Hello Charles ! 

***WARNING: LONG MESSAGE COMING AHEAD***
Stop by, get some cigarettes -if any- , coffee or coke and a sandwich.

Nice to hear (read) from you again.

Yes - indeed IBM has a minotaur-style labyrinthic Model-numbering.

Shall I try to bring some light into this desaster ? 
Were probably a good idea for a new page ...!

I guess I should try. (Hehe !)

Okay - the IBM modelnumbers have 7 digits - as their Part-Numbers have too. Strange.
The Format is FFMM-ABC

The FF is the family-number - still numeric. FF can be

21 = Entry Line / Aptiva / PS-Note
25 = ThinkPad (early models)
26 = ThinkPad (early models)
31 = System /370, /390, 3270-Host
32 = System /370, /390, 3270-Host
33 = Optical Storage
35 = Storage Subsystems
38 = System /34, /36, /38 or AS/400 equipment
40 = InfoWindow products
41 = misc.
42 = Printer, mainly ProPrinter family
44 = Tempest (Governmental / Security)
47 = 4700 Banking Systems
48 = PC jr. products
49 = Series /1 PCs
50 = CAD-equipment / tablets / lightpen
51 = PC, XT, AT
52 = 3270-Products (PC, Printer, Display)
53 = 3270-Products (PC, Printer, Display)
55 = XTC Industrial / local Japan PC
58 = Communication Eq. / modems
60 = PowerPC
61 = RT-PC series / tapes / plotters / small systems
62 = PC-300GL Series
63 = PS-Value Point 1 & 2
64 = PS-Value Point III
65 = PC-300 Series
68 = PC-700 Series
72 = cannot remember
73 = Color Plotter
75 = Industrial PC
81 = 8100-Equipment (Banking-Loop)
82 = Networking Equipment
85 = Personal System /2
86 = PC-Server Group
93 = Rackmounted Equipment
95 = PS-Premium Line

The MM is the 'real' Model-Number - also still numeric. Too much to list.

The PS/2 -the machines of our interest- often had a 'Marketing Name'
and a Model/Type name as well:

P70   = IBM PS/2 Portable 8573-xxx
P75   = IBM PS/2 Advanced Portable 8573-4xx
55SX  = IBM PS/2 8555
L40SX = IBM PS/2 Portable 8543
N33SX = IBM PS/2 Notebook 8533
CL57  = IBM PS/2 Color Notebook 8554
Server 500      = IBM PS/2 Server 8640
ThinkPad TP710T = IBM 2523
PC-330          = IBM Desktop-PC 6576

... and so on.



Then come the Type- and Equipment code -ABC. 3 alphanumeric digits.
In the beginning the IBM gave out any number in the order of developement.

The AT 5170 for example had the models

- 068     "AT-01" 1 DD, 0 HD --/--MB, 80286-6, 256K
- 099     "AT-01" 1 DD, 1 HD 20MB,    80286-6, 256K
- 239     "AT-02" 1 DD, 1 HD 20MB,    80286-6, 512K
- 319/339 "AT-03" 1 DD, 1 HD 20/30MB, 80286-8, 512K

After a while IBM decided that it were a good idea to give infos about the machine
in this 3-digit typecode.

-ABC

-AB  = Size of Harddisk in MB without last digit
   C = Number of diskdrives

For example:

8530-002 = Mod. 30, 2 diskdrives, no harddisk
8555-061 = Mod. 55, 1 diskdrive, 60MB harddisk
8580-111 = Mod. 80, 1 diskdrive, 111 MB harddisk
8570-A21 = Mod. 70, 1 diskdrive, 120 MB harddisk ... wait a moment !

Yes: after some time this doesn't work anymore.
There were so many models with different cpu's and harddisks out.
For a while this scheme was repeated with i.e.:

8570-061 = Mod. 70, 386-16MHz, 1 DD,  60MB HD
8570-F61 = Mod. 70, 386-20MHz, 1 DD,  60MB HD
8570-121 = Mod. 70, 386-20MHz, 1 DD, 120MB HD
8570-A21 = Mod. 70, 386-25MHz, 1 DD, 120MB HD
8570-A16 = Mod. 70, 386-25MHz, 1 DD, 160MB HD ... err ?! Correct !
8570-R21 = Mod. 70, 486-25MHz, 1 DD, 120MB HD
8570-R16 = Mod. 70, 486-25MHz, 1 DD, 160MB HD ... uh - again !

