CCID20 CCDs are designed and produced by personnel at MIT/Lincoln Laboratory. The CCDs are thinned, back illuminated, 4096 X 2048 15-micrometer square pixel, three- side buttable devices. Some CCDs have been made on high- resistivity bulk silicon and others have been made on standard resistivity epitaxial silicon. Recently many devices from the first round of production of these CCDs have been tested at the UCO/Lick Observatory Detector Development Laboratory. In this paper we present the results of the measurements of horizontal and vertical charge transfer efficiency, low- temperature dark current, localized charge traps, full well, responsive quantum efficiency, and fringing. We present performance measurements of the on-chip amplifier including measurements of read-out noise, gain and linearity with different bias voltages. Cross-talk between the two on-chip amplifiers is discussed. High resistivity CCDs made by MIT/Lincoln show higher QE and less QE variation at long wavelengths than regular thin CCDs. However, they are subject to additional lateral charge diffusion and cosmic-ray effects. We will give a comparison between the two kinds of CCID20 CCDs. CCID20 CCDs are not MPP devices. It is much more difficult to get high full well, low spurious charge, low dark current and low residual image, simultaneously. We present optimized parallel clocks and a special erasing procedure to help solve these problems. Devices from this first round of CCID20 CCDs exhibit a rectangular pattern of QE variations caused by backside surface treatment problems.