Squirmer for DOS

I’ve started to recover from quite a nasty cold this week, so today we’re looking at another obscure MS-DOS game. It’s called Squirmer and was made by Stephen Lee Parker in 1990. It is an interesting take on the standard snake game that later became popular on feature phones.

Squirmer supports CGA, EGA and VGA as was common for many games of that time. The graphics aren’t spectacular, but are fine for what they are. The sprites are quite small, so there isn’t much room for detail, but this has the advantage of allowing larger levels on screen. PC speaker is the only sound hardware supported and is ok, but it can be switched off if you find it annoying.

The game-play is what makes Squirmer different. The main limiting factor in the game is the time limit rather than the length of your snake. There are the usual food pellets you can eat for points and increased length, but there are also bombs you can eat that will reduce your length. Care needs to be taken to not eat bombs when you’re not very long as that will kill your Squirmer.

You can move between the levels freely without restriction. All you have to do is go to the exit for the next or previous level. Your score increases more per pellet at the higher levels, so it can be worth skipping some of the lower ones, but it is worth collecting the extra time along the way as that is usually what runs out.

I found Squirmer to be a fun distraction, much like most other snake games, that can keep you occupied in a moment of boredom. However like other snake games you’re unlikely to play it for long bursts as the game-play is pretty much the same every time. It’s a little hard to find, but if you do happen to have it cross your path, it’s worth a quick play.

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Aldo’s Adventure for DOS

Aldo’s Adventure is a obscure little platform game released for MS-DOS back in 1987 by David and Ben Ibach. It is based upon a much earlier game called Ladder originally released for the Kaypro C/PM systems in the early 80’s. They have used the levels from Ladder with permission, so this is pretty much a port or graphical update for that game really. I found this game on a shareware collection disk that came with my copy of F19 Stealth fighter.

The graphics are EGA, and are reasonably well drawn, but what’s most impressive is the animation. The animation is smooth and flicker free, the player sprite has lots of frames of animation and appears to move quite well. However the barrel animation isn’t anywhere near as nice and there isn’t anything else animated in the game. Like many other small shareware developers, a high resolution mode (640×350) has been used, which means some EGA features couldn’t be used such as page flipping. This means all the screen updates would have to happen during the vertical retrace to avoid flicker, some slower machines wouldn’t cope very well. There is no sound at all.

Game-play wise it is pretty much a slowed-down version of ladder. The controls feel ok,but the pacing of the game feels a bit slow. With so few features, it sometimes feels like there isn’t that much to do, especially after the initial rush of barrels. To be honest because of the slowness the original on the Kaypro looks like more fun. You can find a little video of the Kaypro Ladder here on youtube, and a Java port here.

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Motherboard: ASUS SP97-V

Today we’re looking at another socket 7, the ASUS SP97-V. This particular model was made around mid to late 1997 judging by date codes, putting it fairly later in the life of the socket 7 standard. Some notable features include dual power input and optional on-board video.


Here is the board is all its glory, note how integrated this chipset is. There are far fewer chips on this board compared to the older Gigabyte board I photographed last time. This one has a SIS 5598 chipset, which whilst reasonably good hardware wise didn’t enjoy good software support under windows 9x.

PSU connectors

Like the Dataexpert board, this one comes from a transitional time for computer technology. However it isn’t the RAM in this case, the power supply connections reflect the change. Note it has both the old style AT connectors as well as the newer ATX one. The ATX standard is superior in terms of electrical safety, and cannot be connected incorrectly.

The board only supports 72 pin FPM or EDO RAM which was starting to be replaced by SDRAM at the time. I suspect the reason for omitting SDRAM sockets is to save money, as this would have been a budget board. The newer memory would have been more expensive per Megabyte, so excluding the sockets was probably not a big deal for cost minded consumers.

L2 Cache Like other boards this age it has L2 cache chips, in this case 512K pipeline burst cache. This is an important feature for faster processors that can consume data from the bus faster than memory of the time could deliver. For socket 7 boards in particular the bus speed would make a big difference to the maximum performance of the system as a whole. Later Super Socket 7 boards increased performance for pretty much any processor because of this.

From the perspective of a technician this board is pretty good. There are not too many jumpers to configure, and those that are present have a silkscreen label to aid setting them. The jumpers are mostly for setting parameters for the processor such as the multiplier, voltage, and bus speed. The manual wasn’t too hard to find on the web if you have any trouble, but you’re unlikely to really need it. I’ve not seen this board in service so I won’t comment on reliability. I’ve not tested this board recently but some of the VRM capacitors are bulging.

The fastest CPU it can support is the AMD K6-2 rated at 333Mhz equivalent. I doubt that part would achieve full performance on the particular board as the bus speed maximum is 75Mhz. I think a part of around 233Mhz would probably suite it better.

