zeddy with printed eprom

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msknight
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zeddy with printed eprom

Post by msknight »

I'm going to conclude that this was manufactured this way, as what appears to be a 649 bios is printed up on an issue 3 board ?
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1024MAK
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Re: zeddy with printed eprom

Post by 1024MAK »

Yes, we think the factory used EPROMs (as shown in the photo) when mask ROMs were not available. The chip manufacturer (Texas Instruments) offered a bulk EPROM programming service, hence the chip markings including the text "ZX81". The 64K is referring to 64K bits (which is 8K bytes).

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Lardo Boffin
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Re: zeddy with printed eprom

Post by Lardo Boffin »

I have one like that but it doesn’t work. However I liked the look of it so I put it in a display case…
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ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
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Spectrum 16k (iss 1 s/n 862)
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msknight
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Re: zeddy with printed eprom

Post by msknight »

Lardo Boffin wrote: ↑Wed Feb 07, 2024 9:56 pm I have one like that but it doesn’t work. However I liked the look of it so I put it in a display case…
I can understand that....
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