Today's Fun plus a question

["Richard A. Cini" <rc...@optonline.net>]

Title: Today's Fun plus a question

All:

    Two quick updates and then a question...

    First, I put an ammeter on my N8VEM board stack (CPU, Disk, ECB) to see how much current is being drawn. At idle, with an IDE->CF hard drive, I get a current draw of about 1.1A on the 5v line. I didn’t have my terminal on, so I don’t know what it might be while running a sieve, but even if it’s 1.3A, that’s not so much. This at least gives me an idea about what kind of battery one might need for running it “portable”. 

    I have to do some research, but I’m thinking a LiPo battery from the model plane hobby — they’re very powerful and light-weight. Then all that’s needed is a small high-current 5v switching regulator. Chargers are more expensive, though. The typical configuration is 11.1v @ somewhere between 2200mAh – 2800mAh. I don’t know if two hours (or less) of run-time is enough for the cost and effort, however. 

    SLA batteries have higher capacities, but are way heavier.

    NiMH remote control car packs have a good power density and the chargers are less expensive, but they’re still heavy (but lighter than SLA). I’ve looked at some 9.6v NiMH packs that have 4000mAh capacities. Call that 3.5 hours (or less) of run-time. Better but not great.

    Again, I’m assuming a perfect world on the run-time. R/C car batteries are usually high-discharge-rate packs, which should work for this application.

    Second, I found a patch for CP/M in the CP/M User’s Group archive #78 which prints the user area as part of the CCP prompt (“A0>”). There appears to be enough room for this patch after the wireless code and before the end of CP/M ($F2FE I think). I haven’t burned a new ROM yet, but I’ve read that this was a common patch for people to make.

    A question regarding the battery backed RAM daughterboard -- did anyone ever have PCBs manufactured? I saw a JPG of the layout but I don’t remember seeing how this side project concluded.

    Thanks!

Rich

--
Rich Cini
Collector of Classic Computers
Build Master and lead engineer, Altair32 Emulator
http://www.altair32.com
http://www.classiccmp.org/cini