Ever seen a Cromemco Cyclops in the wild?

William Sudbrink wh.sudbrink at verizon.net
Wed Jun 10 11:49:16 CDT 2020

The really interesting thing (to me anyway) is just how

it works.  The cells are 3T1C (3 transistor, 1 capacitor).

There’s a good diagram here:




I assumed that the photons were just allowing charge to

escape across the capacitor.  Terry corrected me.  The

transistor labeled “T2” in the above diagram is what is

light sensitive.  When struck by photons, T2 allows charge

to leak to ground, discharging the cap and “flipping” the

bit to zero.




From: Eric Smith [mailto:spacewar at gmail.com] 
Sent: Wednesday, June 10, 2020 12:38 PM
To: William Sudbrink; General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Ever seen a Cromemco Cyclops in the wild?


On Tue, Jun 9, 2020 at 6:14 PM William Sudbrink <wh.sudbrink at verizon.net> wrote:

No, I'm afraid not.  I can tell you from both personal experience and from the
designer (Terry Walker) that the chip is either a Mostek MK4008P-9 or an AMI
S4008-9.  I have used both chips.  See my web page:



You obviously must be correct, and use of a DRAM makes much more sense than an SRAM. It's possible that an SRAM could be made to work as an image sensor, but it would not be anywhere near as sensitive as a DRAM. When, back in 1975, I compared the pinout to the data books I had on hand, and observed that it exactly matched the 2102, and didn't search any further. I had no idea that the MK4006 and MK4008 dynamic RAMs happen to have the same pinout as the 2102 static RAM.  Intel's own 1K DRAMs (1103 PMOS, 2105 NMOS) do not share that pinout.


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