Archive Page 2

20
Mar
18

Trying the Campbell Cassette Interface

Some time ago I acquired an interesting bit of vintage tech, the Campbell Scientific C20 cassette interface. Since then it had been sitting on my bench looking lonely, I decided that I should at least try it out before I salvage any of the many useful chips it has inside. I have found a user manual for it along with information confirming that it is indeed what I thought it was, an interface for reading data encoded on audio cassettes by data loggers.

Not having any audio cassettes with appropriately encoded data however created a very simple issue. How exactly should I get it to do anything at all? It turns out whilst the C20 is primarily designed for reading from tape, it is possible to get it to write one as well, I thought we might as well look at the encoding on my oscilloscope and record a sample of the audio.

So I connected my oscilloscope to the output and a serial line to my old MS-DOS machine. After twiddling with the serial settings both on the machine and in Kermit I managed to get a welcome message and menu from the device which confirms that at least the CPU and serial lines are working. Unfortunately this is about as far as I have gotten.

The manual is exceptionally useful, providing not only information about basic use, but also more detailed technical information and example programs in basic for operating the device. I’ve translated one of these programs for writing data to tape, it seems the device is receiving the data I’m sending, but nothing appears on the output that I can see. I’ve not worked out if it’s something as simple as not connecting the scope correctly or if there is some hardware failure.

So unfortunately not as much to report as I’d like, but time has been quite limited and something is better than nothing. I’ll keep trying in the short term.

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21
Feb
18

MagiDuck for DOS

I was browsing the web recently when I stumbled across DOS Haven, A site devoted to home brew games made for MS-DOS machines. This is a welcome and quite unusual find as there isn’t much of a home brew scene for these machines as opposed to other platforms like the C64 or MSX which have a larger and thriving home brew community.

Though not featured on DOS Haven I found today’s game from a news item there. MagiDuck is an action platform game made for the IBM PC. It was made by Toni Svenstrîm with the latest beta release in 2016. It has especially low system requirements, only needing an 8088 @ 4.77 Mhz, CGA and 256K of RAM which covers pretty much almost any MS-DOS machine except those with MDA displays or small amounts of memory. The low system requirements come about partly because of the graphics mode used, which is a hacked text mode that allows for 80×50 with 16 colours similar but not the same as that used in Paku Paku.

Although the graphics are quite blocky due to the low resolution, the artwork is of quite high quality. Magiduck, the enemies and the levels are all colourful and cute. On the technical side the game animates quite smoothly on even minimal hardware and even manages vertical scrolling. Because early PCs didn’t have sound cards only PC speaker is supported, and the sound is fairly good for that device.

The game controls and responds quite well in a way that most PC platform games do. Although the key layout is a little different, z and x are used for jump and fire, it works just as well as the usual control and alt key layout. Magi jumps and moves as you’d expect, jumping around is fairly straight forward, which is good because the levels are quite vertical. Each level is basically a tower, you start at the bottom and work your way up to a star which represents the end.

I quite like the level design, like the sprites they are colourful and fun. There is some challenge, but not so hard as to be painfully difficult. Whilst they are quite narrow (a limitation of the engine is seems) there are a number of paths of varying difficulty through each level. You can spend time collecting treasure and keys from all the paths for extra points, or speed run the game for a time bonus.

Magiduck is technically very impressive and is very well designed and built. It does have some minor flaws, but generally they don’t impact getting enjoyment out of it. The hardware it can run on is very impressive, the original IBM PC was not considered capable of scrolling colourful graphics until later machines got much more powerful and the first EGA/VGA cards became common place. This game can do it on an original PC @ 4.77 Mhz and a CGA card. If you own an old machine this is certainly something you should give a try, you can find it on IndieDB here.

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22
Jan
18

Open Access for DOS

Open Access is an suite of office software made by a German company called Software Products International (SPI). We got this software with our first PC early 1990, but the software copyright is for 1986. Dad used the spreadsheet function to manage the farms finances until we upgraded to using Works a few years later, I used to experiment with the word processor and graphics (charting). I’ve been meaning to post about this program for a while, but I had difficulties getting it to install and work properly under dosbox. I eventually had to resort to a full machine emulator (pcEM), which would allow me to use all the components.

The word processor module is fairly simple, typing a document is fairly straight forward, but there are few features built in. Some notable omissions are a lack of spell checker and thesaurus. There are only a few formatting options, basically the usual bold underline and italics which are displayed as different colours. As a text editor it does serve it’s purpose reasonably well, but isn’t as easy to use as something like Works.

The spreadsheet module got the most use, mostly from my Dad. He said it was a big improvement over doing the books by hand, which was a tedious and time consuming job. This module is much more feature rich and would probably have been comparable with contemporary competitors. Something I did notice whilst playing around was that the formula system has a different syntax that I don’t remember. It’s possibly the same as Lotus 1-2-3 (as that was seen as a standard) but without the manual I can’t make full use of it. Something notable here is that values in formulae do not update automatically, you have to select the recalculate option to refresh those cells.

