  We exmaine the distribution of hot gas in a standard CDM model of the
universe using high resolution hydrodynamic simulations. Adopting standard
parameters determined from COBE and light element nucleosynthesis,
$\sigma_8=1.05$, $\Omega_b=0.06$ and assuming $h=0.5$, we find the X-ray
emitting clusters, compute the luminosity function at several wavelengths, the
temperature distribution and estimated sizes as well as the evolution of these
quantities with redshift. This standard CDM model, normalized to COBE, produces
approximately 5 times too much emission from clusters having
$L_x>10^{43}$erg/s, a not unexpected result. If all other parameters were
unchanged, we would expect adequate agreement for $\sigma_8=0.6$. This provides
a new and independent argument for lower small scale power than standard CDM at
the $8h^{-1}$Mpc scale. The background radiation field at 1keV due to clusters
in this model is approximately $1/3$ of the observed background which, after
correction for numerical effects, again indicates approximately 5 times too
much emission and the appropriateness of $\sigma_8=0.6$. If we had used the
observed ratio of gas to total mass in clusters, rather than basing the mean
density on light element nucleosynthesis, then the computed luminosity of each
cluster would have increased still further, by a factor of approximately ten.
Examining the ratio of gas to total mass in the clusters (which we find to be
anti-biased by a factor of approximately 0.6), normalized to $\Omega_b
h^2=0.015$, and comparing to observations, we conclude, in agreement with S.
White, that the cluster observations argue for an open universe.
