This 8-Bit Computer Has Two CPUs (And One Acts As A GPU!)

this rare Japanese Spanish computer not only has two CPUs but one of them is acting as a full Graphics co-processor this is honestly one of the coolest architectures I have seen in quite a while a few years ago a friend of mine in Spain gave me this computer it's called a seikoinsa fm7 and a new absolutely nothing about it but I love learning about and tinkering with computers of this time period so I was instantly attracted to it what is it what's under the hood what can I do what kind of software is there for it and how come I had never heard of this computer in my life we'll answer all those questions today but let's start by having a look at the outside of the computer it's actually really heavy and Hefty it weighs 4.5 kilos which is a lot more than most similar computers the bag has a lot of different ports the power connector is just for standard computer cable so that means the power supply is internal which partly explains why it weighs so much apart from that it has a reset button an audio cassette board a color CRT and a monochrome CRT connectors a speaker connector to volume control knobs then it has an expansion port a printer port and a block of dip switches it certainly seems to have a lot of options for expansion but wait we're not done yet you can lift the cover over the keyboard and you reveal three more expansion slots they were serious about expendability here it has a very nice full-size keyboard I don't think they're mechanical switches or anything like that but still it has a pretty good feel to it the keyboard layout is relatively modern except for a few details like the double row of function keys I find it quite interesting that the keyboard is somewhat localized for the Spanish Market it has the Enya key and question marks but they didn't bother translating shift keys or anything else for that matter the name fm7 gives us a really good hint about the origin of this computer and there's even a Fujitsu logo next to the keyboard flipping it the full secret is revealed this seems to be a Fujitsu fm7 microcomputer and it appears to have been localized for the Spanish Market by the company Seiko insa so let's open it up and see what we find inside thank you [Music] wow this is impressive there's a lot of integrated circuits and is very well laid out this uses the space very well lots of things are socketed I mean the whole thing just oozes quality [Music] the first surprising thing about this board is the amount of ICS most of them are manufactured by Fujitsu by the way it's packed full of discrete logic chips all over the place some people might be put off by that but I actually really like it it makes it much easier to repair than having the logic all concentrated in a single custom chip like some lighter computers on the other hand this is already a redesigned version of the fm7 board with some of the logic already combined in a few chips the original fm7 board really was packed with chips it's a bit hard to make out the structure of this board and I couldn't find any schematics for this particular version so I'm just going to have to do my best and make educated guesses about what's going on let's start with the CPU a 6809 running at 2 megahertz like the CPU found on the dragon or the TRS color computer that's probably why sometimes you'll hear somebody refer to the fm7 as a Japanese cocoa but I don't agree with that at all and we're gonna see in a second why that is and over here we have another 6809 what's going on the fm7 used a second 6809 CPU as a graphics co-processor that is something pretty unusual for computers at the time at least the ones I'm most familiar with it goes to show that Fujitsu really wanted to push the power of this computer instead of just focusing on making the cheapest architecture possible like instead of spectrum having a second CPU opens up all sorts of possibilities the main CPU can just tell the second CPU to draw a line and then move on to do other things while the second one goes through and all the calculations to draw that line in a way it's a parallel architecture somewhat similar to the modern CPU GPU split I don't think it's possible but it would have been really cool if you could upload small programs to the second CPU and in a way create custom shaders in addition to the graphics GPU we still have what seems to be a CRT controller I'm guessing that's in charge of generating the addresses for the image that needs to be generated at each point time and near there we have another chip in charge of generating the right RGB signals from the pixel values we have a couple of ROMs on the board they each seem to be 32 kilobytes although the fm7 is listed as only having 48 kilobytes of ram I wonder if it was just easier to round one of them to 32k or if there's really something extra in the 16 kilobytes I was asked to do a dump of these ROMs for preservation since this machine isn't very common so let's do that right now and we can see if there's really any extra data on the 64 kilobytes I'll pull the chips out and I'm going to use my usual eprom programmer to read them back these are custom flash ROMs but they're pin compatible with the 27c 256 so I'll just choose that from the menu and read all the data and then same thing with the other one I'll put a link in the description to where you can download these ROMs if you want to now I can look at the dump with a Binary Editor and the first ROM has data in the full 32 kilobytes and it seems to be totally unique the second one seems to also have 32 kilobytes but if we look carefully at the halfway point at 4000 which I see that it's repeating the first 16 kilobytes which makes sense it matches what we're expecting from the fm7 okay back to the board and over to the left under the built-in speaker we have a very standard 64 kilobytes of dram split into eight ICS of 64 kilobits each importantly only the main CPU has access to those things get much weirder with the video RAM though over there on the right we have six ICS of 64 kilobits each that makes a total of 48 kilobytes which is the amount of vram we expect but it's in a very odd configuration we only have six ICS