This particular offering from ASUS was obviously a commodity board with sockets for the older but cheaper main memory, the lower chip count and small form factor. The on-board video is a nice feature if you were trying to save cash, but would have been a problem for anyone looking for better performance. Although the RedHill guide says the graphic performance was reasonable compared to low-end cards. The other integrated features were pretty much standard for the time, but impressively are mostly integrated into the main chip. Only a few ports like serial and parallel have external chips driving them.


Hero’s Heart for DOS

Hero's HeartHero’s Heart is a puzzle game with elements similar to Boulder Dash and perhaps a little of Chips Challenge. It was made by Everett Kaser back in 1992, he is a one-man game company that made many DOS shareware games back in the day and is in fact still making new games. You can can check out his newer work on his website: http://www.kaser.com.

InstructionsLike most of his old games, Hero’s Heart uses EGA graphics in high resolution mode (640×350). This was common practise for one-man shareware developers even after most other game developers had moved onto using VGA. I suspect this is because old machines with EGA only cards were common and for puzzle games such as these the higher resolution afforded more game space without having to do the difficult coding for scrolling. Despite the limitations of only 16 colours in a EGA mode, the sprites and levels are quite pleasing to the eye. There is only a little animation, but what is there works quite well.

Come to think of it, this is something about most old DOS games that I do find rather nice. Looking over my collection of screen shots here in my media library I can’t help but note how colourful pretty much all old DOS games are. There are a few exceptions of course, but largely most are exceptionally colourful and nice to look at, even those with worse graphics. EGA graphics in particular, perhaps because of its limitations, seems to produce some of the more colourful scenes. Maybe it’s nostalgia in me talking.

All doneHero’s Heart features PC speaker sound, but it isn’t turned on by default. If you click the setup button there are options for turning the sound effects on and setting music for the theme and end of level. I’d suggest you should only turn on the basic sound effects as they are ok, but the musical options are fairly basic renditions of classical tunes that don’t translate well to PC speaker.

CreepersThe game-play is nice and relaxed as it is turn based. Every time you move, all other objects also get a chance to move. If you happen to trigger something like a falling boulder or arrow, quick reflexes won’t get you out of the way. The puzzle element is sort of like Boulder Dash and Chips Challenge, there are objects to collect (in this case hearts) and hazards to avoid. Boulders fall like those in Boulder Dash, but only when triggered by a nearby moving object. Balloons behave similarly only going up instead of down. Arrows point in any direction but otherwise behave the same.

Some parts of the puzzle are less hazardous, but still require thought. When moving onto or pushing something onto ice it can only move in a straight line until it hits something. Fire can’t be crossed without using an extinguisher to put it out first. Lumps of earth can also be pushed to put out fires, but are also useful to create land bridges over water, for longer stretches of water a raft is useful for crossing. Some of these are similar to elements found in Chips Challenge.

Ice islandWhilst the puzzles incorporate features similar to Boulder Dash and Chips Challenge, there are a few unique features such as bridges that roll out and hearts that require a specific enemy to walk into before you can pick them up. Also the construction of the puzzles is very different, the boulders aren’t the primary obstacle and most areas are open to movement for the player and hazards alike. The puzzles are all one screen in size, and so don’t feel like mazes which you could get lost in. So this really does feel different despite the similarities.

Water, bridges and rafts.So far the game has been challenging, but not frustrating, primarily because you can attempt any level as often as you like with no penalty. If you really get stuck you can always skip a level as you can select any puzzle in the set to solve. I’ve gotten about half way through the shareware levels and have frankly gotten stuck, but have at least enjoyed the journey to getting there. If you really enjoy puzzles you should give this one a go.

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Creating a Benchmark: part 5 – a road-block in testing

Some months ago I set about working on creating a bench mark program to compare the Borland Graphics Interface (BGI for short) with a hand coded in assembly VGA library. I had completed work on the library and even tested it on my Pentium 200Mhz MMX. So I decided to do the final tests to get the results when I ran into a road-block that still has me stumped.

I had three different setups to test the code on. Dosbox (at a fixed cycle count), my Pentium 200Mhz MMX machine running MS-DOS 6.22 and this machine (the last in the post), a 386sx running at 20Mhz. The BGI code runs fine on all three machines, but the hand coded library fails on the 386sx locking up during the first test – blitting sprites.

This was quite confusing as the test appears to at least partially work as a number of sprites are drawn to the screen quite quickly, but sometime during the test it always freezes. I thought about what could cause this and decided to try disabling interrupts during the drawing process. I did this as the main instruction used for copying bytes to video RAM does have an interrupt bug on older processors (286). This unfortunately had no effect. See this previous post to see code I used for copying memory.

Whilst disabling interrupts didn’t fix the problem, it did confirm which instruction was causing the problem. The rep movsw instruction was the only one I put between disabling and enabling interrupts (using cli and sti). When the machine froze with this change it no longer responded to keyboard interrupts that it did before. This indicates a crash during either an interrupt itself (unlikely) or this repeating instruction.

