Artifact
fc81a76931c1de0725570c9a377900215ac7876dc718641d43d6ff71501c4263:
Wiki page
[TD8E vs TC08] by
tangent
2019-02-12 05:36:57.
0000: 44 20 32 30 31 39 2d 30 32 2d 31 32 54 30 35 3a D 2019-02-12T05:
0010: 33 36 3a 35 37 2e 35 30 39 0a 4c 20 54 44 38 45 36:57.509.L TD8E
0020: 5c 73 76 73 5c 73 54 43 30 38 0a 4e 20 74 65 78 \svs\sTC08.N tex
0030: 74 2f 78 2d 6d 61 72 6b 64 6f 77 6e 0a 55 20 74 t/x-markdown.U t
0040: 61 6e 67 65 6e 74 0a 57 20 31 37 30 37 0a 54 68 angent.W 1707.Th
0050: 65 20 60 6f 73 38 2e 74 75 35 36 60 20 66 69 6c e `os8.tu56` fil
0060: 65 20 73 68 69 70 70 65 64 20 77 69 74 68 20 65 e shipped with e
0070: 61 72 6c 79 20 72 65 6c 65 61 73 65 73 20 6f 66 arly releases of
0080: 20 74 68 65 20 50 69 44 50 2d 38 2f 49 20 73 6f the PiDP-8/I so
0090: 66 74 77 61 72 65 20 77 61 73 20 61 6e 20 69 6d ftware was an im
00a0: 61 67 65 20 63 72 65 61 74 65 64 20 66 72 6f 6d age created from
00b0: 20 61 20 44 45 43 74 61 70 65 20 66 6f 75 6e 64 a DECtape found
00c0: 20 72 75 6e 6e 69 6e 67 20 6f 6e 20 73 6f 6d 65 running on some
00d0: 6f 6e 65 27 73 20 50 44 50 2d 38 20 73 79 73 74 one's PDP-8 syst
00e0: 65 6d 2e 20 54 68 61 74 20 73 79 73 74 65 6d 20 em. That system
00f0: 68 61 64 20 61 20 54 44 38 45 20 22 53 69 6d 70 had a TD8E "Simp
0100: 6c 65 20 44 45 43 74 61 70 65 22 20 63 6f 6e 74 le DECtape" cont
0110: 72 6f 6c 6c 65 72 20 74 68 61 74 20 72 65 71 75 roller that requ
0120: 69 72 65 64 20 74 68 65 20 43 50 55 20 74 6f 20 ired the CPU to
0130: 6d 6f 6e 69 74 6f 72 20 74 68 65 20 74 61 70 65 monitor the tape
0140: 20 61 73 20 69 74 20 73 70 65 64 20 70 61 73 74 as it sped past
0150: 20 74 68 65 20 68 65 61 64 73 2c 20 61 6e 64 20 the heads, and
0160: 74 72 61 6e 73 66 65 72 72 65 64 20 64 61 74 61 transferred data
0170: 20 74 68 72 6f 75 67 68 20 74 68 65 20 41 43 2c through the AC,
0180: 20 6e 6f 74 20 62 79 20 75 73 69 6e 67 20 44 69 not by using Di
0190: 72 65 63 74 20 4d 65 6d 6f 72 79 20 41 63 63 65 rect Memory Acce
01a0: 73 73 2e 0d 0a 0d 0a 4d 6f 73 74 20 73 75 72 76 ss.....Most surv
01b0: 69 76 69 6e 67 20 50 44 50 2d 38 2e 65 20 68 61 iving PDP-8.e ha
01c0: 72 64 77 61 72 65 20 68 61 73 20 74 68 61 74 20 rdware has that
01d0: 73 69 6e 67 6c 65 2d 63 61 72 64 20 44 45 43 74 single-card DECt
01e0: 61 70 65 20 63 6f 6e 74 72 6f 6c 6c 65 72 2e 20 ape controller.