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The graphics module was for creating charts. It supported CGA and EGA graphics modes for creating the charts, although the emulation I have can only demonstrate the CGA mode. There isn’t any facility for entering data, instead you need to export a selection of data from either the spreadsheet or database module.

The info management (database) module was something we never used, and I wasn’t able to work out how to use it well enough to get a decent screen shot. Ironically it was one of the most popular features of the software that made it useful for many people. It supported a subset of the SQL language and was capable of storing what was an exceptional amount of data for the time. Later versions included a dialect of BASIC called PRO which made it a platform for developing database driven applications.

Using Open Access is not very intuitive for a user today as the interface is designed around using function keys on the keyboard. Unfortunately there isn’t really much documentation within the program itself, instead it comes with extensive printed documentation (which is presently at my parents place). At the time it was released this was completely normal, and if you used it often enough you’d soon remember all the function keys, so it wasn’t seen as a downside.

14
Dec
17

SS20 Desktop: Kernel Issues

Over the past few weeks I’ve been continuing my work trying to get the latest NetBSD working on my Sparcstation 20. The system has been hanging and I’d had trouble working out why, so I turned to reading as much as I could to see if I could find any clues. I found in the mailing list someone suggesting that not all SCSI drives are co-operative with the on board controller when running a MP (multi-processor) kernel on later versions, so I looked through my collection of SCA drives to see if I had a different model I could try. I found I had an IBM Ultrastar disk that is around 18G in size, so I swapped the Fujitsu drive (model MAJ3182MC) out for it. Surprisingly this made my system behave much better, it would install, and run on the uni-processor kernel with no issues at all where the fujitsu drives seemed to cause the system to hang frequently under disk access.

However booting with a MP kernel still would hang within about 20 minutes or during disk access, so it was at this point I joined the mailing list to ask others what I could do to resolve the issue. The people on the list are quite friendly and have been very helpful in trouble shooting. It seems that there are some kernel bugs related to MP that are present in 7.1 that are at least partially resolved in more recent versions of the kernel. Like most open source OS’s the current stable release is behind by a version or two from where the developers are currently working. It seems that there is some possibility of the fix being back-ported to 7.1, I tested out a patched MP kernel that was greatly improved in this respect. It still hung, but after a much longer period of time, and only when provoked by a specific program. Feedback from the mailing list also seems to indicate that choosing not to use the on board SCSI is another way that I could work around the problem.

So I now have multiple options for running my system. I could switch to using a single processor, I’d have the option of either a 60Mhz SuperSparc (currently installed with a dual 50Mhz module) or 75Mhz Ross HyperSparc, and everything should work well. Alternatively I could acquire an SBus SCSI card to connect my hard drives, or forgo a local disk entirely by using networking booting and a NFS share, both avoiding having to use the on board SCSI. Finally I could use the system as it is now with the patched 7.1 kernel, it worked well enough that this is quite feasible. I’m leaning towards booting the machine over the network at the moment.

In the short term with Christmas approaching, I’ll be putting the project aside until I have more time in the new year.

06
Dec
17

Loader Larry for DOS

Today’s game was made by Soleau Software, originally released back in 1993. The company was mostly one person, William Soleau, who was a prolific producer of shareware for MS-DOS machines during the early 1990’s, and is still developing new games today.

Loader Larry can be considered a more advanced version of Block man as it has more game mechanics, although the puzzles aren’t necessarily harder. Interestingly both games came out in the same year, I haven’t seen anything to confirm this, but I assume Block man came first as it is the simpler one. I also noted that Taking Care of Business is very similar as well, which makes me wonder if these games are a clone of something older that I can’t think of or find.

Graphically Larry uses pretty much the same technology that all MS-DOS Soleau Software games did, EGA graphics at 640×350 resolution. This has unfortunately squished my screen shots a bit vertically, so I’ve had to scale them to appear as they would on screen. Artistically it’s a little better than Block man with better detail in the tiles, but both are comparable given they use the same technology. PC speaker sound is present but fairly basic.

The controls are pretty much the same as those found in Block man, the movement however has been slightly improved. You can now turn around without moving a tile, and can pick up blocks that are under another. This makes it easier to move around in general, but care still needs to be taken so you don’t get trapped.

I found Loader Larry to be a challenging and charming despite its technical simplicity. It’s just the right amount of game to fill a gap where you need a bit of entertainment and challenge without being so big you have to invest loads of time. That being said you might not find it re-playable once you solve all the puzzles. Soleau Software is still around, so if you have nostalgia for these games you can still get them at their website, where they still offer registration for the MS-DOS games for $8 US.

