

Por lintweaker

Champion (437)

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07-06-2022, 11:48

gdx wrote:

I think is not possible because pins /DR, /ME, /IOE and /REF replace the pins /M1, /MREQ, /IORQ and /RFSH. HD64180 is a z180 whose hardware is closer to z80, but I was talking about software compatibility.

Hmm. which version of the Z180 are you talking about? The Zilog Z8S180 just has all the Z80 pins like /M1, /RFSH etc and of course others for the built in peripherals.

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