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General Category => Amstrad CPC hardware => Topic started by: balford on 13:58, 27 October 21

Title: CPC 464 prototype with Gate Array simulator board found
Post by: balford on 13:58, 27 October 21
Anyone who's on FB should take a look at the following link (closed group, so you may need to join):
Amstrad CPC 464 group - prototype CPC (https://www.facebook.com/groups/5357712057/?multi_permalinks=10158945814752058)

I've suggested the guy loans the machine to someone with expertise in reverse engineering the Gate Array simulator board, as far as I know it hasn't been done yet?

He intends auctioning it, so the more people who can suggest alternatives to stop it falling immediately out of public view the better!
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Gryzor on 14:56, 27 October 21
Oh damn. I'm salivating. So what, start a wiki fund or something? Sure, why not. And then... what?
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: rastislavz on 15:02, 27 October 21
Exactly that was what I have suggested in the FB thread that we could fund it together.
Than somebody wise can analyse the board and make the ULA simulator on FPGA like similar custom chip replacements were made for other 8-bits, e.g. commodore.
The unit could be donated to some retro computer museum.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: TotO on 15:10, 27 October 21
@gerald (https://www.cpcwiki.eu/forum/index.php?action=profile;u=250) is called here.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Gryzor on 15:22, 27 October 21
Quote from: rastislavz on 15:02, 27 October 21The unit could be donated to some retro computer museum.
...and that's where the problem begins, probably...

I'm all for it, though. There are places where we can raise a common fund, once we agree on the administrator of the fund.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Gryzor on 15:23, 27 October 21
Oh well, never mind, it's already on ebay and with a 3-day limit *repeatedly slaps forehead*

Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: TotO on 15:25, 27 October 21
<< this post can be deleted >>
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: balford on 15:57, 27 October 21
Disappointing outcome. Hopefully it goes to someone who won't hide it away.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Gryzor on 15:57, 27 October 21
Wouldn't hold my breath :(
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: rastislavz on 16:48, 27 October 21
Quote from: Gryzor on 15:23, 27 October 21
Oh well, never mind, it's already on ebay and with a 3-day limit *repeatedly slaps forehead*
Yeah 3 days is not much time to organize something... Guy wants to become rich as fast as possible. Its a pitty. These things usualy end up on somebodys shelf behind the glass.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: eto on 17:24, 27 October 21
Quote from: balford on 13:58, 27 October 21I've suggested the guy loans the machine to someone with expertise in reverse engineering the Gate Array simulator board, as far as I know it hasn't been done yet?

As Roland Perry pointed out on FB, there are plenty of PLA chips, so even with this model, it's not easy to reverse engineer the Gate Array.

I was wondering, how compatible the KC Compact is. If I am not mistaken, the GDR engineers already did reverse engineer the Gate Array and replicated it with standard logic chips. WOuldn't that be a much easier way to reverse engineer the logic of the Gate Array? Except for the Gate Array they used either the original chips or clones, so I would expect, that their Gate Array logic should be close to identical.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: gerald on 18:14, 27 October 21

Quote from: TotO on 15:10, 27 October 21
@gerald (https://www.cpcwiki.eu/forum/index.php?action=profile;u=250) is called here.
shout louder ! Notification does not seem to work   ;D
Quote from: eto on 17:24, 27 October 21As Roland Perry pointed out on FB, there are plenty of PLA chips, so even with this model, it's not easy to reverse engineer the Gate Array.
Yes, at least 9 of them. But if these are just PAL (not using registers) it should be doable. With registers it will just make it a bit more complicated.
However the SOLD AS SEEN UNTESTED (MAY NOT WORK) is a big showstopper for me.


Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: eto on 18:20, 27 October 21
Quote from: gerald on 18:14, 27 October 21Yes, at least 9 of them. But if these are just PAL (not using registers) it should be doable.

Have you ever thought about using the schematics of the KC compact? I had a quick look and it doesn't look like they have any PAL but only (many) standard logic ICs.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: gerald on 19:03, 27 October 21
Quote from: eto on 18:20, 27 October 21Have you ever thought about using the schematics of the KC compact? I had a quick look and it doesn't look like they have any PAL but only (many) standard logic ICs.
I must confess, I never look at the KC compact  :picard:
A quick look show that it is not an exact emulation of the CPC GA. Interrupt are coming from a z8536, mode 3 is different as well as some other bits (https://www.cpcwiki.eu/index.php/KC_Compact#Hardware_differences)

On the schematic, you can also see that they are using a 2716 eeprom as a PAL equivalent.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: TotO on 20:05, 27 October 21
I think the Aleste 520 schematic is better for that.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: xesrjb on 20:43, 27 October 21
At last jesus6128 Ebayer from Spain will get it for 1000 £...


