Welcome, Guest. Please login or register.


Author Topic: 6Mhz and more... (Read 29467 times)

Offline IstvanV

  • EP addict
  • *
  • Posts: 4806
  • OS:
  • Linux Linux
  • Browser:
  • Firefox 35.0 Firefox 35.0
    • View Profile
Re: 6Mhz and more...
« Reply #30 on: 2015.April.10. 14:56:37 »
As far as I know, for other solution (like 7.12MHz, derived from ~14Mhz pixel clock of Nick, I suppose) do not have this problem and Dave can be left in its "usual" state (as it would be for 4Mhz machine) but still having the right timings for sound, etc. Is it true?

No, it also overclocks both the DAVE chip and the Z80, which always runs at half the clock frequency of DAVE. In this case, even with the 12 MHz bit set, the pitch of the sound generators is too high by about 3 semitones, and the 1 Hz/50 Hz (not video)/1 kHz interrupts are generated at higher frequency as well.

Offline lgb

  • EP addict
  • *
  • Posts: 3497
  • Country: hu
  • æðsta yfirmaður
  • OS:
  • Linux (Ubuntu) Linux (Ubuntu)
  • Browser:
  • Firefox 37.0 Firefox 37.0
    • View Profile
    • http://lgb.hu/
Re: 6Mhz and more...
« Reply #31 on: 2015.April.10. 14:58:50 »
Z80, which always runs at half the clock frequency of DAVE

Ah, thanks.

Online gflorez

  • EP addict
  • *
  • Posts: 2668
  • Country: es
  • OS:
  • Windows XP Windows XP
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
Re: 6Mhz and more...
« Reply #32 on: 2016.December.13. 18:07:20 »
One of the two Z80As removed with zero victims....

Online gflorez

  • EP addict
  • *
  • Posts: 2668
  • Country: es
  • OS:
  • Windows XP Windows XP
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
Re: 6Mhz and more...
« Reply #33 on: 2016.December.14. 11:56:22 »
What a mystery!

On the Enterprise mainboard, a  track from Z80 pin3(A13) to pin B10 on the Cart Bay is provided, but cut on two places.

Then, a black lead has been welded directly at final production. Why?



(There is an error on the cartridge bay pinout at Zozo's information web page, B10 should be A13, not A12.)

Online Zozosoft

  • EP addict
  • *
  • Posts: 13534
  • Country: hu
  • OS:
  • Windows XP Windows XP
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
    • http://enterprise.iko.hu/
Re: 6Mhz and more...
« Reply #34 on: 2016.December.14. 12:24:34 »
track from Z80 pin3(A13) to pin B10
To B7. (B1 are the upper left)

Why?
Good question, I also want to know the answer!

On ISSUE3 boards are hand cutted these, on later boards cut done on the PCB producing films.

Quote
(There is an error on the cartridge bay pinout
:oops: :oops: :oops: Two A12... Now fixed.

Online gflorez

  • EP addict
  • *
  • Posts: 2668
  • Country: es
  • OS:
  • Windows XP Windows XP
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
Re: 6Mhz and more...
« Reply #35 on: 2016.December.14. 17:10:20 »
Good question, I also want to know the answer!

Maybe some sort of unknown interference forced them to modify the plans. Like the glitches found by Bruce Tanner  on the signals, while testing his modern oscilloscope.

Online gflorez

  • EP addict
  • *
  • Posts: 2668
  • Country: es
  • OS:
  • Windows XP Windows XP
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
Re: 6Mhz and more...
« Reply #36 on: 2016.December.20. 17:44:21 »
I have successfully modified one of my EPs following Zozo's hints.

This is the tasks list:

-Installed a "programmable in situ" 128K AMD FlashRom with a switch to select between the two 64K banks. The last version of EXOS has been programmed on the two banks.

-Un-welded the original Z80A clone and installed a Z84C0020 on a socket.

-Followed the overclocking procedure in this same thread, that implies:
     -Separated the processor clock signal from the system clock frequency.
     -R12 short-circuited
     -C7 opened
     -Added a pull-up resistor array on the Z80 data bus.
     -Installed a 20Mhz clock crystal to drive the processor.
     -Installed a 74LS157 to select between 8Mhz and 20Mhz(halved frequency on the Z80) while the computer is running.
     -Put a switch to make the selection.
     -One of the commutations of the switch has been also used to select the colour of the main power Led.  

This EP had already a 1MB Saint Ram expansion installed, and the task remaining to me is to remove the two 7805 regulators and install instead two 2A Traco-power that I am still waiting.

