I’ve come back to my parents to visit them again and have found some more interesting hardware hiding away including two modems and an old PC clone belonging to my younger brother. Unfortunately for my Dad, internet providers aren’t very good at providing good service to rural areas, he is too far to get any kind of ADSL service. This had meant that for much longer than others he had to rely on dial-up until alternatives became available.
I forgot to bring my own camera, but was able to borrow my mothers, which whilst it has a higher pixel count it didn’t seem to do as well in the shots I took. I’ve had to adjust these images for brightness particularly.
This Dynalink modem is a pretty basic USB modem, I unfortunately couldn’t open it for any internal shots but it’s probably not very interesting as it’s small and almost certainly a software modem of some type. Dad used it for some time and had problems with drop-outs so we went about getting a better modem.
So we got this modem, a SmartSwan Turbo which much like my own modem is a proper self-contained serial modem you can use without drivers. This one was bought a little later (sometime around 2003 I don’t really remember) and did perform quite a bit better than the Dynalink modem. Unfortunately given the line quality and distance to the exchange there were still some issues, mostly speed and the very occasional drop-out.
I was able to take this modem apart quite easily, just four screws on the bottom. Here is an overview of the main board, you’ll notice that it is an Ambient chipset and is a voice modem (although we didn’t use that feature). Unlike my modem this one does have a line transformer and a DIP mask ROM chip for the firmware. It also has some similar features, like what appears to be a rectifier chip in the modem front end. Interestingly there is a 74 series logic chip (surface mount) towards the lower right of the board, something that has become unusual in modern equipment.
Here are the two primary chips up close, I believe the left one is the main DSP doing most of the grunt work for the modem, the one on the right looks like the serial interface. I found it difficult to find the data sheets for these chips as Ambient was formerly Cirrus Logic and now is a part of Intel. The chips were made late in 2002 so Dad probably bought this about the same time I got my modem.
The front end has fewer protection devices and simpler circuitry with fewer passive components. It may be using an older design with some updates. Not being an analog circuit (or any kind of circuit) guru I can’t really tell. Next up I took some photos of an old XT PC clone, a Canon A-200 20HD. My younger brother bought this machine for basically nothing, which is extremely lucky considering how hard they are to find in working condition. I found an article on google books here that reviewed the machine when it first came out, you will need to scroll up to read the whole article.
The machine in all its glory! It is lucky enough to still have the Canon branded monitor and keyboard with it, everything seems to have yellowed quite badly, although at least it’s uniform. The keyboard is still nice to type on and doesn’t seem to have any defects, although it does have the older XT style layout. The keyboard is compatible with the IBM XT class machines so it is possible to use it on another machine or replace this one if needed. The monitor is a pretty basic green phosphor monochrome monitor that seems to have been treated quite well. There doesn’t seem to be any burn-in and it is still quite bright and easy to read.
Here I’ve pulled the lid off to expose the internals, you can see a Canon 360k 5.25 inch floppy drive and a 20Mb NEC hard disk that has unfortunately stopped spinning. Fortunately I have some MS-DOS 4.01 floppies that allowed me to boot the machine, but it took ages to get to the normal prompt. In the expansion slots you can see a memory expansion card, the graphic card and hard disk controller. The floppy, serial and a parallel controller are integrated on the main board which means there are some slots free for further expansion. The main processor is an 8086 at 4.77Mhz which can be at times significantly faster than the 8088 found in IBM PCs at the time. This is because the 8086 has a 16 bit data bus (as opposed to 8) and could move data and instructions faster over the bus.
Here is the graphics adapter, interestingly it is not a Canon part but is made by Twinhead judging by the logo on the board. I can’t tell if it is Hercules compatible but it most certainly is compatible with MDA cards. I didn’t get any clues from the chips as many are 74 series, memory or other generic chips.
This is a memory expansion card, these cards frequently have a few different devices on them as well. In this case what appears to be a real-time clock and a 25 pin RS-232 port. This card has 6 x 64Kb banks of extra memory (384Kb made with 4164 DRAM chips) which would have required a special driver for the machine to gain access to it. The machine finds 320Kb of ram, but this is most likely the memory on the motherboard.
Finally here is the hard disk controller, a Western Digital device much like a later 16 bit one I have in my spare parts box. This one is only 8 bit and has more parts on the board, one with an old school Toshiba logo. Controllers such as this one were very common in all kinds of PCs of the time. Unfortunately the hard disk doesn’t seem to work any more, perhaps it’s time this machine got an emulated hard disk of some type.
Recent Comments