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Messages - gflorez

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Hardware / Re: Capacitors - wrong orientation?
« on: 2020.October.13. 10:31:22 »
Not so long ago Tutus was honoured to ask Nick Toop some questions.

On his answer he narrates how painfully was his exit from Enterprise Computers LTD:

".....when I was constructively forced out of the company was one of the saddest periods of my life and I do not like to think about it.  I was also obliged to erase all personal copies of the design which is sad as I had various enhancements in mind and would love to be able to implement my design with these enhancements in a modern CPLD...."

This mean to me that all people involved on the project had such obligatory clause in their contracts.

Hardware / Re: Enterprise Deployment Attempt Over FPGA.
« on: 2020.October.12. 20:31:20 »
Sorry, this one is loading from TAPE:

Hardware / Re: Enterprise Deployment Attempt Over FPGA.
« on: 2020.October.12. 20:22:46 »
Another video, loading a Basic listing(still without audio):

Hardware / Re: Enterprise Deployment Attempt Over FPGA.
« on: 2020.October.12. 13:04:05 »
Yes... Zozo's routines to calculate the Z80 frequency need correct interrupts. The real clock in the video is 3.5Mhz.

Hardware / Re: Capacitors - wrong orientation?
« on: 2020.October.12. 09:32:13 »
Remember its first name: Damp Proof Course.

The first phases of development were strictly secret....

Interface / Re: Internal memory expansion
« on: 2020.October.12. 09:08:55 »
I can think at least on two good reasons to have 1MB of Ram on the EP:

First, because the amazing SymbOS can manage all that memory.

And second, because there has always been the challenge of knowing if it would be possible for EXOS to reach the maximum of 4MB of addressable memory that was promised....

Interface / Re: Internal memory expansion
« on: 2020.October.11. 18:52:21 »

Yess, it is a wonderful heritage.....

Hardware / Re: ZX Spectrum Emulator Card
« on: 2020.October.11. 18:48:28 »
Maybe it is time to also move the Z80 ports....

And also to adapt the Gohs Rom would be great.

Hardware / Re: Capacitors - wrong orientation?
« on: 2020.October.10. 23:17:34 »
If the Issue 3 were only 100... maybe these were the prototypes, no more than 10 or so.

Interface / Re: Internal memory expansion
« on: 2020.October.10. 20:44:39 »

I think that the case will fit if you bend a little the EXP2 leads to the left. The eight of the piggy-back Ram chips is the same as the ones on the Saint's Ram expansions I have installed on my EPs, so that will not be a problem.

Hardware / Re: Capacitors - wrong orientation?
« on: 2020.October.10. 19:23:10 »
Zozo can say all about that.

What I have read from him is that ALL EP PCBs share the same circuit layout, with minor differences on the "fingers" of the EDGE connectors.

Starting from bottom, issue 3, 4 and 5 on the middle, and 6 the upper one.

The Issue 3 EDGE fingers were totally wrong, with excessive width, prone to cause short-circuits if not correctly aligned with the female connector . A bigger gap was added on issues 4 and 5 to fix that, and on issue 6 some of the unused pins of the Video connector were populated and gained a solder point, the planed use unknown.

There are also some differences on the custom chips mounted. Issue 3 were test EP64s fitted with Korean made Nick and Dave, first batches of chips that turned out to be malfunctioning, needing an external PCB to correct the behaviour. There are very few of these, almost all distributed to developers, not to open public.  

Issues 4 and 5 mount the first batches of Austrian made custom chips, but it happened that the advanced designs were years ahead of the contemporary manufacturing techniques, and then the new Nick also didn't worked as intended. It showed bad colours on some intensive screen modes(and probably bad external colour input), some units worse than others. The cooper heat sink over Nick was then added to minimize the failure, worse on high temperature.

The new fixed Nick was introduced with the Issue 6 PCBs or a little earlier on last Issue 5.

There are other curiosities about the Enterprise PCBs, the most evident is the black lead from the Z80 to the cartridge port that can be seen on the upper side... the same cooper track already exist on the PCB, but cut on two places(on all EPs), a modification probably made to fix some insidious signal interference.

Hardware / Re: Capacitors - wrong orientation?
« on: 2020.October.10. 11:21:36 »
Hello Elmer.

About serial numbers, I don't know if you have took a look to the inventory of machines from Zozo's page.

On it you can observe how the EP64 numerations are different from the EP128 ones. You also can see how there are very big gaps on the EP64 list.

EP64 numbers 2000~30000, probably all expanded to 128KB by the Enterprise company, that could explain why there are so many issue 4 and 5 PCBs mixed with issue 6 ones, the usual on the 128KB EP.(There are also some issue 6 EP64s, probably refurbished in Germany and then sold to the Egypt dealer).

EP64 numbers 40000~70000...., I have a theory for this gap... at that time they were selling less Enterprise units than expected and, incrementing artificially the serials, then could give to the public impression that they had manufactured a huge amount.

I think that they restarted the serial count for the EP128 model, now lineal, the first units being mounted with the rest of old issue 4 and 5 PCBs with the defective Nick(mine for example), and then all the rest issue 6 PCBs with the improved Nick.

Memória / Re: 512K belső RAM bővítés - II
« on: 2020.October.09. 20:07:59 »
The language barrier is to overcome it.

Yes, you are right. Is for that I usually write here a double message in Hungarian/English, even when I am Spanish...

But when Google fails to translate technician terms then I opt for English only.

Memória / Re: 512K belső RAM bővítés - II
« on: 2020.October.09. 20:03:58 »
Pear also wants to gift some of these little PCBs, talk with him.

Interface / Re: Internal memory expansion
« on: 2020.October.09. 14:56:29 »
Great! the second internal Ram expansion on the same week...

I think that Pear's L-connector solution for the EXP2 header can suit perfectly your project.

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