but normally you'd expect to see eight to be able to read a byte at the same time I try to make sense out of this by looking at the schematics for the fm7 but unfortunately I was only able to find the ones for the original fm7 board not the revised one there they show three Banks of eight ICS each and each IC holding 16kw bits that actually makes a lot of sense each pixel can be eight different colors so each Bank holds one bit for each pixel so to generate the color of a pixel they need to read the same address from all the banks and then shift the resulting three bytes until they get the right three bits to determine that color so how does that translate into six ICS of 64 kilobits each well it turns out that these RAM chips are four bits wide which I didn't notice at first so they're clearly doing some kind of mapping from Pixel addresses to a combination of bits at first I thought that maybe they were only using three bits in HIC one for each color Channel like in the previous board version and maybe they were just ignoring the fourth bit which would be wasteful sure but sometimes you need to do that to keep things simple but let's do a quick check and see if that's possible since we know that the fm7 has a fixed resolution of 640x200 and no pallets or any other data that needs to be stored in vram we can quickly calculate the amount of memory required for the screen so 640 times 200 that 128 000 pixels and since each pixel takes three bits that comes up to be 48 000 which is very slightly less than the 48 kilobytes available but not enough to avoid using a bit in each IC this actually makes me wonder if the system uses that extra 1152 bytes for anything so knowing that here's my best guess of how the system can map 48k of screen memory into those ICS the six ICS can be separated into two groups of three ACS each one group contains all the data from half of the screen and the other group the other half HIC in a group contains a bit towards the color value of a pixel so one I see will have all the red bits one all the green bits and the third one all the blue bits since reading from a single address of those ICS will generate 4 bits in each IC the result will have to be passed through a multiplexer to select the right bit and come up with the three bits for the color of that given pixel so in the end that's actually pretty close to the original fm1 board design but but just with many many fewer ICS anyway the weirdness isn't over yet because I noticed that there's still more RAM on this board there are three ICS with two kilobytes of static Ram each there's no mention of that extra Ram anywhere on the fm7 spec but looking at the block diagram for the computer gave me the hint to realize what that was the top half is related to the main CPU and the bottom half is related to the sub CPU in charge of Graphics the SRAM is that block in the middle and if you look at it it seems to be the main way that CPUs can communicate with each other it turns out is very similar to the way a CPU and a GPU would communicate through a command buffer there the CPU can put commands for the graphic CPU to read them back and execute them so it's very very interesting architecture well some engineer over at Fujitsu was really like in this parallel decoupled architecture because they decided to use it one more time in the same computer down here we have a 4-bit microcontroller so it has its own tiny CPU small amount of ROM and RAM all built into the same IC it takes care of the keyboard not surprisingly since the keyboard connector is right next to it and it turns out one of the other two kilobytes of static RAM chips is located right next to it so I'm going to guess that it also communicates with the CPU via that shared Ram apart from that we have an AI sound chip very similar to the one found in many other computers like the amstrad CPC or MSX computers for a change this one is just hooked up directly to the CPU without any strange architecture I actually just noticed this chip over here with a label and it also looks like it's a ROM I'm surprised because we already found the 48 kilobytes of ram but again reaching for the block diagram I'm going to guess that this ROM is for the graphic CPU so I suppose it's possible that they didn't count it for marketing purposes in any case I suspect it may contain instructions for the 6809 CPU to execute the graphics commands so when the main CPU tells it to draw a line from X to Y it calls a function on that ROM and executes that it looks like is just two kilobytes though which seems awfully small for any kind of graphic command I wonder why they didn't use something larger since the ROM seems to be pin compatible with an m2716 I read it back with the eprom programmer again and this is even more surprising about a quarter of the ROM is empty I wasn't expecting that I wonder if this is just some kind of jump table instead of all the instructions for the graphics commands and finally apart from the huge amount of glue logic all over the board we have several pretty hefty ICS around here searching for those numbers doesn't bring up anything specific so I'm going to guess those are all custom Fujitsu getaways combining a lot of the logic in the original fm7 board and that is one of the downsides of having so many different Rams and ways to get data to and from them you end up needing a lot of logic to select one set of signals or another and that increases the cost of the computer but they sure created an interesting architecture I'm curious about this power supply because I was hoping to take this computer to the US with me this power supply requires 220 volts but since in Japan they use 110 volts I was hoping it would have some way of toggling it to use 110. a bit like the BBC power supply but I'm not seeing anything of the swords so I'm afraid they might have made a custom power supply for the Spanish Market in that case I'll either have to hook it up to my 220 volt transformer or maybe I'll have to adapt it with a custom power supply in the future we'll see so yeah it seems that this computer is exactly the fm7 microcomputer or specifically probably the FM new 7 which has this same device advice board I know