I've played with ccache.

	A	B
hostname	t-106	z87
cpu	AMD Opteron	Core i7
core	x 4	x 4
cpu type	1352	4770
clock	2.1GHz	3.40GHz
Phy.Mem	8GB	8GB
NetBSD	i386	amd64
Release	7.99.1	6.1_STABLE
WRKOBJDIR	hard disk	tmpfs

1. B with no ccache

       average             total
       383 sec 6'23        140'35
   

2. B with ccache on hard disk

       about twice elapse time
       Overhead of R/W on ccache costs too much.
   

3. B with ccache on tmpfs

       about the same as (1)
       Probably other than file I/O is bottle neck.
   

4. A without ccache See below
5. A with ccache on tmpfs. See below

For the case 4 and 5, those are shown in the graph above (Vertical axis is seconds to package, click to get large graph)
ccache size for gnuradio is 200-300MB.

(4) A without ccache
                       package    sec ->  m  s (      size)       gunzip 
            gnuradio-3.7.5.tgz    588     9'48 (      1431)        10240
        gnuradio-fec-3.7.5.tgz   1629    27'09 (    531528)      3348480
       gnuradio-noaa-3.7.5.tgz   1904    31'44 (    143435)       778240
    gnuradio-doxygen-3.7.5.tgz   2041    34'01 ( 165460182)    367390720
   gnuradio-channels-3.7.5.tgz   2048    34'08 (    283080)      1689600
      gnuradio-wxgui-3.7.5.tgz   2089    34'49 (    426312)      2140160
      gnuradio-pager-3.7.5.tgz   2207    36'47 (    166597)       839680
        gnuradio-uhd-3.7.5.tgz   2589    43'09 (    692416)      3348480
      gnuradio-qtgui-3.7.5.tgz   2677    44'37 (   1035591)      5908480
      gnuradio-utils-3.7.5.tgz   2824    47'04 (    210593)      1443840
    gnuradio-wavelet-3.7.5.tgz   2925    48'45 (    135809)       634880
        gnuradio-fcd-3.7.5.tgz   2961    49'21 (    149196)       552960
  gnuradio-video-sdl-3.7.5.tgz   2993    49'53 (    117356)       512000
    gnuradio-digital-3.7.5.tgz   3023    50'23 (   1937120)     13527040
       gnuradio-core-3.7.5.tgz   3106    51'46 (   9178054)     60876800
        gnuradio-dtv-3.7.5.tgz   3118    51'58 (    278592)      1566720
       gnuradio-atsc-3.7.5.tgz   3146    52'26 (    426333)      2754560
  gnuradio-companion-3.7.5.tgz   3306    55'06 (    234340)      1536000
     gnuradio-zeromq-3.7.5.tgz   3415    56'55 (    195177)      1136640
    gnuradio-vocoder-3.7.5.tgz   3495    58'15 (    560207)      2928640
   gnuradio-ctrlport-3.7.5.tgz   3898    64'58 (     24891)       143360
    gnuradio-trellis-3.7.5.tgz   4011    66'51 (   1417666)     11386880
                         Total  59993   999'53 ( 183605906)    484454400 22 files
    gnuradio-default-3.7.5.tgz   3458    57'38 ( 203129175)    529397760

------------------------------------
(5) A with ccache on tmpfs.
                       package    sec ->  m  s (      size)       gunzip 
            gnuradio-3.7.5.tgz    584     9'44 (      1432)        10240
       gnuradio-core-3.7.5.tgz   1377    22'57 (   9178123)     60876800
        gnuradio-dtv-3.7.5.tgz   1442    24'02 (    278601)      1566720
   gnuradio-channels-3.7.5.tgz   1453    24'13 (    283090)      1689600
      gnuradio-pager-3.7.5.tgz   1456    24'16 (    166597)       839680
       gnuradio-noaa-3.7.5.tgz   1464    24'24 (    143436)       778240
    gnuradio-wavelet-3.7.5.tgz   1475    24'35 (    135819)       634880
     gnuradio-zeromq-3.7.5.tgz   1501    25'01 (    195183)      1136640
        gnuradio-fec-3.7.5.tgz   1519    25'19 (    531548)      3348480
       gnuradio-atsc-3.7.5.tgz   1535    25'35 (    426344)      2754560
      gnuradio-utils-3.7.5.tgz   1537    25'37 (    210638)      1443840
      gnuradio-qtgui-3.7.5.tgz   1546    25'46 (   1035550)      5908480
      gnuradio-wxgui-3.7.5.tgz   1560    26'00 (    426223)      2140160
  gnuradio-video-sdl-3.7.5.tgz   1564    26'04 (    117360)       512000
   gnuradio-ctrlport-3.7.5.tgz   1591    26'31 (     24898)       143360
        gnuradio-uhd-3.7.5.tgz   1600    26'40 (    692420)      3348480
    gnuradio-vocoder-3.7.5.tgz   1616    26'56 (    560223)      2928640
        gnuradio-fcd-3.7.5.tgz   1619    26'59 (    149201)       552960
    gnuradio-digital-3.7.5.tgz   1699    28'19 (   1937131)     13527040
    gnuradio-doxygen-3.7.5.tgz   1831    30'31 ( 165464005)    367400960
    gnuradio-trellis-3.7.5.tgz   1991    33'11 (   1417653)     11386880
  gnuradio-companion-3.7.5.tgz   2509    41'49 (    234497)      1536000
                         Total  34469   574'29 ( 183609972)    484464640 22 files
    gnuradio-default-3.7.5.tgz   3227    53'47 ( 203135025)    529397760