|18 : Expansion|
Acorn have released (Summer 1988) a version of DOS Plus modified to allow the 512 to be used on an Econet local area network. The software is based on Digital Research's DR-NET, suitably adapted to take account of the 512 hardware and the Econet fileserver requirements. When used, this software permits a BBC or Master fitted with a 512, to run DOS Plus in the normal way, but at the same time provides shared access to the fileservers' disc drives and printers. Connection is via the standard Econet port in the I/O processor.
The package consists of the adapted software and a site licence for its use. The software comprises a new version of DOS Plus, together with the additional transient commands to take advantage of the network's facilities. The use of DOS Plus with Econet has no effect on any other machine in the network, any or all of which may be run in native mode, or if fitted with a 512, as a DOS Plus system, at the same time. The package's title is DOS Plus with Econet Software, and it can be ordered under code AES39 from Dabhand Computing on 061-766-8423.
At various points through this guide consideration has been given to the memory constraints of the 512 running under DOS Plus. This limit on the memory available applies to all transient programs (ie software loaded from disc) and is, in part, due to the memory requirements of DOS Plus – 90k larger than, for example, MS-DOS. Some applications need 512k or even 640k when running under MS-DOS – so these clearly will not run on the 512.
Solidisk has produced an upgrade for the 512 which overcomes these problems, the PC Plus, by adding an extra memory board to the 512. In order to have this upgrade fitted, you must send your 512 board to Solidisk, who will fit the PC Plus to the existing 512 board, as it requires a number of soldered connections. The following points are made for information only, and no criticism of the PC Plus is implied or should be inferred. In fact, reports on the issue two board by Acorn staff, who have examined the product with regard to power consumption, build quality and operation, are very favourable.
You should be aware that, altering the hardware in any way necessarily invalidates any Acorn warranty applying to the original board, and you must sign a disclaimer acknowledging this. This does not absolve Solidisk of the consumer's rights in terms of the supply of goods, standard of workmanship and fitness for purpose, but neither does it transfer responsibility for the original board to Solidisk. You may wish to seek clarification from Solidisk and, if appropriate, take further advice before signing the disclaimer. The PC Plus requires no additional documentation and is attached in exactly the same way as the original 512 board, as shown in the Acorn documentation.
Should you be running a version of DOS Plus earlier than 2.1, you will also need to return the DOS Plus disc (Issue DISC 1) so that the software may be altered to allow the extra memory of the PC Plus to be used.
In use, the PC Plus behaves just like the original 512 upgrade, but with the benefit of the extra memory, which will be used automatically by most software. The only real change concerns the memory map, if you are using version 1.2. It is identical to DOS Plus version 2.1 which is already amended to allow for this upgrade.
The additional memory provided by PC Plus may be used by any program running under DOS Plus, so long as that program does not itself impose a limit. For example, Lotus 123 will happily use the full 700k left after loading DOS Plus. This means that PC Plus actually provides more memory than the 640k available under normal operating conditions with MS-DOS. However, this is an exception, and most software will not use in excess of 640k, even if it is available.
All the applications tested which need more memory than that provided by the standard 512 upgrade (and which are not prevented from running by other problems, such as hardware addressing) run on the PC Plus. As with any product, if the information is not available for a specific package that you wish to acquire, ensure that you can test it before purchase, or better still, obtain from the retailer a guarantee of a refund if the package proves unsuitable.