this is a particularly interesting and unique architecture but enough talking and let's see it in action unfortunately it didn't come with any cables so we'll have to improvise the power cable is fine it's a standard PC cable and it expects 220 volts so we got that covered for the video out things get a bit more complicated the good news is that the display resolution is 640x200 so I think we can use a normal TV to display it as we saw earlier the fm7 has two video out connectors color and monochrome looking at the specs it looks like the color video is a digital RGB signal and the monochrome is a composite signal so let's start with that one because that should be easier to get at least something up and running the monochrome connector is a din 5 which is quite common it has a ground composite signal and both horizontal and vertical sync I'm hoping we can just tap into the composite signal directly but I'm not sure it includes the sync process or if we need to combine them the other thing I'm not sure about is whether this is a 50 hertz signal which is what you would expect for a pal display or a 60hz signal which is probably what it was in Japan since they use ntsc my displays here don't accept ntsc signals but there's no color in the monochrome signal so if it's just illuminance plus the sync that should probably work maybe however if it's 60 hertz we may need a special monitor to display it let's have a look at the oscilloscope to see what exactly it is I'm going to plug this din 5 connector here so I can clip the ground probe I have an easier access to the pins and it looks like the composite signal includes sync so that's great oh but it's 60 hertz they didn't change that at all from the Japanese release interesting here we have the video clock yep two megahertz like the syn frequency as the graphic CPU and I believe that's for the use with the light pan so you can keep track of exactly where in the screen it is I was about to start making a cable to display that composite signal when I remembered that A din 5 was pretty common video connector at the time the Commodore the ti-99 and even the Atari 8-bit all use that but unfortunately when it looked at the pin out it was slightly different however when I looked at it closely again I realized that the composite signal is in pin 3 which in the camera 64 carried the sound so we could use a Commodore 64 cable and plug in the audio RCA cable in the video input and that might just work foreign I mean the cable works and the Machine Works that is quite a relief because after seeing that board it would have been really intimidating trying to repair a non-working board not having seen a working one before okay but I'm not happy with just the monochrome signal can we get the full color output I said it was a digital RGB signal can we just feed that to the TV with an RGB input through the scar connector not quite when we talk about Display Devices with RGB inputs we usually refer to analog RGB that means it has three different inputs for the color channels rgmb any channel the signal will vary between 0 and the maximum voltage which is usually pretty low about 0.7 volts depending on how much of that color there is so something that has 50 red would have a voltage of 0.35 volts analog RGB usually only has a single sync signal for both horizontal and vertical sync with a digital RGB signal each color channel is either on which is probably 5 volts or off 0v so just those three signals we can only represent eight colors which is exactly the maximum number of colors on the fm7 by the way CGA is another famous video system that uses digital RGB in that case it has an additional signal intensity for a total of 16 different colors digital RGB signals also usually have separate horizontal and vertical signals like we're seeing here so because of all that we can't just fit it straight into the scar connector on the other hand it's not that difficult to convert the signal to something that the TV could accept we would need to add some resistors to the rgmb channels to lower the voltage into something that I can accept and we would need to combine the two sync signals into a single one and with that it might just work but you know what's even better than that not having to do it at all the fn7 digital RGB signal is a subset of the CGA signal and I already have a simple device that will convert a CJ signal into an analog RGB one that can be displayed on a TV this is a CGA to scart device and this particular one came from certa shop and I used it before in my amstrad PPC LCD enhancement a couple of years ago so in theory if I made a very simple adapter to be able to connect the fm7 color video out into here we should be able to see it displayed on the TV so let's give it a try the goal here is just to get something temporary to see if it works none of this is intended to be used in the long term I have plans for a much more permanent solution down the line so I'm not going to worry about making this pretty you've been warned this is just a matter of connecting the right lines on the din 8 connector to the correct lines in the dsub9 connector and how about that I just made the mistake I told you not to make when making video cables and I soldered the cables before putting the housing back well it's all just temporary so yeah that's kind of ugly but hopefully will work as long as we don't pull too much on those cables so I'll connect it to the CGA too scarred I'll also have to power the converter separately with an USB cable right away you can imagine that if we made a more permanent solution for this we could use the 12 volt Supply from the video connector instead of using an external source and with everything hopefully connected correctly there you go it seems to be working do we have color yes we do nice let's write a quick program to show the available colors okay I know not very exciting but it's definitely working so this is great two questions still remaining is why was this computer introduced in Spain and nowhere else and how come I had never heard of it to answer that we need to go back to 1975. Yes you heard that right 1975. I know I know the fm7 wasn't released in Japan until 1982 but