The Acorn Emulation Page - Growing Acorns

Growing Acorns

James Hope reckons the Arch doesn't get the recognition it deserves. All that could be about to change.

PC Emulator 1.6

Good news for those struggling to integrate the talents of the aRchimedes computer into an IBM environment. I've never thought that the original IBM emulator was much of a solution for those wanting to run some IBM software on an Archimedes, but the new version (1.6) makes me think again. The main and most substantial advantage is that the emulator runs properly under Riscos multitasking inside a window. Or at least it does if you are lucky enough to have at least 2Mb of memory and better still, an Arm3 processor.

Actually things aren't quite as bad as all that. What you get with the package are really two PC emulators. PCem is the impressive version which multitasks and needs the extra hardware, while a smaller and less demanding emulator, PCems, will run on a 1Mb computer. However, PCems can only run in full screen, and can only offer CGA-compatible graphics. But that's a neat compromise - necessary when you have a market of computers with such diverse talents.

For the non-Archimedes owners, here's a quick rundown of just how easily this sort of stuff works on the Arch. First off, the emulators are programs - they require no specialised hardware whatsoever. All of the chips which you find in an IBM-compatible - 8088, 8087 math coprocessor, 8259 interrupt control chip, 8253 timer chip and so on - are emulated in software. So to install either one of the emulators, all that is required is to run the program PCems or PCem. As soon as that is done, a window (in the case of the PCem program) appears onscreen and prompts for the insertion of an MSDos boot disk - just as an IBM computer would do. Thereafter, that's it - the Archimedes is now capable of running an IBM program alongside proper Archimedes software.

Good impression

So far we have an IBM running at about 4.7Mhz and with just the single floppy disk. I was hard pushed to find any reasonable software to try on the emulator that didn't need a hard disk, and that's the next step. When you first load the emulator, but befire you kick Dos into action, there's an option to configure the Dos environment. First you can set the amount of Arch Ram to allocate to the emulator. The default is 'all', which gives MSDos 640K. The next configurable option allows you to allocate up to four floppy drives to MSDos, which can appear on the icon bar alongside the Arch drives. The drives can be either 3.5" or 5.25", and can be shared by Riscos. The actual file handling between Riscos and MSDos-format drives is accomplished by the MultiFS program, which provides the same sort of facilities for Dos-format disks that you have for normal Archimedes disks. Files from Dos disks can be file-typed automatically, and this option is made flexible in that the user can edit the table which links Dos file extensions to Riscos file types.

The hard disk would have been a dream to set up if only I had got the space but, sadly, my hard disk is a rather humble, not to mention slow, 20Mb affair. Nevertheless, the emulator at least made accessing files very straight forward. Up to four hard disks can be created and all the user need do is to decide how big each is to be. One megabyte is the minimum and once you have settled on the size, you just tell the emulator to create it. What actually happens is that a Riscos file equal to the size of the hard disk is created on the hard disk and is placed properly inside the folder where you keep the PC emulator software. You will need to perform a number of esoteric MSDos functions to have the drive properly formatted. It must, for instance, be formatted and have the Dos system files transferred to it if you want to be able to bott the Dos emulator from the hard disk. This is preferable to booting from a floppy drive. But otherwise, that's all there is to it. The next time you load MultiFS, and extra icon will appear which represents the hard disk. MultiFS allows you to copy files from this disk in exactly the same wasy as if it were a floppy disk, except that - unless I have missed something - you cannot access the hard disk while the emulator is running. If you do, a message simply tells you that another application is using the resource. If you need to copy between Dos and Riscos from within Dos, then the utilities Getfile and Putfile are provided to achieve just that.

Another, and very significant, improvement is in the graphics capability of the new emulator. Those able to run the large emulator will be able to enjoy IBM software running in the widely-used VGA mode - mostly. And even the small version can offer CGA graphics, although I'm none too certain why anybody would actually want that. Another advantage of the big emulator is that it can dupe a PC to the extent of having two monitors attached. Programmers often like to have a colour VGA monitor and a mono display attached to the same computer, thus allowing two views of different activities. PCem can be set up to simulate that with two onscreen windows: one for the primary display, the other for the secondary mono display.

Which display standards you can use depends not least on your monitor. Those with medium resolution monitors will be confined to using the EGA option in CD (colour display) mode. If you have a Multisync or VGA monitor, you can pcik EGA+ and ECD (enhanced colour display) and run most VGA software. I say most because Acorn admits that the VGA implementation is not complete, hence the EGA+ tag. EGA+ is a partial implementation of VGA, and running it will require more that 2Mb of Ram. But it is useful if you want to run Windows or a flight simulator, which should both be installed as if running on a VGA computer. There are going to be problems with software that thinks it is writing directly to a VGA screen, so don't be surprised if some software crashes out of sight. Even the EGA mode, which has a couple of facilities missing which aren't in themselves very important, might prevent some games from working if they insist on using some special EGA modes. When using the higher modes for graphics, screens can be captured from IBM software as sprites. On the mono system, the screen is written out as text when captured.

Mice and easy

A mouse comes with the graphics software. Acorn has solved the problem for those who want to use a mouse by offering a special mouse driver which is loaded with MSdos and which allows you to usethe Arch mouse as if it were a Microsoft serial or bus mouse. Should you be desperate enough, here is all you need to run Microsoft's inferior GUI on an Archimedes. I say mad enough because if the emulation is impressively correct in all important respects, it is certainly correct as far as speed is concerned. This is, after all, an emulated 8088 computer. And I don't know about you, but I have read in Shopper more than enough literature about how such a computer is simply not qualified to run Windows. It is too slow. This is not an alternative to a fast 80286 computer, not by a long stretch. But if you simply desire access to a PC-based machine for the odd job, PCem is wonderful. I can now use it without ever leaving Riscos, to compress and decompress files which don't fit onto a standard Dos disk. I can also take files for particular word processors, and edit them in their native program, while at the same time laying the text out in Impression.

PCem is a commendable improvement over previous versions and still, I believe, unique for being the cheapest IBMemulator for any computer and one of the very few that does the job without compromising the native operating system. And it does this entirely by using software. A remarkable piece of code. One of my favourite features is the way you can set the configuration line to be passed onto Dos, to automatically set up and run particular applications. By saving the different commands files with appropriate names, and by executing them rather than the PCem icon, you can effectively run any IBM program as if it were a Riscos program; directly from desktop.

Emulator-compatible
dBASE IV
Retrieve
Neris
Excel
Lotus 1-2-3 v2.1
SuperCalc 4
Symphony
Harvard Graphics
Windows 3
MS flight simulator
Turbo Pascal 5
LocoScript with Bios Scroll
Microsoft Works
Timeworks
Ventura
DESKpress 1.01
WordStar Prof 6
WordPerfect
PC Planner
BYL
Corsstalk
Procomm
MASM C V5
Quick C
GWBasic
Smalltalk V
ProFortran77

Incompatible
DRDos Filelink
Desklink
Zortech C+++
Any software which is copy protected using a dongle on the parallel port

Under Scrutiny
PC Emulator V1.6 £99 plus Vat
£29 upgrade from previous versions
Excellent software IBM emulator
Acorn Computer Dealers
(0223) 245200

The Acorn Emulation Page - David Sharp