The PIC14 seems to be a popular build once again, as genuine SC/MP chips become harder to find. Here's Karens original from 2007 as a reminder:
http://techlib.com/area_50/Readers/Karen/micro.htm#PIC14 . There are several PCB designs on the net for new builders.
As originally published, only manually keyed in programs were kept non-volatile. If you hex-loaded a program, it disappeared with the power off.
This simple edit saves manually-keyed and hex-loaded programs with the power off. Its on the "Karen Orton 'PICL' NIBL Computer & PIC14 files"
page of
http://philg.uk right at the bottom of the page.
Also when a new PIC is programmed for the very first time, ie nothing has yet been manually keyed in or hex-loaded, rather than leaving it empty,
the non-volatile ram now defaults to the Science of Cambridge Message demo from the MK14 manual.
This is overwritten as soon as any new program is keyed in or hexloaded. So you can blow a brand-new pic, plug it in, press the "SC/MP Reset" button, and type
F 2 0 and
Go, confirming that indeed "
as you can see the S of C is a jolly fine buy"
Cheers
Phil