QL memory expansion

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Dave
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Re: QL memory expansion

Post by Dave »

That is absolutely correct.

-80 or -100 components would be ideal. Faster chips are, in fact, more of a problem than slower chips - don't go faster than -70 and -55 would be very problematic. This is because of the noise caused by the fast rise and fall times of the faster components.


Wimdev
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Re: QL memory expansion

Post by Wimdev »

Alright, I'll give it a try. I found some -08's on eBay.

Wim


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vanpeebles
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Re: QL memory expansion

Post by vanpeebles »

Most interesting! How much would it bump the speed of a trump card by changing the chips? Are any other changes needed?


Wimdev
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Re: QL memory expansion

Post by Wimdev »

As soon as I get the faster chips, I'll post a comparison. Hopefully early next week.

Wim


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Re: QL memory expansion

Post by Wimdev »

Well, I received the -08 chips today. Eagerly swapped the 150ns versions for the speedy 80ns ones. Plugged the expanderam back into the QL, booted, and ran the ram speed test. It took exactly the same amount of time (22.5 seconds) to finish as before! Bummer. I guess there's something else that's holding it back.

Any thoughts?

Wim


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1024MAK
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Re: QL memory expansion

Post by 1024MAK »

The timing is not set by the DRAM chips, they just limit the response time that will work reliably.

Without looking at the schematic, I believe the circuit you need to adjust is whatever controls the timing of the DTACK signal.

Mark


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Dave
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Re: QL memory expansion

Post by Dave »

Don't worry. SuperRAM will show up soonish. :)

Also, endless supplies of new 40LF220s.


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1024MAK
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Re: QL memory expansion

Post by 1024MAK »

I wrote:The timing is not set by the DRAM chips, they just limit the response time that will work reliably.

Without looking at the schematic, I believe the circuit you need to adjust is whatever controls the timing of the DTACK signal.
I've had a quick look at the schematic and there are at least three, maybe four resistor/capacitor timing circuits that may need changing. Without having a working board and some suitable test gear (4 channel 'scope at least), it's not possible to work out which components need replacing, or what values the new parts should be. Sorry.

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)
Wimdev
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Re: QL memory expansion

Post by Wimdev »

Oh well. Thanks for checking though. I guess we have to wait for some new hardware developments - superram comes to mind.

Wim


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