38 40 and the rack side panels 108 to form an h shaped space the space behind the computers may however be cordoned off to leave only a rectangular volume if desired when back connected units such as array modules 90 and computer modules 88 or 96 are used in combination in a rack 108 they are also preferably configured in this manner to define preferably with other computers of one height or another as described in the present invention such channels or spaces the back to back connection between the units will not significantly hinder the functionality provided by the air space however it is highly undesirable to have the air space cluttered by other structure such as cables cords and the like this is why the front access configurations of the inventive chassis are advantageously used in conjunction with providing an air space between computer modules within a rack 98 or other enclosure as might be used as mentioned above the space provided between computer modules may be advantageously used in a number of ways for instance as illustrated in fig5 a positive airflow as optionally indicated from above below or in both directions may be provided to the space providing a measure of gas pressure will tend to force air through vents 80 in the units defining the space as indicated if enough pressure is provided it would be possible in principle to provide computers without fans however the primary intent in providing air under pressure to the back space 106 and or side space 110 is to assist the fans or to provide a measure of.