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Re: S-100 8086 Up and Running

Hi John,

What you're saying makes great sense and I definately will cover my
EPROM windows.
Interestingly the specs for erasing an Intel 2716 and a AMD 27C512 are
the same:

"A dosage of 15 W seconds/cm2 is required to
completely erase the device. This dosage can be obtained
by exposure to an ultraviolet lamp—wavelength
of 2537 Å—with intensity of 12,000 μW/cm2 for 15 to 20
minutes. The device should be directly under and
about one inch from the source, and all filters should be
removed from the UV light source prior to erasure."

Maybe they have to increase the UV filtering property of the EPROM
windows to maintain the erasure specification if the cells are more
sensitive to UV erasure. What do you think? Sorry if this is getting
slightly off topic.


On Dec 27, 3:28 pm, "John Monahan" <mon...@vitasoft.org> wrote:
> FWIW Leon, the newer high capacity EPROMS have tiny cells and so are much
> more susceptible to UV exposure. The old 2716's etc. were hard to erase even
> with a proper UV lamp!  Remember with erasing, you move electrons into an
> isolated charged island  on a silicon insulator.  It's not an all or nothing
> effect, as the charge builds up the cells with 0's  will be unreliable at
> high speed reads.
> John
> John Monahan Ph.D
> mon...@vitasoft.org
> -----Original Message-----
> From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On
> Behalf Of Elsid
> Sent: Monday, December 26, 2011 7:58 PM
> To: N8VEM-S100
> Subject: [N8VEM-S100:587] Re: S-100 8086 Up and Runing
> Hi John, Andrew and Robert and others,
> Thanks for the good comments and tips. Yes I will cover the EPROM windows
> when I've finish reprogamming. Mind you we once put a programmed uncovered
> EPROM in the sun on a window ledge for a year just to check how sensitive it
> was - no corruption. The house window glass filters out most of the hard UV
> I think.
> Sorry about the spelling error in the subject. (Runing instead of
> running)
> I'm running a purely N8VEM S-100 system except for the 12 slot Morrow
> WonderBuss Backplane. I was using the N8VEM backplane but I now have nine
> boards in this system and N8VEM board is only 8 slots. How's that extension
> backplane coming on?
> I have the N8VEM Z80 board in the bus (buss?) and am able to swtich back and
> forth between 8086 and Z80 monitors without problem.
> I uploaded some more photos to:http://n8vem-sbc.pbworks.com/w/browse/#view=ViewFolder¶m=8086
> Unfortunately the last photo seems to upset the PBworks system and boots you
> back to the home page. I can't delete the photo to clean things up. I tried
> reloading the photo but the upload didn't progress.
> The N8VEM website seems very slow to respond at the moment.
> Have a Happy New Year
> Leon
> On Dec 27, 4:32 am, "John Monahan" <mon...@vitasoft.org> wrote:
> > Delighted to hear that Leon. Always a relief to have somebody else
> > independently get a board up and running in case I overlooked
> > something.  K8 is tricky. It decides when the pWR* & pDBIN signals
> > actually become active on the bus. According to IEEE-696 they are only
> > active AFTER pSync and pSTVAL go inactive.  You can sometimes "help"
> > I/O boards get a jump on things if you let them out earlier (K2-3) and
> > this run the bus at a slightly higher speed (or fewer wait states).
> > However some boards may not tolerate this.
> > I have not played around with higher speed chips but I suspect you
> > could squeeze 10MHz - possibly 11MHz out of the board  by playing
> > around with things.  I have currently settled to 9MHz (2 I/O wait
> > states) which is definitely stable with a 22 slot (Godboud active
> terminated motherboard).
> > Be sure to place the CPU card in the middle of the bus and the 4MG
> > Static RAM card at least 4 slots away.
> > BTW, you might want to cover the windows  on the EPROMS. UV light from
> > sunlight will eventually eat into them.
> > John
> > John Monahan Ph.D
> > mon...@vitasoft.org
> > -----Original Message-----
> > From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com]
> > On
> > Behalf Of Elsid
> > Sent: Monday, December 26, 2011 2:43 AM
> > To: N8VEM-S100
> > Subject: [N8VEM-S100:575] S-100 8086 Up and Runing
> > Hi and Seasons Greatings.
> > All the best to everyone and their families.
> > I've just completed my S-100 8086 board.
> > See photos
> > at:http://n8vem-sbc.pbworks.com/w/browse/#view=ViewFolder¶m=8086
> > Everything went smoothly except a missing K8 jumper 1-2 gave me some
> > grief for a while.
> > I have a V30 CPU and a 24MHz oscillator (8MHz clock) without any problems.
> > I'll try  10MHz next when I get a crystal.
> > Next step is to get CPM86 and MSDOS going.
> > Thanks for another great board John and Andrew.
> > Leon- Hide quoted text -
> > - Show quoted text -- Hide quoted text -
> - Show quoted text -