Xetec 32k

History and Preservation Issues

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norm8332
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Xetec 32k

Postby norm8332 » Mon Jan 23, 2017 6:54 pm

I got this as a throw-in for a messed up e-bay order (with my remaining order). I haven't seen this before. Is it rare? It does work, I just tried it with a 32k game.

P1010651.jpg
Last edited by norm8332 on Mon Jan 23, 2017 9:39 pm, edited 2 times in total.

eslapion
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Re: Xetec 32k

Postby eslapion » Mon Jan 23, 2017 8:26 pm

I don't know if it is rare but I find it very interesting. I suppose it's worth adding to the Wiki.

Can you show the board inside ?
Last edited by eslapion on Tue Jan 24, 2017 1:15 am, edited 1 time in total.
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norm8332
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Re: Xetech 32k

Postby norm8332 » Mon Jan 23, 2017 9:14 pm

eslapion wrote:I don't know if it is rare but I find it very interesting. I suppose it's worth adding to the Wiki.

Can you show the board inside ?


Sure: I carefully took it apart without damage..Its the same cart shell type as a standard Commordore with locking tabs in the rear and front with a center screw. Looks like a DRAM card with a refresh circuit.
P1010652.JPG

dragos
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Re: Xetec 32k

Postby dragos » Mon Jan 23, 2017 9:29 pm

Hmm, I sure thought I had one of those, but I guess not. let me know if you decide to sell it :)
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Re: Xetec 32k

Postby eslapion » Tue Jan 24, 2017 1:14 am

norm8332 wrote:... Looks like a DRAM card with a refresh circuit.

Looks like a card nobody is going to replicate anytime soon!!

For one thing it contains a PAL logic circuit, a PAL10L8. It also uses DRAM chips I haven't seen anywhere else ever, 32kbit chips!!
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Re: Xetec 32k

Postby CanadaPhil » Tue Jan 24, 2017 5:15 am

dragos wrote:Hmm, I sure thought I had one of those, but I guess not. let me know if you decide to sell it :)


Oh oh.... I think another $2,500 ebay listing is in the works!

:D

norm8332
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Re: Xetec 32k

Postby norm8332 » Tue Jan 24, 2017 8:37 am

CanadaPhil wrote:
dragos wrote:Hmm, I sure thought I had one of those, but I guess not. let me know if you decide to sell it :)


Oh oh.... I think another $2,500 ebay listing is in the works!

:D


I don't think so, it is just a ram expander, not a game. The other one is open to offers by the way..that price is not written in stone.

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Re: Xetec 32k

Postby eslapion » Tue Jan 24, 2017 2:20 pm

CanadaPhil wrote:
dragos wrote:Hmm, I sure thought I had one of those, but I guess not. let me know if you decide to sell it :)


Oh oh.... I think another $2,500 ebay listing is in the works!

:D

Some people may be impressed by uniqueness and looks, personally, I am always more interested in functionality. From that stand point, this Xetec expander uses 8 DRAM chips, just like a C64 and half a dozen 74LS chips so it must be a power hog which turns old 2-prong PSU VICs into a good winter home heating system.

I can make a 20 grams 32k expansion with similar functionality using a 4.5x9cm board, 2 chips and it will consume about 10mA of power - all this for about 30$US.

Guess which one is likely to last longer and have no detrimental impact on the lifespan of your dear old machine ?
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RobertBe
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Re: Xetec 32k

Postby RobertBe » Wed Jan 25, 2017 12:42 am

eslapion wrote:...so it must be a power hog which turns old 2-prong PSU VICs into a good winter home heating system.

Then you'll have to buy the new Ray Carlsen 2-prong power supply that outputs 9VAC at 3 amps. :)

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Re: Xetec 32k

Postby eslapion » Wed Jan 25, 2017 2:47 am

RobertBe wrote:
eslapion wrote:...so it must be a power hog which turns old 2-prong PSU VICs into a good winter home heating system.

