The RISC OS Time Machine
Lee Calcraft reviews the A440...
This review was originally published in the March 1988 edition of RISC User.
The entry price of the Archimedes 440 is around £2600. This is almost three times the cost of a 310, so what extra features do you get for your money? Externally the difference between the the 440 and the 300 series machines is minimal. All make use of identical system boxes, and the only difference in the keyboards is that the 440 has grey coloured function keys instead of the distinctive red colour used on the 300 series. At the rear of the machine there is again very little difference. All plugs, sockets and panels are identical except that the phono video socket on the 300 series has been replaced on the 440 by a pair of BNC sockets used for the attachment of a special high frequency mono monitor (video and sync).
Internally of course the machine looks quite different. It has a completely new PCB designed to accommodate 4 Mbytes of RAM. The strict upper limit for the 300 series is 1 Mbyte. There are three other obvious differences in the internal hardware. The machine houses a 20 Mbyte hard disc (of which more later), a small cooling fan, and a four-slot backplane, A backplane is essentially a board extension socket. The 300 series machines may be upgraded to take a two-slot backplane at a cost of around £40, but the 400 series machines provide four as standard. Of the four, slot number 2 may be used to hold a co- processor, and Acorn plan to have a floating- point co-processor board on the market by the last quarter of 1988. The 300 series machines by contrast, have no co-processor interface and may not be upgraded to take one.
The manuals and firmware of the 440 are again identical to those supplied with 300 series machines. The 440 is currently supplied with Arthur 1.2, and with Basic V version 1.02. Its processor runs at the same speed as that of the 300 series machines, and although the RAM chips in 400 series machines are somewhat faster, they are not clocked at a faster rate. The machines therefore perform identically, except where storage operations are involved.
The 440's internally mounted 20 Mbyte Tandon hard disc provides a welcome increase in both storage speed and capacity. It is a delight to use, and runs more quietly than many hard disc machines. The accompanying speed tests give some idea of its performance on 3 different types of test: saving and loading 80K screens using the *ScreenSave and *ScreenLoad commands, saving and loading an 80K block of RAM using *SAVE and *LOAD, and finally the PCW "Store" benchmark, which involves writing a 20 byte string to a file 1000 times in succession. I have given comparison timings for both 600K and 800K floppies. And you may well be more surprised by the relatively slow speeds attained with the 600K format ADFS floppy than with the high speed the Winchester. I should add that the 300 and 400 series machines give identical timings- all floppy disc tests.
New screen modes
Archimedes 300 series machines boast 21 screen modes, of which the top three (i.e. modes 18, 19 and 20) require a special multi- sync monitor. The 440 has two extra screen modes, labelled 22 and 23 (number 21 is "reserved for future expansion"). The two new modes are mono only, and require a further "special" monitor (in this case, one with a 96MHz line scan). Of the two, mode 23 is a text only mode, giving 144 characters on 54 lines (though you need a special 8x16 font for this). Mode 22 more usefully combines text (at 160 characters by 122 lines) with graphics, where it provides a resolution of 1280x976. This is very close to the 1280x1024 graphics units used on all versions of the BBC micro. The 48 missing vertical lines are taken equally from the top and bottom of the screen. As you will appreciate this is a very impressive resolution, and will be ideal for CAD and other graphics use, though lack of a special monitor prevented me from testing it out.
When you enter Basic on a default- configured 440 you are presented with the message:
Starting with 3698940 bytes free
There is obviously room here for some quite long programs! Exactly how much RAM is allocated depends, as it does with the 300 series, on the *CONFIGURE options. On the 300 series these allocations are all made in page units of 8K (except for FontSpace, which uses 4K pages). In 400 series machines, the size of page used for the *CONFIGURE command is four times as large (except for FontSpace which remains at 4K). Thus if you execute:
*CONFIGURE ScreenSize 10
you will allocate 320K of RAM to screen use on a 440.
The default *CONFIGURE options on the 440 are adjusted accordingly, and are given in the accompanying table. Software designed to run on the full range of Archimedes machines will need to take account of the new configured page sizes. Unfortunately there is no very easy way of distinguishing between the various members of the Archimedes range. The normally useful INKEY(-256) call gives the same result for all members, and is only useful for distinguishing between an Archimedes and earlier BBC micros. To use this test, type:
All Archimedes machines give the result 160. The test given in listing 1 will however distinguish between the two Archimedes machine series. It reads the MEMC status register, and prints out the machine series number by checking whether the memory page size is 8K (300 series) or 32K (400 series).
10 REM Tests 300 or 400 series 20 PRINT300-100*FNfour;" Series machine 30 END 40 : 50 DEFFNfour 60 SYS &1A ,0,0 TO reg 70 =(reg AND 8) =8
The added RAM, hard disc, ultra high resolution modes and the potential offered by the co-processor interface make the 440 a highly desirable piece of kit. Its high price will of course mean that only educational and business establishments will in general be able to justify its purchase. Home users who feel the need for the 4 Mbytes of RAM and high resolution offered by the 400 series machines will need to wait for the emergence of the 410 in the spring. This has no hard disc, and has 1 Mbyte of RAM upgradable to 4 Mbytes, but costs just £1608.85 for the entry level system.