xesrjb
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Gryzor on 21:05, 27 October 21
Something like that probably...
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: TotO on 22:17, 27 October 21
The item condition will probably require to be fixed to work again if no issue from the GA board.
Sad to see the keyboard missing a key and was not the original. The same for the bottom case.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: dragon on 00:22, 28 October 21
I'm not in the Facebook  group someone can put pictures?
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Richard_Lloyd on 00:45, 28 October 21
https://www.ebay.co.uk/itm/384467604011?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649


Over £400 already........
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Richard_Lloyd on 00:53, 28 October 21
https://www.theregister.com/Print/2014/02/12/archaeologic_amstrad_cpc_464/


The photos in this article have different coloured base and front just like the one for sale.......
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: 00WReX on 12:40, 28 October 21
Quote from: TotO on 22:17, 27 October 21
The item condition will probably require to be fixed to work again if no issue from the GA board.
Sad to see the keyboard missing a key and was not the original. The same for the bottom case.
I think the bottom of the case is original. I have seen two others and they are the same. The key thing is that the production models had 5V 2A on the sticker...the development have 5V 1.5A.

Cheers,
Shane
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Gryzor on 12:42, 28 October 21
Well, Perry says it's not an original, based on the label...
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: 00WReX on 12:45, 28 October 21
Quote from: Gryzor on 12:42, 28 October 21
Well, Perry says it's not an original, based on the label...


He actually acknowledged what I said...


"Thanks for that information. There must be two generations of grey 464 - because I've seen ones without the black label on the base."
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Gryzor on 13:25, 28 October 21
Missed that comment. However that looks like a production label, it'd be weird if it belongs to a prototype, especially since other labels and markings are paper, half glued ones.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: rastislavz on 13:41, 28 October 21
Quote from: gerald on 18:14, 27 October 21However the SOLD AS SEEN UNTESTED (MAY NOT WORK) is a big showstopper for me.
I do not see that very tragic, thw guy is just scrap reseller so it does not know how and it does not want to test it, but the internals looks untouched, I think there is very high chance it may still work taking into account how sturdy these machines are in general. But I completely understand investing such huge ammount of money is quite risky.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: rastislavz on 13:45, 28 October 21
On Noels Retrolab discord I have offered him donation if he wins it. It would make a very nice video about it I am sure and would analyze it deeply. So if somebody else is willing to donate some money to him let him know on his discord.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Z|G on 16:07, 28 October 21
up $1500 pounds in less than 6 hrs (was $555 pounds, sitting @ $2000 pounds)....

any bets on where the price will finish up on  :D
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: dragon on 20:49, 28 October 21
It have a  AM29705APC why they need ram?. .


Also it have lost one part of the board the part with the eeproms. (from the other eBay prototype).
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: gerald on 21:48, 28 October 21
Quote from: dragon on 20:49, 28 October 21
It have a  AM29705APC why they need ram?. .
It's  a 16 x 4bit dual port RAM. I guess it is used to store the ink configuration (but we miss 1 bit and the full border)
The ink / border registers are using about 70% of the gate array

Quote from: dragon on 20:49, 28 October 21
Also it have lost one part of the board the part with the eeproms. (from the other eBay prototype).
The EPROM side seems to be 4*2732 to emulate a 27128. Here we have a 27128 on the main board.


Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: dragon on 23:08, 28 October 21
And in the left part they have hc chips and in the rest of the board ls chips.


I remember from the asignature of University(middle pc assembly/part of basic logic gates, karnaugh maps and  made a prototype board with her switch bus leds and so).


Don't mix hc and ls ics.. Don't mix hc and ls ics.


Well finally don't matter, we have a list of ics and in the shop.. oh I only have these in hc or I have only these in ls, or I don't have the but we have these another equivalent.


Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: 1024MAK on 12:05, 29 October 21
74LSxxx chips and 74HCxxx can be mixed, but with restrictions and limitations.

A 74HCxxx output pin can drive a 74LSxxx input without any problems.

74HCxxx use CMOS switching levels on their input pins, not TTL levels.

As 74LSxxx (and the earlier 74xxx, 74Sxxx) chips have TTL outputs, for any of these to drive a 74HCxxx, a pull-up resistor should be used. But a low value pull up resistor is needed for high speed operation, increasing power consumption. And this may not work at very high speeds due to stray capacitance.

Because of these problems, the 74HCTxxx range was introduced. These are still CMOS chips. They have the same outputs as 74HCxxx chips. But have inputs that are compatible with 74LSxxx outputs.

