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Author Topic: 6Mhz and more... (Read 25478 times)

Offline jltursan

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Re: 6Mhz and more...
« Reply #15 on: 2014.June.19. 16:24:20 »
Issue 5 then :smt045

Offline jltursan

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Re: 6Mhz and more...
« Reply #16 on: 2014.June.27. 19:22:41 »
I'm going to try to fix the RAM segment failures. Just to be sure, the pullup resistors are 4K7?

Offline Zozosoft

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Re: 6Mhz and more...
« Reply #17 on: 2014.June.27. 20:39:21 »
Quote from: jltursan
 Just to be sure, the pullup resistors are 4K7?
Yes.

Offline jltursan

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Re: 6Mhz and more...
« Reply #18 on: 2014.September.11. 11:09:27 »
Btw, just a quick update, I'd finally used a 16Mhz oscilator, looks like the 20Mhz was too much for my enterprise. Running at 10Mhz the computer was fine; but some floppies stutter a lot and even a few of them doesn't load at all (I suposse they need to be formatted and written at this speed). Also a lot of games shown sync artifacts and, of course, the ones working fine run too fast :-D

Offline Zozosoft

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Re: 6Mhz and more...
« Reply #19 on: 2014.September.11. 11:28:02 »
It is need more wires and switches: build a multi-trubo system.
My machine can run on 4, 6, 7.12, 10 MHz speeds, can be selectable with switchs.

Which EXDOS card are you using?

For a higher CPU speed I recommend replace the old 74LS ICs to 74HCT, EPROM to fast CMOS one or Flash ROM, and if the WD are old 1770 then replace with 1772.
WD1772 PH 02-02 have a "enhanced digital data separation" then it is more reliable about disk reading.
And with 1772 chip can be used fast floppy step rates, then the drive will work faster and quiet.

Offline jltursan

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Re: 6Mhz and more...
« Reply #20 on: 2014.September.11. 11:59:47 »
Indeed, I followed your suggestions and mine can run at normal/turbo speed selectables with a switch and with a multicolor led :). Do you have a pair of oscillators (12Mhz & 20Mhz)? :shock:

My EXDOS card is the original one:



The EPROM is already replaced; but other ICs are unchanged. The 1772 is pin compatible with the 1770?, maybe I can try with that...
Also, what about the 3 x 7438, how they can be replaced by faster ICs?

Offline IstvanV

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Re: 6Mhz and more...
« Reply #21 on: 2014.September.11. 12:07:07 »
Quote from: jltursan
Also a lot of games shown sync artifacts and, of course, the ones working fine run too fast :-D
Try my Freescape ports like Castle Master, Total Eclipse and others. These games can always make use of the extra CPU speed. :) But the sound will only be correct at 4 and 6 MHz, above that the pitch will be too high.

Offline Zozosoft

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Re: 6Mhz and more...
« Reply #22 on: 2014.September.11. 12:08:22 »
Quote from: jltursan
The 1772 is pin compatible with the 1770?
Yes.
Quote
Also, what about the 3 x 7438, how they can be replaced by faster ICs?
These not important to replace, used as line driver on floppy cable.
Data bus driver (U3) and address decoding ICS (U5,6,7,8,9) are the important.

Offline Zozosoft

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Re: 6Mhz and more...
« Reply #23 on: 2014.September.11. 12:10:55 »
Quote from: IstvanV
These games can always make use of the extra CPU speed.
Also try the Race Ace: the computer cars are synchronized with the video interrupt, only your car got a super speed! :ds_icon_cheesygrin:

Offline jltursan

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Re: 6Mhz and more...
« Reply #24 on: 2014.September.11. 12:29:57 »
Thanks istvanV & Zozosoft for the suggestions!. That freescape ports looks like a great candidate to test the speed :twisted:
I also want to try the VIC-20 emulator, it would be great to speed up the emulation close to the real VIC speed.

Quote
These not important to replace, used as line driver on floppy cable.
Data bus driver (U3) and address decoding ICS (U5,6,7,8,9) are the important.

Mmm; so I'll try to socket the controller and U5-9 and replace them with their faster HCT equivalents. I need to be careful with that, the EXDOS controller is by now, my most valuable piece of Enterprise software :)
Btw, in a spanish forum, we're trying to clone the EXDOS controller: Controladora de disco para Enterprise
It's only in spanish, sorry. Also, the forum engine is a bit retrictive and links are not shown to unregistered users :(; but I'll be happy to give you all details about the development.

Offline Zozosoft

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Re: 6Mhz and more...
« Reply #25 on: 2015.April.08. 23:33:30 »
Two 4 speed (4/6/7.12/10 MHz) machines for Prodatron:
12259-012261-1
12263-212265-3
12267-412269-5

Offline Ep128

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Re: 6Mhz and more...
« Reply #26 on: 2015.April.10. 00:13:27 »

Offline lgb

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Re: 6Mhz and more...
« Reply #27 on: 2015.April.10. 11:44:37 »
How CPU clock is switched? Can be controlled from software, or some kind of actual switch?

Offline Zozosoft

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Re: 6Mhz and more...
« Reply #28 on: 2015.April.10. 13:14:09 »
Just two simple switchs, which make a 2 bits selection on the 74F153.

Offline lgb

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Re: 6Mhz and more...
« Reply #29 on: 2015.April.10. 14:14:40 »
Ok then, another white spot for me: It seems designers of EP already thought about the "turbo", namely 6Mhz, as Dave can be configured for that to have timings intact. However I always felt it's not a good solution as softwares can have the bad habit to write  their thought-to-be-correct value to the corresponding Dave port. 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? Because if it's 7.12Mhz is much more useful and "compatible" (well, of course there can be other problems like software can require 4MHz CPU clock to work correctly, etc) than the 6MHz planned mode by the designers.