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Saturday, 3 November 2018

Toshiba T1000 Part Three: Technical Overdose

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Intro


Welcome to part three of an epic feature on the Toshiba T1000.

Part one details the history of this computer more extensively.
Part two (written first, oddly) shows in-depth the steps required to restore a non-working machine to full health.
Part three is an attempt at a definitive technical run-down.

Datasheet


Toshiba published a datasheet on the T1000. I'm replicating some of it here to make it more searchable, but it does include quite a bit of info I deliberately left out. Please refer to the datasheet if you do want to know about shortcut keys, environmental specifications, options and accessories, and technical info like memory map, interrupts and port assignments.

Model number: PA7027U (FCC ID# CJ69XAE250) Dimensions: 12.2"W x 2.05"H x 11.0"D
Weight: 6.4 lbs.
Voltage: Computer DC input - 9VDC 1.1A (+ = core; - = shell)
AC adapter - 120VAC (108 - 132V), 60Hz, 15W
Battery: Rechargeable internal NiCD battery pack (1300 mAh)
CPU: 80C88, 4.77 MHz
RAM: 512KB standard (conventional)
(Memory expandable to 1.2MB when optional 768KB LIM-EMS 3.2 / HardRAM card added)
Video RAM: 16KB
Number of keys: 82
Keyboard type: Selectable between PC or 101-key keyboard compatible
Drives: One 720KB 3.5" floppy disk drive
Operating system included: Toshiba MS-DOS 2.11 in 256K ROM

Motherboard


A complete XT clone on one board. Pretty impressive, huh?

T1000 Motherboard. Source: Author.

Display Controller  Subsystem





HM6264LFP-15T (IC36, IC37) are 8-bit high speed CMOS static RAM manufactured by Hitachi. Each chip is 8K for a total video RAM of 16K with 150ns response time. This equates to an operating frequency of 6.66MHz.

DC2054P138A (IC31) is Toshiba's gate array for controlling the dot matrix display and external CRT. There is no published datasheet, but technical details for all the proprietary ICs may be found in the T1000 maintenance manual.

TC53257F (IC32) is the character generator ROM.

Chipset



You can see from the main photo that the large chip T7885 (IC15) is the super integration (SI) gate array, based on its size and position. It's the key to the T1000's compact form and integrates the functionality of the following discrete ICs:

- 82C84 clock generator
- 82C88 bus controller
- 82C53 programmable interval timer
- 82C59 programmable interrupt controller
- memory and I/O address control
- system bus control
- 82C37 DMA control unit
- 8565 real time clock

It also interfaces with the speaker, keyboard (80C50), floppy drive and external bus.



DC2130P174A (IC21) is the I/O controller gate array and includes the following functions:

- printer interface
- I/O address decoder
- system RAM controller
- DOS ROM controller
- system support port

IC35 is a microcontroller based on the 80C50 and is utilised as the keyboard controller.

TC8570F (IC11) is the UART chip.


Finally, TC8521P (IC3) is the RTC & CMOS RAM. Although it isn't Y2K compliant, Toshiba have implemented it in a clever way as to make the actual computer compliant. The RAM holds the system configuration

CPU and RAM




OKI's version of Intel's 8088 was originally designed by Harris Semiconductor and is basically an Intel 8088 but fabricated using CMOS manufacturing process. This reduces power consumption compared with the original part while maintaining full software compatibility. It is 16-bit internally, with an 8-bit data bus and can address 1MB of memory. The RAM chips are Toshiba model TC514256PL-12 (IC17-IC20), also CMOS parts. With a 12ns access time, they can operate up to 8MHz. Each chip obviously provides 128KB of memory

Display



The dot matrix panel has a resolution of 640 x 200. The driver board holds eight T7778A (labelled XD1-XD8) column drivers, each driving 80 columns, and four T6961B row drivers (YD1-YD4). There are no datasheets available online. Interestingly the T7778A is the same one as found in the Texas Instruments TI-81 programmable calculator from 1990.

At one point, Axonix provided a service to retrofit a backlight to the T1000. This was not a trivial upgrade as it took 5 days, added weight, increased power consumption and worsened the readability of the display without the backlight. It's possible there's a way to do it using more modern technology but I think too much could go wrong for it to be worthwhile. Get yourself a T1000SE if you want a backlit screen.

Floppy Drive

The T1000 comes equipped with a 3.5" floppy drive. This is a double-density, double-sided, double-track drive supporting 720KB disks. These are the specs according to the maintenance manual.
Storage Capacity (kilobytes): 1000 (unformatted), 720 (formatted)
Number of Heads: 2
Number of Tracks per Side: 80
Track to Track Access (ms): 6
Head Setting Time (ms): 15
Track Density (tracks/s): 135
Motor Start-up Time (ms): 500
Data Transfer Rate (kilobits/s): 250
Rotational Speed (rpm): 300
Recording Method: MFM

Software


TC532000P is a 2Mbit mask ROM and holds the operating system. TC57256AD-20 is the BIOS ROM.

