The Sinclair family of computers were conceived and developed by Clive Sinclair who was well known in Great Britain as a very innovative electronics kit designer. His trade mark was advanced capabilities with a reasonable price (and, unfortunately, with some. design problem which limited the utility). But his ZX80 and ZX81 kits were wildly successful and introduced a very large number of people in the United States and the rest of the world to personal computing at a reasonable price.
There are in the United States seven models of computers in the Sinclair family, some of which have several variations. The following table summarizes some of the more important features of the various models.
| Name | ROM | RAM | Speed+Monitor | Keyboard | Language |
|---|---|---|---|---|---|
| ZX80 | 4K | 1K | fast | membrane | integer BASIC |
| ZX81 | 8K | 1K | fast and slow | membrane | Sinclair BASIC |
| TS 1000 | 8K | 2K | fast and slow | membrane | Sinclair BASIC |
| TS 1500 | 8K | 16L | fast and slow | chiclet | Sinclair BASIC |
| TS 2068 | 24K | 48K | color | chiclet | Sinclair BASIC |
| QL | 48K | 96K | color | key | SuperBASIC |
| Z88 | 32K | LCD | key | BBC BASIC |
There are a number of comments which can be based on this table. Many of the ZX80 and ZX81 computers were built from kits. Only a modest amount of kit building experience was needed to do a good job with these well-explained kits. A series of computers called the MicroAce were sold for a which in the US. These computers were basically the same as the ZX80 and were sold under a license from Sinclair. The two companies had some disagreements and the Micro Ace people were active for only a short time.
The major difference between the 4K and 8K ROM’s lie in the way numbers and strings are handled. To save space, the 4K ROM contained a version of BASIC that handled integers only. Programs written for one of these ROM’s must be translated before they will work with the other ROM. When the ZX81 was introduced, the 8K ROM’s were available to partially update the ZX80’s. However, another modification had to be made to the ZX80 in order for it to do action graphics. Action graphics are possible because of the “slow” mode of operation where the computer displays something on the TV screen continually and does the computing only between pictures. This mode can be simulated on an ZX80 with the 8K ROM by imaginative use of the PAUSE control.
The TS1000 is basically the ZX81 with a few minor changes. The first is the inclusion of a 2K RAM. Because much of the 1K RAM in the ZX81 is used to hold information for the TV screen, the addition of 1K more RAM more than doubled the memory available for programing. (it is relatively easy to convert the ZX81 to 2K RAM, by the way.) The TS1000 also had a new instruction book that tries to be a bit easier to read but does not give any more information. The main circuit board has a slightly different layout so if modifications are made, by sure you know for which board the modifications were designed.
The models with the TS prefix were sold in the US by the Timex Corporation. Unfortunately that company pulled out of the computer business after putting a lot of effort into the development of the TS2068.
Computers similar to the TS2068 were very popular in Europe, particularly as game machines under the name of Spectrum. There were a number of Spectrum models developed, some quite sophisticated and all quite cost effective. There are a few differences between the ROM for the TS2068 and the Spectrum models so the programs are not interchangeable. Few Spectrum models were sold in the US, so QZX does not run any Spectrum specific articles. Many US users have modified their TS2068 computers so that a Spectrum ROM can be switched in and Spectrum programs run.
The Sinclair BASIC for the TS2068 is similar to the BASIC for the ZX81 with the addition of quite a few commands. The character set is quite different however. The most notable difference is the addition of lower case letters.
All the computers can support additional RAM with ease. There are many 16K RAM add-ons which plug into the ZX81, TS1000, and TS1500. These are now very inexpensive and almost everyone has one. Additional memory for the QL and the Z88 is more expensive.
Other than running small programs, the most intensive amateur use of these computers is for CW, RTTY, and Packet. For these modes one must consider the keyboards. It is hard to touch type on the first four computers listed in the table. Another difficulty is the character set. It is not directly compatible with the ASCII character set assumed by most communications programs. Refer to back issues of QZX for articles on converters and other means to circumvent this problem.