Given this strange problem I decided to test the machine by running memory tests and another graphical benchmark to see if there could be a hardware issue. It seems that the memory is ok, and it ran a 3d VGA benchmark with no trouble over night. I’ve also played some games such as Hocus Pocus that have parallax scrolling and would put a bit of load on the relevant parts with no problems.

So the question arises, am I putting too much data/strain into the Trident graphics chip for it to cope? I’m unsure if i can answer this. The process of copying the memory has several overheads. The processor has to read the word, write the word, increment the memory indexes and then decide whether to stop copying for each iteration of the instruction. This would at best be one word copied per 2 bus clock cycles, but is likely to be quite a bit slower, from memory I think like 6 clocks per memory copy for a 386.

I think it unlikely that I’m over taxing the graphic chip, but this problem does highlight one of the major problems people had when creating their own graphics libraries. Small shareware developers couldn’t have tested enough hardware to ensure that what they wrote would work on a large array of systems. The BGI however, having more resources behind it, has a quite good compatibility record.


Motherboard: GA-586ATE

Today we return to the series on motherboards with a Socket 7 Intel chipset board made by Gigabyte. The Socket 7 standard was popular in the mid to late 90’s, usually running Pentium and K5-K6 class chips. It would be considered unusual today as the standard supported CPUs from many different manufacturers, and was probably the last to really do so.


This board was donated to me quite some time ago, and luckily it works. Unfortunately the CMOS battery is dead and cannot be easily replaced on this particular board. At first glance this appears to be a high quality Intel chipset board with very few jumpers to configure.

GA-586ATE cache chipsThis board has some older style cache chips seen here, much like those found on old 486 boards. They are basic high speed static RAM chips, with the brains of the caching mechanism being embedded within the chipset. Being made in 1994 this would use the synchronous caching scheme as pipeline burst caching had not been released yet.

Unfortunately I couldn’t find any documentation at all so the detailed specs for this board are unknown. Although it is obvious that it only takes 72pin EDO or fast page RAM. CPU support seems to be up to 166Mhz from the jumper settings chart printed on the board.

CMOS and Clock chipHere is the annoying CMOS and real-time clock chip that has a built in battery along with the flash ROM chip. These chips are a pain in the butt because you can’t easily change the battery. I may be able to get a replacement, or I might have to hack this chip to disconnect the internal battery and attach my own external battery. Luckily this particular chip (and the ROM) are socketed so I shouldn’t have to do any soldering on the delicate main-board.

In service this probably would have been quite a good board and would have been capable of carrying some of the more cutting edge processors for the time. There are few jumpers required for set up, basically one set for the processor multiplier and another for the bus speed. The board silkscreen has enough details for setting the jumpers and the front panel, so the manual isn’t strictly necessary to getting this board up and running.

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These final two images are of the processor that is installed and the two main chips of the chipset. The processor is a pretty bog standard 100Mhz Pentium that performs surprisingly quite well. I had a quick look at benchmarks from the time and found it does nearly as well as some 120Mhz parts. This is likely due to limited memory bandwidth and perhaps the way the old cache on these boards worked. There is a socket near the main chipset that I haven’t seen before.

With no information available online there isn’t much more to be said about this particular board. It does still work, and if I can replace or hack that RTC chip it could be returned to service. The board feels and looks well made so I’d have to guess it was a higher end board, definitely capable of carrying a faster processor, and certainly quite reliable. It has managed to continue functioning even though it is a little over 20 years old. I guess technology of its era is more robust than much of what has come later.


Space Intruders for DOS

Today I played a clone of Space Invaders simply called Space Intruders. It was made by Softlair Computer F/X back in 1993. We got this particular game from a shareware magazine cover disc back in the day, it would have to be the only Space Invaders clone or otherwise that I really played at the time.

The game supports VGA graphics as you’d expect from a game of this vintage, and I think they are good, but not spectacular. The sprites are colourful and have some basic animation, but being a simple clone of space invaders there isn’t much more to be impressed by. Sound support comes in the form of PC speaker and Sound Blaster support, both of which sound quite good, albeit a bit loud. The PC speaker sound in particular is impressive as it sounds like it is producing digitised sound, but in higher quality than I’ve usually heard.

Game-play wise it’s pretty much just bog standard Space Invaders, although there is one minor change that makes a surprisingly large difference. With Intruder you can have quite a large number of shots in flight at a time, and the aliens also tend to drop many more bombs. This means you can put up almost a wall of fire and destroy almost an entire column of aliens at a time. Combined with a little dodging and you can quickly kill off an entire wave. This isn’t however the best strategy to use for getting a high score, for that you need to shoot the saucers that traverse the top of the screen for 1000-5000 points a hit.

As a clone of Space Invaders it’s not super faithful because of how much that one difference changes, but as a basic arcade shooter it’s pretty fun.

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