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16
Nov
17

SS20 Desktop: Some minor progress

Whilst it has been some time since the original post, I have been a busy beaver trying to get the old Sparcstation 20 running. I’ve been making an effort to get the hardware working with some mixed success, and have made much better progress with the software.

The hardware is of course the much more pressing matter for obvious reasons. I had a recurrence of the problem I had with stack under run errors and just general problems booting in general. Of course this lead me to suspect the hardware, so this week I went about trying to work out what exactly was causing the issue. One way to help determine which part is at fault is by stripping the system back to the minimal and gradually add components while testing the system in between. Having removed most components the stack under run symptom didn’t disappear, trying each memory stick individually didn’t improve things, so I began to fear the worst as surely not all the RAM I have is faulty. It was at this point I decided to run the set-defaults command to reset the computers configuration despite not seeing anything there that should cause any issues, this funnily enough seemed to do the trick, as far as getting the machine to the open boot prompt without any errors and passing all the diagnostic tests with everything installed. I had to scale back to a 17G fujitsu HDD as the larger one didn’t cooperate with the system.

At this point I breathed a big sigh of relief as my hardware is probably in working condition. It’s booting the OS (NetBSD 7.1) and seems to run fine with one problem. Random system hangs. There doesn’t seem to be any pattern such as when the machine is loaded down or network access. I’m guessing that the kernel is having some issue and tries to hand control back to the system ROM, but this some how hangs/fails. I might try running the machine with out the X server in case it is stopping any errors from being displayed. I looked into the kernel messages and noted a few devices that may also be the culprit. The kernel is detecting the on board graphics (comes up as sx0 in the messages) even though I do not have a VSIMM installed, as I’m using a SBUS graphic board instead. The audio chip in my machine is listed as a DBRI, which is known to have issues with the current kernel driver. If you try to play audio in any manner the system hangs, it’s been a bug for a while, it kinda worked under NetBSD 4.0 when I last had that running. With this in mind I’m building my own kernel with the drivers for these two devices and other unnecessary devices removed.

I’ve had much more luck getting software to build in my emulated machine. I’ve got a fairly large collection of software to try out. Although I did have trouble much earlier on when either QEMU or the emulated machine would hang during a build. I can’t be sure if that’s down to the emulation or if it’s a genuine issue with the OS, and a possible cause of my problems on the real machine. Whilst I haven’t really changed anything in the emulation, it hasn’t hung for quite a while, so it’s any bodies guess as to the cause when it did happen.

Progress has been slow, but I’m gradually getting there! I’ve seen some cheap Ross Hypersparc 90Mhz modules that I’m considering buying as an upgrade.

26
Oct
17

6th Anniversary!

Wow time sure catches up on you fast, recently my blog had its 6 year anniversary. It feels like much less than a year, probably because of how busy I’ve been. This year I’ve obviously been doing less writing, mostly because of how busy family commitments are keeping me at the moment. It’s not all bad, as only posting once a month has allowed me to spend more time on each one, and I’ve made a few minor improvements to the layout and writing as a result.

I’ve only got one motherboard left for that series of posts and I’ve finished the graphic library bench marking, so I’m contemplating what new stuff I’ll make. I’ve been considering making a short series revisiting my old BASIC programs one at a time. Not sure how this will work out, or how interesting it would be to readers, but it’s some thing I’d be keen to do. A series for teaching programming to absolute beginners is another idea, which I’m considering producing in a video format on youtube. It would require a bigger time investment, but would probably work better than the written form.

I’ll continue writing about MS-DOS games, largely because there’s plenty of material left, and I quite like writing the posts. I’ve got some shorter term hardware posts in mind as well, such as a few system overviews and revisiting some of my neglected machines that haven’t had a run in a while or are in need of repair. The Sparcstation 20 is one such machine, I have already written the first post, but unfortunately I’ve had difficulty getting packages to build under system emulation with Qemu and NetBSD 7.1 as there are occasional unexplained freezes. I have the X11 server enabled which may contribute to that, so I might try disabling that, a different version of Qemu, or perhaps running the build on the actual hardware instead.

Before I wrap up, just a quick comment on something I’ve seen happening on Ebay. I sometimes peruse the vintage computing sections and couldn’t help but notice that some machines are being parted out (dis-assembled and parts sold individually) to the point where even screws are being sold individually. I’m in two minds on this, I can understand doing this for something that is broken, but still has some usable parts. On the other hand I would be really unimpressed if people did this to otherwise working hardware. It appears this is happening sometimes. Also unimpressive is when sellers label their common as mud machines such as the spectrum and C64 as rare even when they are anything but.

I’ll wrap up here before I launch into a rant about how hard it is to find retro hardware here. Big thanks to any regular readers and commenters.




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