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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 20th Dec 2018, 10:13 am   #141
SiriusHardware
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Default Re: MK14 schematic revisions

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Originally Posted by Slothie View Post
My concern other than availability would be that the BPROMs may not be fast enough when its access time is added to that of the RAM and Monitor ROM, but that would be something that would be easy enough to try out, and would make fully expanding the MK14 to 512b prom + 3k RAM possible, and would make many more complex VDU projects feasable (Like MK14 space invaders ??!!)
Don't get too ambitious, the dot resolution of the VDU in graphics mode is not terribly high. 'Pong' might be a more realistic aim.

BPROMs were used on the Nascoms, or at least one of them, as custom address decoders. They are actually surprisingly fast in terms of access speed - for that reason they were often used in things like video test pattern generators where the access speed of contemporary EPROMs might have been too slow.

However, as with all things that age they are becoming more expensive and difficult to get. GALs would be another option but only a small percentage of people have programmers capable of programming them. The parts would really need to be as ubiquitous as possible. A 'modern' fast EPROM might work just as well as an address decoder but it would come in a wide bodied footprint.
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Old 20th Dec 2018, 1:00 pm   #142
Slothie
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Default Re: MK14 schematic revisions

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Originally Posted by SiriusHardware View Post
However, as with all things that age they are becoming more expensive and difficult to get. GALs would be another option but only a small percentage of people have programmers capable of programming them. The parts would really need to be as ubiquitous as possible. A 'modern' fast EPROM might work just as well as an address decoder but it would come in a wide bodied footprint.

GALs might be an option; my cheap 50 TL866CS/Minipro programmer will do Lattice GAL16V* and GAL20V* and Minipro works great on Linux under Wine with a modified DLL. Although obsolete too they seem to be far more available than BPROMS. Although I've never used GALs I have used CPLDs which are much the same. I'd have to find some logic compiler to generate the bitmap that the Minipro expects but I'm sure there's something out there for free. (Sadly the TL866 doesn't do BPROMS )

That said, if someones kitted themselves out with a programmer for Tesla PROMS for the monitor then programming an address decode PROM wont be an issue! eBay seems to be flooded with Tesla 74S571s at the moment, so perhaps I should get my act together and start looking at programming them!
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Old 20th Dec 2018, 1:02 pm   #143
SiriusHardware
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Default Re: MK14 schematic revisions

.... nudge.
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