01f0: 20 48 6f 77 65 76 65 72 2c 20 74 68 65 72 65 20 However, there
0200: 69 73 20 61 6e 6f 74 68 65 72 20 63 6f 6e 74 72 is another contr
0210: 6f 6c 6c 65 72 20 61 76 61 69 6c 61 62 6c 65 20 oller available
0220: 66 6f 72 20 74 68 65 20 50 44 50 2d 38 2c 20 74 for the PDP-8, t
0230: 68 65 20 54 43 30 38 20 77 68 69 63 68 20 6f 66 he TC08 which of
0240: 66 6c 6f 61 64 73 20 74 6f 20 68 61 72 64 77 61 floads to hardwa
0250: 72 65 20 6d 6f 72 65 20 6f 66 20 74 68 65 20 74 re more of the t
0260: 61 70 65 20 6d 6f 74 69 6f 6e 20 61 6e 64 20 75 ape motion and u
0270: 73 65 73 20 44 4d 41 20 74 6f 20 74 72 61 6e 73 ses DMA to trans
0280: 66 65 72 20 64 61 74 61 2e 20 42 65 66 6f 72 65 fer data. Before
0290: 20 74 68 65 20 61 64 76 65 6e 74 20 6f 66 20 74 the advent of t
02a0: 68 65 20 50 44 50 2d 38 20 4f 4d 4e 49 42 55 53 he PDP-8 OMNIBUS
02b0: 2c 20 74 68 65 20 54 43 30 38 20 77 61 73 20 74 , the TC08 was t
02c0: 68 65 20 6f 6e 6c 79 20 63 6f 6e 74 72 6f 6c 6c he only controll
02d0: 65 72 20 6f 70 74 69 6f 6e 20 61 76 61 69 6c 61 er option availa
02e0: 62 6c 65 2c 20 62 75 74 20 69 74 20 77 61 73 20 ble, but it was
02f0: 65 78 70 65 6e 73 69 76 65 2e 0d 0a 0d 0a 48 65 expensive.....He
0300: 72 65 27 73 20 77 68 65 72 65 20 74 68 65 20 69 re's where the i
0310: 6e 74 65 72 65 73 74 69 6e 67 20 74 72 61 64 65 nteresting trade
0320: 6f 66 66 20 63 6f 6d 65 73 20 69 6e 3a 20 65 6d off comes in: em
0330: 75 6c 61 74 69 6e 67 20 61 20 44 4d 41 20 64 65 ulating a DMA de
0340: 76 69 63 65 20 69 6e 20 53 49 4d 48 20 69 73 20 vice in SIMH is
0350: 71 75 69 63 6b 20 61 6e 64 20 65 61 73 79 2e 20 quick and easy.
0360: 20 59 6f 75 72 20 64 72 69 76 65 72 20 67 65 74 Your driver get
0370: 73 20 74 68 65 20 70 6f 69 6e 74 65 72 20 74 6f s the pointer to
0380: 20 74 68 65 20 62 6c 6f 63 6b 73 20 61 6e 64 20 the blocks and
0390: 63 6f 70 69 65 73 20 74 68 65 6d 2e 20 54 68 65 copies them. The
03a0: 20 54 43 30 38 20 65 6d 75 6c 61 74 6f 72 20 66 TC08 emulator f
03b0: 6f 72 20 53 49 4d 48 20 69 73 20 73 69 6d 70 6c or SIMH is simpl
03c0: 65 20 61 6e 64 20 72 75 6e 73 20 61 73 20 66 61 e and runs as fa
03d0: 73 74 20 61 73 20 61 20 62 79 74 65 20 63 6f 70 st as a byte cop
03e0: 79 2e 0d 0a 0d 0a 45 6d 75 6c 61 74 69 6e 67 20 y.....Emulating
03f0: 74 68 65 20 54 44 38 45 20 69 73 20 68 61 72 64 the TD8E is hard
0400: 65 72 2e 20 20 59 6f 75 20 6c 69 73 74 65 6e 20 er. You listen
0410: 66 6f 72 20 74 68 65 20 63 6f 6d 6d 61 6e 64 73 for the commands
0420: 20 74 6f 20 73 74 61 72 74 20 74 68 65 20 74 61 to start the ta
0430: 70 65 20 6d 6f 76 69 6e 67 2c 20 61 6e 64 20 74 pe moving, and t
0440: 68 65 6e 20 66 6f 72 20 74 68 65 20 64 65 73 69 hen for the desi
0450: 72 65 64 20 62 6c 6f 63 6b 20 6e 75 6d 62 65 72 red block number
0460: 2e 20 54 68 65 6e 20 79 6f 75 20 77 61 69 74 20 . Then you wait
0470: 66 6f 72 20 65 61 63 68 20 31 32 20 62 69 74 20 for each 12 bit