Then you'll have to buy the new Ray Carlsen 2-prong power supply that outputs 9VAC at 3 amps. :)

Not going to change anything for the 5V regulator which is internal on these VIC-20s - for every single watt of power they provide to the rest of the computer, they dissipate 800mW of heat.
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RobertBe
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Re: Xetec 32k

Postby RobertBe » Wed Jan 25, 2017 3:34 am

Then it's time for less power hungry R65C02 and 65C22 chips.

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eslapion
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Re: Xetec 32k

Postby eslapion » Wed Jan 25, 2017 6:02 am

RobertBe wrote:Then it's time for less power hungry R65C02 and 65C22 chips.

Personally, I don't think I would ever replace the original 1981 6502 and 6522s of my PET style keyboard VIC-20 with CMOS versions because I use a 32k RAM expansion that guzzles up power and makes the regulator overheat.

I strongly feel I'd rather go the other way around and use a RAM expansion with modern parts that uses only a trickle of power...
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Re: Xetec 32k

Postby norm8332 » Wed Jan 25, 2017 5:38 pm

you guys are going overboard. It doesn't draw much. It doesn't heat up the regulator. It draws 100-150 ma max. We are talking about 8 32Kx1 DRAM chips here and a few LS logic chips. Each DRAM chip draws 50ma max when refreshed in a sequential refresh. And the logic draws about 50-100ma when performing an operation. If you are trying to push your RAM expansion, while i'm sure its very power efficient, please do it in another thread. :mrgreen:

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Re: Xetec 32k

Postby eslapion » Wed Jan 25, 2017 9:59 pm

norm8332 wrote:It doesn't draw much. It doesn't heat up the regulator. It draws 100-150 ma max.

That's a huge amount of power for the 2-Prong PSU VIC-20. It's about the same as is used by the Protecto-80. The 5V regulator already dissipates about 4W of heat when nothing is attached, a 150mA load on the cart port is 750mW of power and this will increase the regulator dissipated heat by 600mW.

The total dissipated heat will rise from 9W (regulator and computer) to 10.35W (computer, regulator and RAM cartridge).

As I said, the ultimate expander I used to sell would draw about 10mA of power if it had only RAM (32k, just like the Xetec). It would rise to about 20mA if you added an EPROM.

The reason why the C64 board 250466 consumes so much less power compared to previous C64 boards is mainly because it uses 2 64kx4 DRAM chips instead of 8 64kx1 chips.

Of course, if you have a VIC with a round power connector and use a C64 power supply, the impact will be negligible.
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Re: Xetec 32k

Postby norm8332 » Thu Jan 26, 2017 12:03 am

eslapion wrote:
norm8332 wrote:It doesn't draw much. It doesn't heat up the regulator. It draws 100-150 ma max.

That's a huge amount of power for the 2-Prong PSU VIC-20. It's about the same as is used by the Protecto-80. The 5V regulator already dissipates about 4W of heat when nothing is attached, a 150mA load on the cart port is 750mW of power and this will increase the regulator dissipated heat by 600mW.

The total dissipated heat will rise from 9W (regulator and computer) to 10.35W (computer, regulator and RAM cartridge).

As I said, the ultimate expander I used to sell would draw about 10mA of power if it had only RAM (32k, just like the Xetec). It would rise to about 20mA if you added an EPROM.

The reason why the C64 board 250466 consumes so much less power compared to previous C64 boards is mainly because it uses 2 64kx4 DRAM chips instead of 8 64kx1 chips.

Of course, if you have a VIC with a round power connector and use a C64 power supply, the impact will be negligible.


A lot of what you said depends on the input voltage. Two prong Vic-20 were supplied with power supplies that ranged from 9V to 11V AC. The lower input voltage with a 9V supply will allow the regulator to run cooler with higher efficiency. Or you could do what I do and supply a regulated 9.75VDC Using a buck converter and a 12V switching supply. This supplies the regulator with about 7.5V After the full bridge voltage drop. This is only 0.8V above the dropout voltage of the regulator and allows you to get up to 85% efficiency from it. It runs barely warm with this setup.

But I do get your point. someone running 10-11VAC will already have a baking Vic and additional draw will just make it worse. After rectification 11VAC will be close to 14 VDC at the regulator.


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