Once closed I hope not have to re-open this computer ever again...
« Last Edit: 2016.December.20. 17:50:45 by gflorez »

Offline geco

  • EP addict
  • *
  • Posts: 5430
  • Country: hu
  • OS:
  • Linux Linux
  • Browser:
  • Firefox 45.0 Firefox 45.0
    • View Profile
Re: 6Mhz and more...
« Reply #37 on: 2016.December.20. 19:00:46 »
Congrat :) I could not do it myself.

Online Zozosoft

  • EP addict
  • *
  • Posts: 13534
  • Country: hu
  • OS:
  • Windows NT 10.0 Windows NT 10.0
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
    • http://enterprise.iko.hu/
Re: 6Mhz and more...
« Reply #38 on: 2016.December.20. 19:20:30 »
Great work!
    -Installed a 74LS157 to select between 8Mhz and 20Mhz(halved frequency on the Z80) while the computer is running.
It is working for you with 74LS? For me the LS only enought for 7.12 MHz (14 MHz system clock), for the 10MHz (20MHz system) needed to use 74F. As I recomended here.

Offline ergoGnomik

  • EP lover
  • *
  • Posts: 841
  • Country: hu
  • Stray cat from Commodore alley
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Opera 12.17 Opera 12.17
    • View Profile
Re: 6Mhz and more...
« Reply #39 on: 2016.December.20. 19:33:46 »
/OFF

Hi gflorez,

Excuse me, for looking a bit like I'm talking down to you. I really don't want to anger you or hurt your feelings in any way, but could you please give a thought to using solder instead of weld? Somehow it really disturbs me. Unless it is a common joke I never knew.

/ON

Online gflorez

  • EP addict
  • *
  • Posts: 2668
  • Country: es
  • OS:
  • Windows XP Windows XP
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
Re: 6Mhz and more...
« Reply #40 on: 2016.December.20. 19:52:10 »
/OFF

Hi gflorez,

Excuse me, for looking a bit like I'm talking down to you. I really don't want to anger you or hurt your feelings in any way, but could you please give a thought to using solder instead of weld? Somehow it really disturbs me. Unless it is a common joke I never knew.

/ON


Sorry, as a not native English writer, I thought that the two words mean the same....


Edit: By the way, in Spanish the two English meanings are joined on the same word, "soldar, soldadura", but when there are several possible English words to choose I tend to use the most different word (from Spanish) to not fall in the error of creating a new "Spanglish" word....
« Last Edit: 2016.December.20. 20:07:04 by gflorez »

Online gflorez

  • EP addict
  • *
  • Posts: 2668
  • Country: es
  • OS:
  • Windows XP Windows XP
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
Re: 6Mhz and more...
« Reply #41 on: 2016.December.20. 19:59:13 »
Great work!It is working for you with 74LS? For me the LS only enought for 7.12 MHz (14 MHz system clock), for the 10MHz (20MHz system) needed to use 74F. As I recomended here.


I am only connecting the card, so it doesn't pass the flashing letters, (not having a keyboard) but it returns and go from the slow letters to the fast letters without problem.

I will buy tomorrow the 74F chips, thanks.

Online Zozosoft

  • EP addict
  • *
  • Posts: 13534
  • Country: hu
  • OS:
  • Windows NT 10.0 Windows NT 10.0
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
    • http://enterprise.iko.hu/
Re: 6Mhz and more...
« Reply #42 on: 2016.December.20. 20:39:24 »
I am only connecting the card, so it doesn't pass the flashing letters, (not having a keyboard) but it returns and go from the slow letters to the fast letters without problem.

I will buy tomorrow the 74F chips, thanks.

If it is working, then not needed replace it. When I tried it, system totaly don't run on the 10MHz with the LS chip. But probably because I used 20-30 years old 74LS from spares, and you used new one.

About the words: in Hungarian are also different: forraszt (solder), hegeszt (weld).

Online pear

  • EP lover
  • *
  • Posts: 786
  • Country: pl
  • Z80 only
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
Re: 6Mhz and more...
« Reply #43 on: 2016.December.20. 20:44:14 »
About the words: in Hungarian are also different: forraszt (solder), hegeszt (weld).
The Polish also: lutowanie (soldering) and spawanie (welding).

Online gflorez

  • EP addict
  • *
  • Posts: 2668
  • Country: es
  • OS:
  • Windows XP Windows XP
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
Re: 6Mhz and more...
« Reply #44 on: 2016.December.20. 20:52:55 »
It's a miracle that we can understand the others....