TrumpCard modification

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janbredenbeek
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Re: TrumpCard modification

Post by janbredenbeek »

XorA wrote:
janbredenbeek wrote:
XorA wrote: 256K x 4 bit is 1 megabit so its talking about the TC2
Yes, but the RAM chips are really 4 bit ones. There's a circuit diagram in the same directory (http://gigant.chem.elte.hu/ZXSpectrum/QL_Trump_Card/) where the picture resides and that clearly shows each chip has 4 data lines.
That still makes 1 megabit, so I am a little confused what you mean!
Yes the capacity is 1 Mbit, but unlike 'true' 1 Mbit chips they can store and output 4 bits at once. Which is probably the reason why the Trump Card 2 was faster - there are less refresh cycles needed during which the 68008 has to wait for RAM access.

Jan.


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Cristian
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Re: TrumpCard modification

Post by Cristian »

XorA wrote: You have the original! (of which there maybe minor revs but one of the experts will have to comment on that).
OK thanks for your clarifications :)
So there are 2 main kinds of TrumpCards: the "normal" ones (before TrumpCard2) and the TC2s.
The cards before TC2 are not all perfectly identical since underwent some revisions.
Let's hope some of the expert could notice if in this case some revision is recommended or not


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1024MAK
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Re: TrumpCard modification

Post by 1024MAK »

janbredenbeek wrote:
XorA wrote:
janbredenbeek wrote: Yes, but the RAM chips are really 4 bit ones. There's a circuit diagram in the same directory (http://gigant.chem.elte.hu/ZXSpectrum/QL_Trump_Card/) where the picture resides and that clearly shows each chip has 4 data lines.
That still makes 1 megabit, so I am a little confused what you mean!
Yes the capacity is 1 Mbit, but unlike 'true' 1 Mbit chips they can store and output 4 bits at once. Which is probably the reason why the Trump Card 2 was faster - there are less refresh cycles needed during which the 68008 has to wait for RAM access.

Jan.
Semiconductor manufacturers often use the total storage capacity of a RAM chip when talking about it in their data books and data sheets. So I expect they do the same in any promotional material.

They are true 1 M bit chips. They just have a different matrix arrangement. The CPU does not know, or care about the internal organisation of the memory chips. The refresh requirements don't depend on the chips data width. Over the years, various internal DRAM matrix arrangements have been used. Generally it's most or all of the multiplexed address row accessed by /RAS that does the refresh. But more modern chips do have the advantage of having internal "hidden" refresh. This not only makes the circuit and board design far less complex and is easier to design, but with most designs the CPU does not have to wait during a refresh. Because there is no external refresh address to the chip. The chip does the refresh during the time that it is not reading or writing data from the memory cells (it may or may not be able to put data on the bus during this time).

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1024MAK
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Re: TrumpCard modification

Post by 1024MAK »

Cristian wrote:The cards before TC2 are not all perfectly identical since underwent some revisions.
Let's hope some of the expert could notice if in this case some revision is recommended or not
I don't know what, if any revisions occurred. But the main way of reducing power usage and therefore power dissipation, is either replace bipolar and / or NMOS semiconductor chips with CMOS equivalents, or change the voltage regulator circuitry. Either replace the 7805 with a modern switching type, run the card from another off card +5V so the on-board regulator is no longer needed, or use a by-pass resistor, reducing the heat level in the regulator at the expense of heat output from the resistor (this offers absolutely no improvement in overall efficiency).

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:!: Standby alert :!:
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer in Somerset later in the year :)

QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)
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Re: TrumpCard modification

Post by XorA »

I must say with the big chunk of metal that is missing in all the pics so far as a heat sink my trump card doesn't seem to get more than luke warm! Certainly well below the worry limit for 7805!


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Re: TrumpCard modification

Post by Cristian »

XorA wrote:I must say with the big chunk of metal that is missing in all the pics so far as a heat sink my trump card doesn't seem to get more than luke warm! Certainly well below the worry limit for 7805!
I agree, and fortunately I do have the huuuuuge heatsink-cover :-)
Anyway, there still exist the power consumption and stability aspect. I'm not a big expert but, if I remember some physics principles, I think that all that heat (especially from the 7805 above MDVs) must waste a lot of power.


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1024MAK
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Re: TrumpCard modification

Post by 1024MAK »

Yep, series pass regulators like the 7805, 7809, 7812, 7905, 7912 etc will waste power. At any given current within their operating range, the power dissipated as heat is appropriately the difference between the input and output voltages multiplied by the current.

But in the 1980's and early 1990's, for relatively low power devices, this was the easiest and cheapest way of building a power supply that had the regulation required for 5V logic systems.

Now more efficient switch mode power supply units (SMPSU) are cheaper and more easily available.

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Re: TrumpCard modification

Post by Cristian »

1024MAK wrote: Now more efficient switch mode power supply units (SMPSU) are cheaper and more easily available.
Is TSR 1-2450 the only best solution or do you know other similar alternatives?


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1024MAK
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Re: TrumpCard modification

Post by 1024MAK »

There are various switching regulator replacements, in various ratings...

Here in this thread are two different ones used on ZX81 boards: Pictures of my ZX81 fitted with a RECOM 5V Regulator

Mark


:!: Standby alert :!:
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer in Somerset later in the year :)

QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)
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