8555-LT0 = Mod. 55, 386SX-16, 2MB, 1DD, no HD, TR-Adapter installed (Argh !)
8555-LE0 = Mod. 55, 386SX-16, 2MB, 1DD, no HD, Ethernet Adapter (Eck !)

Not to forget:

8555-XT0 = Mod. 55, 386SX-16, 2MB, no DD, no HD, Token-Ring (aaaahahaha !)

-The famous 'Medialess Workstation'- 
Servicing one causes nervous breakdowns.

More oddities:

Model 90 / 95 numbering

-ABC
 0   = Standard / 8MB
 A   = nationalized Version / 16MB
 V01 = Server / 16MB / 800 MB HD
  G  = 486SX-20
  H  = 486SX-20 expandable
  J  = 486SX-25
  K  = 486DX-33
  L  = 486DX/2-33/66
  M  = 486DX-50
   9 = 160MB HD
   D = 320MB HD
   F = 400MB HD
   T = 1GB HD

You feel somewhat gooey ? Me too. And I had to deal with that stuff.

It was a bad situation. 
IBM decided later to assume that a diskdrive is installed and
changed the first digit to be memory- and OS-dependent, changed the 
whole naming system and take the last digit from the Model-Family to
give details. The first Value-Points had the advantage:

638x=ValuePoint - where x is
1 = /Si energy-saver model
2 = 3 x 3 Desktop (3 slots, 3 bays)
4 = 5 x 5 Desktop (5 slots, 5 bays)
7 = 8 x 7 Minitower (8 slots, 7 bays)

The Type-digits give the Processor, the memory and the HD-capacity ..... Guess I'll stop here.


Now ... if you're not feeling too bad, let's talk a bit about Token-Ring.
The bad news at first: You need a sort of 'Hub'.
In IBM Technoslovakian this thing is called 'Multi-Access Unit' (MAU).
The most common number is 8228-001. This is a plain old passive unit which needs no AC-power.
Many companies throw these units out now, because they are not 'manageable' over software-tools.
The newer active MAUs, like 8230 are manageable - so the old 8228s have to go.

That's a 8-port unit with IBM data-connector, 1 Ring-In and 1 Ring-Out to cascade 
several MAUs up to the maximum of 240 stations per segment.
There are some compatibles on the market, ie. from AMP, which have 2, 4, 8 or even 16 ports,
RJ45-models are available too.


Token Ring uses a collision-free protocol (unlike to Ethernet - using CSMA/CD 
which has collisions). It usually runs on a shielded twisted pair cable 
(STP - IBM Type 1 or 3) or -on newer systems- on unshielded twisted pair (UTP - RJ45).
Usually the connector on the 'original' adapters is Sub-D 9 pin socket, compatibles and
modern IBM have often both: Sub-D and RJ45.

The 8228-MAU has IBM connectors .... these are hermaphrodites (no sex please) so they are plug and socket at once.
The IBM plugs are somewhat expensive. The cabling is simple and requires just a larger plier.
The Sub-D has to be soldered as usual ... one can build a TR-cable at home - I do this very often.
The cable might be a any good STP-cable ... or single-screened phone-cable for distances up to 30 feet.

The topology (physically) is a star - from the MAU to the stations with a single cable.
Logically it is a ring - 2 in one to be exact: one main-ring and one backbone. Therefore 4 wires.
A failure in one adapter or cable causes the MAU to drop only that connection but leave the rest active.
Unlike to Ethernet, where sometimes larger segments of the net are dead.

No need to have a dedicated server. Win95 or Windows for Workgroups runs fine on TR-Net.
16Mb/s cards can be configured to run at 4Mb/s ... 4Mb/s cards cannot run in a 16Mb/s net. You must decide.
4M-cards are cheap. The speed is reasonable anyway. Enough to copy data between machines or even
running entire programs from a machine acting as server at the moment. (some minor obstacles...).



Eeeech ... I didn't notice that your face turned green meanwhile ... is it so bad ?
You should have pressed CTRL-C sometime to stop me.
Your luck that my girl wants to go to bed ... and not without me. (Who else ?)


If there are more questions .... and I bet they are (now) ... leave me another note.


Very friendly greetings from chaotic Peter from Germany
"And you thought the people aren't taking acid anymore ..."