Mark
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: retro_4_ever on 16:15, 30 October 21
£3092.00 wow !!!!! hope it ends up in noels retro lab ... 
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: TotO on 17:13, 30 October 21
I don't even want to imagine how much the final price would have been with the original keyboard and lower case, in working condition...  :laugh:
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: retro_4_ever on 17:53, 30 October 21
how do you if the keyboard & case are not original ? should the bottom be grey as well ?
i did notice it was rated at 1.5amp on the bottom of the case, something i have not seen on any 464
and the keyboard was the same as the early productions models
when i first saw it i thought maybe £300 - £500 but 3K .. just wow !!!
i wonder how many of these were made and how many could still exist today

Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Bryce on 15:05, 31 October 21
As far as I know, the bottom of the prototype cases always had the dark grey colour. There was never a beige lower case.
Assuming normal prototype runs of the time for a device of this type, I'd guess there were probably 15 to 20 of these built.

Bryce.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: dragon on 15:39, 31 October 21
I remember read about 50 in Google News. Probably same as software houses that program initially from the cpc.




And maybe exist some early prototype. In the spanish book of jose luis dominguez.  When he talk about how he promise to amstrad made poogaboo and Roland in the ropes. He talk that amstrad give it a computer that not appear a computer. He made in trouble in customs to explain thas was a computer, because was a mixture of wires. And appear pure trash.


These prototype appear a computer.

Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Gryzor on 17:03, 31 October 21
I think Perry said 20?
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Bread80 on 18:41, 31 October 21
Well, these were examples sent to software houses to create software on. So, I'd argue, more of a 'preproduction' model than a prototype.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Gryzor on 18:48, 31 October 21
Hmm an interesting point... In that light a prototype would be a wire board thing or in our case even the 6502 model
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: dragon on 20:32, 31 October 21
Quote from: Gryzor on 17:03, 31 October 21
I think Perry said 20?


You have lost the number "21" in the eBay computer. XD.


I'n the book is mentioned the even the ctm was a some type of strange prototype. Witouth frame.

 
https://groups.google.com/g/comp.sys.amstrad.8bit/c/QG-66_23rXY/m/JmVUNSlC7bMJ

Cliff Lawson write 50
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: TotO on 21:14, 31 October 21
Quote from: retro_4_ever on 17:53, 30 October 21
how do you if the keyboard & case are not original ? should the bottom be grey as well ?
i did notice it was rated at 1.5amp on the bottom of the case, something i have not seen on any 464
and the keyboard was the same as the early productions models
Because Roland Perry has said that. A shame to have replaced the original keyboard (gray keys like the tape buttons) with a new one. And the fact that prototypes CPC do not have hte metalic label under the case but a paper label.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: eto on 21:23, 31 October 21
Quote from: TotO on 21:14, 31 October 21And the fact that prototypes CPC do not have hte metalic label under the case but a paper label.


In a later discussion he acknowledged that "There must be two generations of grey 464 - because I've seen ones without the black label on the base.".

So the base might be from an original prototype.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: TotO on 23:29, 01 November 21
I don't understand this sentence like an acknowledgment from him, but more the fact that he has only seen prototypes with paper label, so if this one is original, that mean there must be two generations of grey 464. I think that modern keyboard explain the back casing.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: dragon on 05:00, 02 November 21
If you come back to 2019 in Facebook group  Roland Perry upload the road of cpc 464 development.




The document tell hardware design mej


4-5 1st prototype


5-7 2nd-5nd prototypes


7-9 gate array cad


9-12 50 test units specify made.


So it appear they made five prototypes. Pre-gate array simulator board.

Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Bryce on 10:00, 02 November 21
Quote from: dragon on 05:00, 02 November 21
If you come back to 2019 in Facebook group  Roland Perry upload the road of cpc 464 development.




The document tell hardware design mej


4-5 1st prototype


5-7 2nd-5nd prototypes


7-9 gate array cad


9-12 50 test units specify made.


So it appear they made five prototypes. Pre-gate array simulator board.

That sounds like a completely normal development cycle for something like this.

Bryce.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Joseman on 00:34, 29 November 21

Hi I saw this on twitter


https://twitter.com/retro_nazi/status/1465025249632821254?t=1xxRQB2UiSgwJgllZY9Hdw&s=08
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Gryzor on 09:33, 29 November 21
Damn all I got on black Friday was a sweater.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Joseman on 21:39, 29 November 21
That Gate Array board, is the best option to clone de GA?
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: gerald on 09:29, 30 November 21
I have a working GA replacement, unfortunately component availability problem just can't make it happen ... yet  ;)
https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/a-minimal-gate-array/msg198585/#msg198585
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: eto on 10:42, 30 November 21
And here a user replicated the Gate Array using 2 Raspberry Picos: https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/creating-a-replacemant-gate-array/


