HP Forum Archive 15

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Modified HP71B Message #1 Posted by Rick Meyerson on 21 Nov 2005, 4:23 p.m. Hello: I havbe the modified HP71B with full RAM and 4X speed modifications. Would like to speak to others with this never-released unit. Rick

Re: Modified HP71B Message #2 Posted by inaki on 21 Nov 2005, 5:17 p.m., in response to message #1 by Rick Meyerson Any link to get more information on this project ? Quote: Hello: I havbe the modified HP71B with full RAM and 4X speed modifications. Would like to speak to others with this never-released unit. Rick

Re: Modified HP71B Message #3 Posted by Eric Smith on 21 Nov 2005, 6:02 p.m., in response to message #1 by Rick Meyerson Those are aftermarket modfications. There were several people and companies offering such mods commercially, and some 71B owners did the mods themselves. The speedup is just the typical capacitor value change. The memory upgrade consists of breaking open memory modules (either HP 4KB modules or CMT 32KB or 64KB modules), and wiring the circut boards into the internal chain.

Re: Modified HP71B Message #4 Posted by Howard Owen on 21 Nov 2005, 7:12 p.m., in response to message #1 by Rick Meyerson So what does "full" memory mean? The Saturn could directly address 512 KB, I believe, at least in the HP48 vintage.

Re: Modified HP71B Message #5 Posted by J-F Garnier on 24 Nov 2005, 7:42 a.m., in response to message #4 by Howard Owen The maximum theorical RAM is 384k (not including the 1.5k RAM in display ICs), starting from 30000h to EFFFFh. The area F0000-FFFFF is reserved. Due to the built-in 16k, the maximum practical value is "only" 372k. It could be achieved with a HHP 160k module in card reader, plus 3 CMT 64k front port modules, plus one HP 4k module, without HP-IL. With HP-IL and without the 4k module, we could get 368k. I never reached this amount of memory on my regular HP-71B, but easily got 320k in Emu71. Rick, What is your configuration? J-F

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