bear with me for a second in 1975 the Spanish company Seko insa was created it was a collaboration between the Spanish Telephone Company some Spanish Banks and yes you guessed it correctly Fujitsu their objective was to create computers for the Spanish Market but at that time that meant bulky room-sized computers in this style of the PDP 11. however in 1984 they decided to enter the blooming personal computer Market bringing over the popular fm7 computer from Japan the idea was to present this computer to a program by the Spanish government to introduce computers in the classroom all over the country they wanted it to become the equivalent of the BBC in the UK or the Apple II in the US and given that goal the fm7 is actually a pretty good candidate good keyboard good technical capabilities lots of room for expansion and I believe it even has a master mode so the teacher could control other computers in the classroom unfortunately the government computer program never materialized and the fm7 lost its main objective I love all computer magazines and I have a bunch of Spanish ones from the early 80s so I did some researching and digging through them and I found what I think are some of the first ads for the second fm7 that means they did try to launch it into the market but it clearly wasn't able to compete with other personal computers at the time I have no idea how many units they actually sold but it couldn't have been that many given how clean this particular one was I wonder if it was ever used and maybe it just sat in a warehouse for years until it was discarded or given away so we have a pretty unique parallel architecture that frees the main CPU from doing Graphics tasks what kind of graphic operations are those exactly well I'm glad you asked because I was itching to dig into the technical manual and find out unfortunately all technical documentation I was able to find isn't Japanese and I'm afraid my Japanese is absolutely null but fortunately they used enough English words to understand what's going on it looks like we have a command to clear the screen which may sound not very exciting but that involves filling up a large section of Ram with zeros and it's pretty time consuming Heck on the amstrad CPC you can often see this screen being cleared with that typical closing Blind pattern so having something that does that while the CPU is off doing something else is definitely handy then we have commands to put characters on the screen and hold strings one to draw a line as I guessed earlier and I'm going to guess that chain is probably a sequence of lines paint is probably filling a whole area I'm not sure if that means using a painter's algorithm or if it's just a square fill but probably the most useful commands for games are the put blocks ones I think those take a data buffer in some dimensions and draw a rectangular area on the screen that's your typical Sprite drawing routine just happening on the other CPU that's actually a fantastic feature because 8-bit computers often spend 80 percent of the CPU power or more just moving Graphics around now that doesn't mean you're suddenly going to see games for the fm7 with amazing Graphics no one has seen before actually though probably somewhere similar to other games but the main CPU has time to do other things now so I would expect games to take full advantage of the fm7 architecture to have better AI game logic or even some Physics simulations which are things you just didn't usually see in other 8-bit games because the CPU just couldn't do it however there is a potential downside of having a separate Graphics coprocessor I imagine it gets a lot harder to try to do effects that rely on exact timings of certain things happening on the screen maybe related to interrupts or some other events these are often used in other computers to create unusual effects like screen ruptures and changing modes so I'm definitely curious to see if it's possible to do low level tricks like that on the fm7 I would love to check some of the best games on the system but I don't have a good way to feed the fm7 yet that will come in a later video it's also possible that the fm7 maybe never got really amazing games that exploited the architecture to the maximum so I'll have to look around in the meanwhile for any of you familiar with fm7 games which ones would you recommend that I check out let me know so I can make sure I try them out and showcase them in the next video when I started this video I was thinking that the most interesting part of this whole thing was that this computer was an unusual Spanish version of a Japanese computer but I ended up being much more interested in the unusual architecture of the fm7 itself independently of where it came from trying to get information about the fm7 has also been a very different experience from other computers most computers that I've covered are pretty well documented on the internet and all of the documentation is in a language that I can easily read on the other hand here we have a system that doesn't have nearly as much available documentation and most of it is in Japanese all I can say is thank you Google Translate There is a small but dedicated Community working on this platform I was able to connect with them through the Discord server and it's been an invaluable resource I'll leave a link in the description along with a few really useful technical sites that I used for This research that Community has also created some Modern expansions for the fm7 like a Communications card which will hopefully let us load programs quickly a sound card or a better video converter all of which sound like really interesting and useful projects unlike in the FM 7 enough that I'm hoping to be able to take it in the suitcase with me to go to the US and make a follow-up video sometimes showcasing some of the accessories and seeing if we can get some particularly impressive game on the fm7 I don't know if you'll fit in the suitcase though or if they'll let me go through security with this we'll find out see you next video foreign

Channel: Noel's Retro Lab

Views: 146,984

Keywords:

Id: 4LTMYocpE9M

Length: 24min 29sec (1469 seconds)

Published: Thu Aug 03 2023