DATAMATH CALCULATOR MUSEUM

TI-88 Versions

Collecting electronic calculators, you'll sooner or later understand the importance of the TI-88 - the holy grail for Texas Instruments aficionados. We learned with the Phoenix Project the Five Engineering Stages and applied them to the almost twenty different TI-88's we discovered so far. Digging deeper into the mechanical and electrical engineering of this fascinating calculator, we can define as of December 2020 a total of twelve different versions:

• TI-88 DVT 1 (Design Validation Test 1)
• TI-88 DVT 2 (Design Validation Test 2)
• TI-88 Clear-Case DVT 3 (Design Validation Test 3)
• TI-88 DVT 3 (Design Validation Test 3)
• TI-88 EVT 1 (Engineering Validation Test 1)
• TI-88 PVT 1 (Production Validation Test 1)
• TI-88 PVT 1.5 (Production Validation Test 1.5)
• TI-88 Firmware Engineering Device PVT 1 (Production Validation Test 1)
• TI-88 PVT 2 (Production Validation Test 2)
• TI-88 PVT 3 (Production Validation Test 2)
• TI-88 Clear-Case PVT 4 (Production Validation Test 4)
• TI-88 PVT 4 (Production Validation Test 4)

The differentiation between the three Engineering Stages DVT, EVT, and PVT is pretty straight forward with just glancing at the keyboard:

[ALPH] Key	[R/S] Key	Build:	Notes
		Design Validation Test	Grey [ALPH] key No dot next to [R/S] key
		Engineering Validation Test	Red [ALPH] key No dot next to [R/S] key
		Production Validation Test	Red [ALPH] key Red dot next to [R/S] key

We could analyze in the past years almost twenty TI-88 calculators and were looking into their Serial Numbers, Manufacturing Dates of the calculator, Markings on the Printed Circuit Boards (PCB) and more. Speculating about the reasons behind the cancelation of this outstanding calculator, we were looking closely into Markings of the Main Integrated Circuits (Part Designation, Revision, Manufacturing Code, Style of Marking). With some of the most complex Integrated Circuits (ICs) going through Revision "K" and sporting not even a Manufacturing Date Code while an earlier Revision "H" of the very same IC had final production status, we might have identified the reason for killing the TI-88...

Learn more about the Cancellation of the TI-88 on September 10, 1982 (long read).

TI Programmable 88 Versions

Serial Number	Build	Date of Manufacture	PCB	Main ICs	Timekeeping Controller	Master Controller	RAM #1	RAM #2	ROM	Diode-Mod
9-26-81-35	DVT 1	wk 39 year 1981	3500		2901 Revision - No Date Code Proto Package	2902 Revision - No Date Code Proto Package	TP0531NL P Revision - wk 35 year 1980 Series Package	TP0531NL P Revision - wk 34 year 1980 Series Package	Not visible Piggy pack	No
9-26-81-43	DVT 2	wk 39 year 1981	3500		2901 Revision - No Date Code Proto Package	2902 Revision - No Date Code Proto Package	531 Revision A No Date Code Proto Package	Not visible Piggy pack	5402 Revision B No Date Code Proto Package	No
---	DVT 3 Clear-Case	wk 51 year 1981	3500		01-186 Revision - No Date Code Proto Package	02-187 Revision - No Date Code Proto Package	TP0531 Revision B No Date Code Proto Package	Not visible Piggy pack	5402 Revision B No Date Code Proto Package	No
0000049	DVT 3	wk 51 year 1981	3500		01-186 Revision - No Date Code Proto Package	02-187 Revision - No Date Code Proto Package	TP0531 Revision B No Date Code Proto Package	Not visible Piggy pack	5402 Revision B No Date Code Proto Package	No
NTC-3-4-30-82	EVT 1	wk 17 year 1982	7999		01 PP Revision C No Date Code Proto Package	02 PP Revision C No Date Code Proto Package	0531 Revision BL No Date Code Proto Package	Not visible Piggy pack	CD5402 Revision C No Date Code Proto Package	No
0000337	PVT 1	wk 21 year 1982	8000		01 PP Revision C No Date Code Proto Package	02 PP Revision C No Date Code Proto Package	0531 Revision BL No Date Code Proto Package	Not visible Piggy pack	CD5402 Revision C No Date Code Proto Package	No
0000452	PVT 1	wk 21 year 1982	8000		01 PP Revision C No Date Code Proto Package	02 PP Revision C No Date Code Proto Package	0531 Revision BL No Date Code Proto Package	Not visible Piggy pack	CD5402 Revision C No Date Code Proto Package	No
0000341	PVT 1.5	wk 21 year 1982	8000		CD2901 Revision H P wk 27 year 1982 Series Package	CD2902 Revision H P wk 27 year 1982 Series Package	0531 Revision BL No Date Code Proto Package	Not visible Piggy pack	CD5402 Revision C No Date Code Proto Package	No
02 693	PVT 1 FED	wk 21 year 1982	8000		2901 Revision K No Date Code Proto Package	2902 Revision K No Date Code Proto Package	TP531 Revision C No Date Code Proto Package	TP531 Revision C No Date Code Proto Package	CD5402 Revision E wk 31 year 1982 Series Package	No
0001101	PVT 2	wk 32 year 1982	8449		CD2901 Revision H P wk 27 year 1982 Series Package	CD2902 Revision H P wk 27 year 1982 Series Package	TP531 Revision C No Date Code Proto Package	Not visible Piggy pack	CD5402 Revision C P wk 27 year 1982 Series Package	Yes
0001073	PVT 3	wk 32 year 1982	8449		CD2901 Revision H P wk 27 year 1982 Series Package	CD2902 Revision H P wk 27 year 1982 Series Package	TP531 Revision C No Date Code Proto Package	Not visible Piggy pack	CD5402 Revision E wk 31 year 1982 Series Package	Yes
0002023	PVT 4	wk 33 year 1982	8449		2901 Revision K No Date Code Proto Package	2902 Revision K No Date Code Proto Package	TP531 Revision C No Date Code Proto Package	Not visible Piggy pack	CD5402 Revision E wk 31 year 1982 Series Package	Yes

Diode-Modification

While analyzing the Printed Circuit Boards (PCB) of various TI-88 builds, we noticed with both the TI-88 PVT 2 (Serial Number 001101) and TI-88 PVT 3 (Serial Number 002023) a minor modification with two additional diodes near one of the battery contacts and the Peripheral I/O connector J2.

Reverse engineering the schematics of this modification we immediately understood:

Don't connect a CA-800 Cassette Interface or a PC-800 Printer to TI-88 calculators without the Diode-Modification!

The two additional diodes added to the Serial Input/Output (S I/O) pin at the Peripheral I/O Connector prevent the TP530 Integrated Circuits (ICs) inside the Plug-In CROM/CRAM Modules from a latch-up possible with the peripheral powered up and the TI-88 powered down.

If you have additions to the above article please email: joerg@datamath.org.