Simple SQL too slow

Hi List,

I have a Server where a simple SQL is taking a long time to return the
results the Server settings are as follows:

Debian GNU/Linux 7 (wheezy)
CPU: Intel(R) Xeon(R) CPU E5405 @ 2.00GHz
Mem: 16GB
HD: SSG 120 GB
Postgresql 9.2

postgresql.conf
shared_buffers = 1536MB
work_mem = 32MB
maintenance_work_mem = 960MB
effective_cache_size = 4864MB

I did a test with the following SQL:

select * from MINHATABELA

It took 7 minutes to return the result.

I did the same test on a Server:

Windows Server 2012 Standard
CPU: Intel(R) Xeon(R) CPU E5-2450 @ 2.10GHz
Mem: 24GB
HD: HD 500 GB
Postgresql 9.2

postgresql.conf Default settings that come with the installation

The same SQL returned in 3 minutes.

The test in both Servers were done bench.

This table has 1888240 records whose size is 458 MB

I believe that in both Servers the response time of this SQL is very high,
but the main thing in LINUX Server has something very wrong, I think it is
something in the settings.

What can I be checking?

--
Atenciosamente
Daviramos Roussenq Fortunato