Search found 760 matches

by siggi
Fri Nov 24, 2017 11:22 am
Forum: Hardware
Topic: Help with Homemade ZX80-81- HIRES problem
Replies: 37
Views: 476

Re: Help with Homemade ZX80-81- HIRES problem

Hi Luciano one more hint: during REFRESH, the MREQ-signal is shorter than during normal READ/WRITE. Maybe that is the reason, why they used GND instead of MREQ (during refresh) to enable ROM (ROMCS is then active as long as REFRESH is low): they could use slow roms. So if you want also to use slow (...
by siggi
Fri Nov 24, 2017 8:21 am
Forum: Emulators
Topic: New release of EightyOne available
Replies: 123
Views: 7336

Re: New release of EightyOne available

Tried: does not crash on start :mrgreen: But it wants to have a "DirectDraw.dll"(probably "DirectX 9.0c (June 2006)"). The links to a WIN98 DLL version I already found point to "file not found" or "timeout". :roll: Its is much easier to run an old Zeddy than to run a much newer (old) PC :roll: Siggi
by siggi
Thu Nov 23, 2017 9:02 pm
Forum: Emulators
Topic: New release of EightyOne available
Replies: 123
Views: 7336

Re: New release of EightyOne available

Is there a version (maybe very old), which runs with WIN98SE? I have revived my old Toshiba Libretto 100CT (which has been used for several years as router for my ZX81 web-server) and would like to use it with EO. I am sure, it is fast enough (166 MHz) to emulate a 3,25 MHz Zeddy (maybe not for a 20...
by siggi
Thu Nov 23, 2017 7:44 pm
Forum: Hardware
Topic: Help with Homemade ZX80-81- HIRES problem
Replies: 37
Views: 476

Re: Help with Homemade ZX80-81- HIRES problem

Hi Siggi. Yes, probably during low refresh period the ROM add some data on data bus. I am planning to add some additional logic .. to disable the ROM or add some delay, during refresh period. (just to understand better the problem) Some idea about which signals needed to disable ROM in the right ti...
by siggi
Thu Nov 23, 2017 9:46 am
Forum: Hardware
Topic: Help with Homemade ZX80-81- HIRES problem
Replies: 37
Views: 476

Re: Help with Homemade ZX80-81- HIRES problem

Hi Luciano I don't understand, that ROM (or something similar) affects the behaviour of RAM. Maybe there is a collision between ROM and RAM due to an error in address decoding the RAM or ROM area? Then not the speed of the ROM, but the strenght of its databus output drivers would more or less affect...
by siggi
Wed Nov 22, 2017 6:02 pm
Forum: Hardware
Topic: Help with Homemade ZX80-81- HIRES problem
Replies: 37
Views: 476

Re: Help with Homemade ZX80-81- HIRES problem

Hi Luciano the picture above is OK to generate /RAMCE: http://www.sinclairzxworld.com/download/file.php?id=4975 And to generate /OE you should use an AND gate: /RAMOE = /RS AND /RFSH (any of /RD or /RFSH LOW shall enable ram output and give a LOW at /RAMOE) About capacitors: you should have approx. ...
by siggi
Wed Nov 22, 2017 2:48 pm
Forum: Hardware
Topic: Help with Homemade ZX80-81- HIRES problem
Replies: 37
Views: 476

Re: Help with Homemade ZX80-81- HIRES problem

Hi Luciano you should use this logic as given above: This is from the ZXpand RAM select logic. RAM = true when RAM is required. assign IFRAMOE = !nRD | !nREFSH; assign IFRAMCE = (!nMREQ | !nREFSH) & RAM Could you show us a picture of your ZX81? Maybe there are other problems? Not enough deblocking c...
by siggi
Tue Nov 21, 2017 1:46 pm
Forum: Welcome Area
Topic: Pictures of Our Babies.
Replies: 14
Views: 349

Re: Pictures of Our Babies.

And here you can see, what Joachim uses his ZX81 for:

https://www.youtube.com/watch?v=-WudgMDa5kc

https://www.youtube.com/watch?v=2hIty9hYKfQ

:mrgreen:

Siggi
by siggi
Fri Nov 17, 2017 5:58 pm
Forum: Welcome Area
Topic: Pictures of Our Babies.
Replies: 14
Views: 349

Re: Pictures of Our Babies.

Here are some pictures of German babies ;)

http://forum.tlienhard.com/phpBB3/viewt ... ?f=2&t=300

Siggi
by siggi
Tue Nov 14, 2017 3:42 pm
Forum: Hardware
Topic: ZX81 cooling fan
Replies: 56
Views: 848

Re: ZX81 cooling fan

Actually the third pin should be used to control the speed of it. But I have no idea how... Maybe use a pic or arduino to set the speed, in relation to the internal heat. I leave it up to you which point you will measure. The downside of this again is that the pic has more processing power than the...