There are two known versions of the BIOS (I'll dump mine at some point in the future for reference):

026C: v1.10, 29 June 1987
026F: v4.10, 2 May 1988

As mentioned, the T1000 avoided inclusion of an additional floppy drive with Toshiba DOS 2.11 / R2A on mask ROM (If a mask ROM is like a CD-ROM, an EPROM is like a CD-RW). The ROM in my T1000 was created on March 17, 1987 according to the readout from CHKDSK.EXE. It has the volume label IC-DISK ROM and includes the following DOS-related files with the same date stamp as the ROM:

ANSI.SYS
ASSIGN.COM
AUTOEXEC.BAT
CHAD.COM
CHKDSK.COM
COMP.EXE
CONFIG.SYS
DEBUG.COM
DISKCOMP.COM
DISKCOPY.COM
EDLIN.COM
FIND.EXE
FORMAT.COM
GFTABLE.COM
1902
904
106
6353
6468
8318
160
12146
10011
10329
4389
6331
6240
3243
GRAPHICS.COM
KBOARD.SYS
LABEL.COM
MODE.COM
MORE.COM
NOW.EXE
PRINT.COM
RECOVER.COM
SELECT.EXE
SORT.EXE
SYS.COM
TREE.COM
VDISK.SYS

973
4431
1280
2377
4364
5410
4515
2295
11022
1632
1920
1988
1286


The following Toshiba programs are also included, with date stamp June 11, 1987. Based on this, it can be assumed that a T1000 with either BIOS listed above has the same DOS ROM:

EMM.SYS
COMMAND.COM
SETUP10.EXE
TEST10.EXE
8691
16598
10224
17648
Driver for RAM expansion card
Toshiba DOS command interpreter
T1000 setup program
T1000 diagnostics program

There is also a folder called KB1000, which has keyboard drivers for Spanish, German, French, UK English, Italian, Danish, Swedish, Netherlands (Dutch) and Slovakian.

Here is a printout of AUTOEXEC.BAT:

echo off
echo
path c:\
NOW
echo
if not exist D:autoexec.bat goto No-IC
D:
autoexec
:No-IC

Config.sys has one line:

Country=001

The ROM effectively simulates a floppy disk in the way that it is organised. John Elliott's T1000 page goes into all the detail you could possibly need to know about the ROM itself so there's no point me replicating it here.

I've seen it alleged that Toshiba offered ROM upgrades for sale to provide a more recent version of DOS than 2.11 for the T1000 but it seems these were never available.  Given that DOS 2.x was released for the IBM PC XT originally, it's pretty much the appropriate version for this computer and there would be limited practical advantages to upgrading it if you're using period-correct software. DOS 3.x mainly brought with it enhancements to hard disk partitioning and high density floppy disk support anyway, and these are redundant with the way the T1000 is configured.

You can boot DOS 5.0 via floppy disk, but the ROM will not be recognised. It is also possible to burn yourself a ROM with a different operating system and / or additional software.

Method 1: DISK2ROM


John Elliott actually went to the trouble of writing a program that converts a floppy disk image into a format that can be either burned onto an EPROM or run in an emulator. One issue with this method is that you have to use the version of DOS that came with the T1000. This is because the ROM image has no partition table and versions of DOS after 2.x don't recognise this configuration. It's certainly the simplest way though, and the files can be downloaded using the link above.

Method 2: Manually


A dude called Kent Nickerson provided a guide on comp.sys.laptops (a newsgroup, now archived on Google) having successfully upgraded the stock 256KB EPROM with a 512KB part. This allows the user to include an updated operating system and additional software and he even provided a service for people who wanted an upgrade but didn't want to do it themselves (it's... complicated). Apparently some people reported problems with their replacement ROMs so he gave up, but it worked at least once for him. In case the guide becomes unavailable, I have created a PDF version that can be downloaded.

Method 3: Use the Hard RAM


If you have the RAM card installed, there are two ways DOS 5.0 or later can be used. The original guide is archived here:

KnowledgeBase Archive
minuszerodegrees.net (PDF)

Essentially you can either reconfigure the RAM card as drive C, or boot from floppy and use the RAM as static storage.

That's all I can be bothered to write at the moment. As and when I decide to add more, I will.

Revisions

18th Nov: added information on floppy drive.
12th Feb 2020: formatting changes so it's less broken. PSU info. Replicated some info from the Toshiba's 'datasheet' of the T1000.

1 comment:

  1. Have you by chance dumped the image of the rom dos? I have a T1000 with a faulty rom.

    ReplyDelete