Not released yet, but it looks also very promising.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: Joseman on 11:24, 30 November 21
Quote from: gerald on 09:29, 30 November 21
I have a working GA replacement, unfortunately component availability problem just can't make it happen ... yet  ;)
https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/a-minimal-gate-array/msg198585/#msg198585 (https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/a-minimal-gate-array/msg198585/#msg198585)
great!
and is 100% accurate or that board will help to understand something missing?
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: TotO on 15:16, 30 November 21
Quote from: Joseman on 21:39, 29 November 21
That Gate Array board, is the best option to clone de GA?
Not at all, because it doesn't work exactly like the final product.
The best is the retro-engeenering from the commercial version done by gerald.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: ralferoo on 17:28, 01 December 21
Quote from: gerald on 18:14, 27 October 21Yes, at least 9 of them. But if these are just PAL (not using registers) it should be doable. With registers it will just make it a bit more complicated.
However the SOLD AS SEEN UNTESTED (MAY NOT WORK) is a big showstopper for me.
It's pretty hard to extract the configuration data out of a PLA IIRC, so even if you know the exact chip that was used and have the datasheet, it might not do you much good.

I'm not sure there's all that many secrets left in the GA though... I remember when doing my FPGA-based emulator, I was convinced the _WAIT logic was really complicated, after having a long argument with someone who was doing a software emulator (I forget who now) and trying out what they said, I discovered they were right and the really simple way also yields exactly the same timing weirdnesses. (Although checking my code now shows I kept my overly complicated logic involving different rules that handles _IORQ and _MREQ differently depending on _M1, but I can't remember why now, probably just because it also seemed to work on everything I'd tried).

I think the most complicated logic in the entire gate array is the colour palette decoding, as it seems quite horrible and arbitrary, but when I sat down for a couple of hours with pen and paper and analysed the logic patterns I ended up with something pretty simple. Digging out the snippet from my code:

        r_v     <= '1' when col(3)='1' or (col(4)='0' and col(0)='1') else '0';
        r_oe    <= '1' when (col(4)='1' and col(3)='1') or (col(4)='0' and col(3)='0' and col(2)='0' and col(1)='0') else '0';

        g_v     <= '1' when col(2)='0' and (col(1)='1' or col(0)='1') else '0';
        g_oe    <= '1' when (col(2)='1' and col(1)='1') or (col(2)='0' and col(1)='0' and col(3)='0' and col(4)='0') else '0';

        b_v     <= col(0);
        b_oe    <= '1' when (col(4)='0' and col(3)='0') or (col(2)='0' and col(1)='0') else '0';


Where _v is the high/low output on the pin, _oe is the output enable, when it's 1 the pull-up/pull-down resistor combo leave the pin floating at half voltage.

I also made similar discoveries with this when I really sat down to think about how I'd implement the sound chip in as few gates as possible. My entire AY8912 implementation was in the order of 300 gates, and smaller than most implementations use for their volume lookup table! (And it emulated the bugs in the real chip too, which is always a bonus!)

Extra detail: unlike every other implementation which use an 8-bit DAC, the output of my AY8912 implementation was a single-bit DAC that was then smoothed with a small capacitor. The volume response sounded identical to compared to all the complicated software versions with their fancy lookup tables, but I'm not hard-core audiophile enough to know if it sounds exactly the same to everyone else! But I was running that at 16MHz and IIRC the real chip only takes a 1MHz clock, so I probably wasn't doing it exactly the same.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: ralferoo on 17:43, 01 December 21
Quote from: eto on 10:42, 30 November 21And here a user replicated the Gate Array using 2 Raspberry Picos: https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/creating-a-replacemant-gate-array/

This seems kind of excessive. There's probably more logic in the power-control circuitry on the RPi than the entire GA it's emulating!
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: eto on 20:02, 01 December 21
Quote from: ralferoo on 17:43, 01 December 21There's probably more logic in the power-control circuitry on the RPi


Raspberry Pico, not Raspberry Pi





Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: ralferoo on 22:07, 01 December 21
Quote from: eto on 20:02, 01 December 21
Raspberry Pico, not Raspberry Pi
My argument is probably still true, but yeah I'd overlooked the fact that at least it's the embedded controller thingy and not a Pi.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: pelrun on 05:10, 02 December 21
I don't understand the desire for "gate efficiency" - when the hardware in question is $1, does it really matter if half the gates in it are unused? All the alternatives cost far more - and that's an actually useful metric compared to something that's effectively unmeasurable.
Title: Re: CPC 464 prototype with Gate Array simulator board found
Post by: TotO on 10:20, 02 December 21
I think the idea was to use disproportionate measures to reach the goal.
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