Imagine if Commodore

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Gyro Gearloose
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Imagine if Commodore

Postby Gyro Gearloose » Sun Jan 07, 2018 5:37 pm

had scratched off the part numbers from all the chips on the VIC-20, and didn't publish the full schematics for us to use?

Yeah, terrible, right?

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Re: Imagine if Commodore

Postby norm8332 » Sun Jan 07, 2018 6:44 pm


eslapion
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Re: Imagine if Commodore

Postby eslapion » Sun Jan 07, 2018 7:15 pm

:shock:

Next post will be the fusemap ?
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Re: Imagine if Commodore

Postby norm8332 » Sun Jan 07, 2018 10:10 pm

Total guess...the pins are tinned though so probably a Chinese source. He said It was a PLD before and 16v8 is very common, cheap and 128K Hitachi chip is cheap and both chips pins match. I'd say it's partly based on the public schematic I posted including using the 10K pullups. http://sleepingelephant.com/ipw-web/bulletin/bb/viewtopic.php?f=11&t=8764&p=98145#p98145 He just used additional logic and a single 128K chip that has enough address lines I bet.

I was previously thinking of designing and releasing the PCB etc. to PD for one like that with the 128K chip but I was going to use 74xx chips since I have a lot of those.

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Re: Imagine if Commodore

Postby eslapion » Mon Jan 08, 2018 8:09 am

norm8332 wrote:I was previously thinking of designing and releasing the PCB etc. to PD for one like that with the 128K chip but I was going to use 74xx chips since I have a lot of those.

Be careful there. You may be in for a 'paternity' test! :lol:

The funny thing is, the RAM chip is half the price of new chips 32k x 8 SRAM chips but the GAL is double the price of a CPLD like the XC9536XL used on PLAnkton but I guess it's not adequate for him since it doesn't signal at 0-5V...

Use a pair of new 74LSxx along with new SRAM and you don't even need resistors anymore and the total price for the parts is less than the GAL alone!
Last edited by eslapion on Mon Jan 08, 2018 12:11 pm, edited 1 time in total.
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Re: Imagine if Commodore

Postby groepaz » Mon Jan 08, 2018 8:34 am

somehow seeing ppl arguing over this trivial stuff is cute <3

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Re: Imagine if Commodore

Postby norm8332 » Mon Jan 08, 2018 8:40 am

Its not an argument it's a debate and yes it's trivial :)

That link is for qty 10 GALs.

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Re: Imagine if Commodore

Postby eslapion » Mon Jan 08, 2018 12:10 pm

norm8332 wrote:That link is for qty 10 GALs.

Had overlooked that detail so the BOM total price tag is around 1.50$. No wonder you'd want to scratch off the part numbers.

Add to this dirt cheap FR4 boards devoid of any plating... what was the selling price tag ?
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Re: Imagine if Commodore

Postby Floopy » Mon Jan 08, 2018 12:40 pm

I only buy passive components from China. NEVER EVER buy IC's :evil:
-Floopy

norm8332
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Re: Imagine if Commodore

Postby norm8332 » Mon Jan 08, 2018 1:08 pm

Floopy wrote:I only buy passive components from China. NEVER EVER buy IC's :evil:


Good advice. But if for some reason you have too (like availability), I recommend using eBay because you can file a claim if there is an issue and the buyer always wins. I once got a RIOT chip for a Atari 2600 from a Chinese seller and it was the real thing. Also got a great deal on a couple authentic VIC-1 chips (6560-101) a few months ago.

On the other hand I got a bunch of GAL20v8b chips that were clearly re-marks and some were not even from Lattice (original manufacturer), they were other brands (with different speed specs and programming voltages) re-marked to Lattice. Got my money back and kept the 50 chips. All of the Chinese-sold EPROMs are re-marks, I once ordered 27c64s and received chips marked 27c64 but they were actually the non CMOS 2764A variety. I didn't file a claim for the EPROMs because I expected re-marks at the price and they work fine.

Oh and just forget about ordering op amps from Chinese vendors I made the mistake on two occasions and both times the frequency performance of the amps was trash..worse than the ancient 1458 dual op amp no matter the markings.
Last edited by norm8332 on Mon Jan 08, 2018 3:26 pm, edited 1 time in total.

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Re: Imagine if Commodore

Postby Floopy » Mon Jan 08, 2018 1:48 pm

norm8332 wrote:Good advice. But if for some reason you have to (like availability), I recommend using eBay because you can file a claim if there is an issue and the buyer always wins. I once got a RIOT chip for a Atari 2600 from a Chinese seller and it was the real thing. Also got a great deal on a couple authentic VIC-1
Oh and just forget about ordering op amps from Chinese vendors I made the mistake on two occasions and both times the frequency performance of the amps was trash..worse than the ancient 1458 dual op amp no matter the markings.


I just want to be safe so that's why I just use Mouser and Digikey now. Sure it might be more expensive, but I get what I paid for!

"the buyer always wins" very true.
-Floopy

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Re: Imagine if Commodore

Postby eslapion » Mon Jan 08, 2018 1:52 pm

norm8332 wrote:... All of the Chinese-sold EPROMs are re-marks, I once ordered 27c64s and received chips marked 27c64 but they were actually the non CMOS 2764A variety. I didn't file a claim for the EPROMs because I expected re-marks at the price and they work fine.

That's why people ordering M27C512-90B6 ICs from eBay thinking they'll get a good way to make a cheap PLA sub actually get crap which only generates garbage.
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Re: Imagine if Commodore

Postby Floopy » Mon Jan 08, 2018 7:11 pm

The PLA is an EPROM?
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Gyro Gearloose
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Re: Imagine if Commodore

Postby Gyro Gearloose » Mon Jan 08, 2018 9:06 pm

groepaz wrote:somehow seeing ppl arguing over this trivial stuff is cute <3


If MC Scratchy is so concerned about his "paternity", he can scratch all the traces off the board, that works too.

It's just ridiculous to have that kind of attitude in such a small community. As if we don't have the combined knowledge to either make our own or trivially reverse engineer it. It's not the design for DEMO after all. https://en.wikipedia.org/wiki/DEMOnstration_Power_Station

I just find it hilarious that the VIC is the "friendly" computer with full schematics and parts published by the company and to have the Itchy & Scratchy show going on is just weird. Total douche move, IMO.

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Re: Imagine if Commodore

Postby norm8332 » Mon Jan 08, 2018 10:12 pm

Floopy wrote:The PLA is an EPROM?


The PLA is a Programmable Logic Array. It's different than an EPROM. But an EPROM can act as a PLA in some cases. It is best described here: https://en.wikipedia.org/wiki/Programmable_logic_array

Exerpt:
Advantages over read-only memory (ROM)
The desired outputs for each combination of inputs could be programmed into a read-only memory, with the inputs being loaded onto the address bus and the outputs being read out as data. However, that would require a separate memory location for every possible combination of inputs, including combinations that are never supposed to occur, and also duplicating data for "don't care" conditions (for example, logic like "if input A is 1, then, as far as output X is concerned, we don't care what input B is": in a ROM this would have to be written out twice, once for each possible value of B, and as more "don't care" inputs are added, the duplication grows exponentially); therefore, a programmable logic array can often implement a piece of logic using fewer transistors than the equivalent in read-only memory. This is particularly valuable when it is part of a processing chip where transistors are scarce (for example, the original 6502 chip contained a PLA to direct various operations of the processor[2]).


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