0480: 77 6f 72 64 20 74 6f 20 67 6f 20 69 6e 74 6f 20 word to go into
0490: 74 68 61 74 20 62 6c 6f 63 6b 20 74 6f 20 63 6f that block to co
04a0: 6d 65 20 74 6f 20 79 6f 75 20 74 68 72 6f 75 67 me to you throug
04b0: 68 20 74 68 65 20 65 6d 75 6c 61 74 69 6f 6e 20 h the emulation
04c0: 6f 66 20 61 20 70 72 6f 67 72 61 6d 6d 65 64 20 of a programmed
04d0: 49 2f 4f 20 69 6e 73 74 72 75 63 74 69 6f 6e 20 I/O instruction
04e0: 74 68 61 74 20 70 75 74 20 74 68 61 74 20 77 6f that put that wo
04f0: 72 64 20 69 6e 20 74 68 65 20 50 44 50 2d 38 20 rd in the PDP-8
0500: 41 43 2e 0d 0a 0d 0a 49 66 20 61 6c 6c 20 79 6f AC.....If all yo
0510: 75 20 65 76 65 72 20 77 61 6e 74 20 74 6f 20 64 u ever want to d
0520: 6f 20 69 73 20 70 6c 61 79 20 77 69 74 68 20 44 o is play with D
0530: 45 43 74 61 70 65 20 75 6e 64 65 72 20 53 49 4d ECtape under SIM
0540: 48 2c 20 5b 63 6f 6e 66 69 67 75 72 65 20 74 68 H, [configure th
0550: 65 20 50 69 44 50 2d 38 2f 49 20 73 6f 66 74 77 e PiDP-8/I softw
0560: 61 72 65 20 64 69 73 74 72 69 62 75 74 69 6f 6e are distribution
0570: 5d 28 2f 64 6f 63 2f 74 72 75 6e 6b 2f 52 45 41 ](/doc/trunk/REA
0580: 44 4d 45 2e 6d 64 5d 20 69 6e 20 74 68 65 20 64 DME.md] in the d
0590: 65 66 61 75 6c 74 20 77 61 79 2c 20 77 68 69 63 efault way, whic
05a0: 68 20 6e 6f 77 20 75 73 65 73 20 74 68 65 20 54 h now uses the T
05b0: 43 30 38 20 64 65 76 69 63 65 2e 20 28 54 68 69 C08 device. (Thi
05c0: 73 20 73 69 6e 63 65 20 72 65 6c 65 61 73 65 20 s since release
05d0: 32 30 31 39 30 32 78 78 2e 29 20 54 68 65 20 54 201902xx.) The T
05e0: 43 30 38 20 73 69 6d 75 6c 61 74 69 6f 6e 20 69 C08 simulation i
05f0: 73 20 61 20 4c 4f 54 20 66 61 73 74 65 72 2e 20 s a LOT faster.
0600: 0d 0a 0d 0a 48 6f 77 65 76 65 72 2c 20 69 66 20 ....However, if
0610: 79 6f 75 20 61 72 65 20 75 73 69 6e 67 20 53 49 you are using SI
0620: 4d 48 20 61 6e 64 20 74 68 65 20 50 69 44 50 2d MH and the PiDP-
0630: 38 2f 49 20 74 6f 20 63 72 65 61 74 65 20 54 55 8/I to create TU
0640: 35 36 20 69 6d 61 67 65 73 20 66 6f 72 20 75 73 56 images for us
0650: 65 20 6f 6e 20 72 65 61 6c 20 68 61 72 64 77 61 e on real hardwa
0660: 72 65 2c 20 79 6f 75 20 6d 61 79 20 77 61 6e 74 re, you may want
0670: 20 74 6f 20 63 6f 6e 66 69 67 75 72 65 20 69 74 to configure it
0680: 20 74 6f 20 75 73 65 20 74 68 65 20 54 44 38 45 to use the TD8E
0690: 2c 20 62 65 63 61 75 73 65 20 69 74 27 73 20 74 , because it's t
06a0: 68 65 20 6d 6f 72 65 20 63 6f 6d 6d 6f 6e 6c 79 he more commonly
06b0: 20 66 6f 75 6e 64 20 44 45 43 74 61 70 65 20 63 found DECtape c
06c0: 6f 6e 74 72 6f 6c 6c 65 72 3a 0d 0a 0d 0a 20 20 ontroller:....
06d0: 20 20 20 24 20 2e 2f 63 6f 6e 66 69 67 75 72 65 $ ./configure
06e0: 20 2d 2d 62 6f 6f 74 2d 74 61 70 65 2d 63 6f 6e --boot-tape-con
06f0: 66 69 67 3d 74 64 31 32 6b 0a 5a 20 36 34 35 65 fig=td12k.Z 645e
0700: 33 66 32 63 63 61 36 63 31 35 63 30 37 38 66 65 3f2cca6c15c078fe
0710: 65 62 65 33 61 61 34 64 63 65 64 64 0a ebe3aa4dcedd.