Looks fun. I didn't know that this existed.

I've seen that before and thought about it. If it had been XT instead I would have been all over it. Instead I decided to build Sergey Malinov's 8088 Xi project which I am in the process of doing.

Why are there two DIN connectors? Are both for keyboards? I really like when there are things like this. I would also like to build a computer from pieces but my skills aren't that good.

I'd buy one right now, but I'm not sure if one could play lemmings on an 8080 and with 256k of ram?
I think is needs a 286 and 512k of ram? If anyone knows if lemming can be played on such a setup let me know and I'll nab one up.

markot wrote:

Why are there two DIN connectors? Are both for keyboards? I really like when there are things like this. I would also like to build a computer from pieces but my skills aren't that good.

The webpage states, that it is a clone of the original IBM Model 5150 motherboard.
Searching for pictures of the original 5150 machine, I have come across this.
As seen on the picture, it must be a casette port.

http://classiccmp.org/dunfield/pc/index.htm#pc
http://classiccmp.org/dunfield/pc/h/pc5150bk.jpg

thing to note, the slot spacing is not standard isa slot spacing so you cant just throw this into any case!

also, it uses a fixed crystal so putting in a faster cpu wont get you that speed, like using the 8mhz versions etc.

Id love to build one but dont have a proper case for it, so will probably build Segey's xi 8088

Really cool, but i would prefer Sergey's Xi8088.

In fact i would only consider to buy Sergey's Xi project if it could run 8086/V30 instead.

Good point, didn't notice that the ISA slot spacing was different compared to newer motherboards. When did the motherboards start to have standardized spacing of these slots?

I wish there were some DIY 486 motherboard, but have not found any.

The real benefit compared to Xi8088 is that this apparantly comes with EVERYTHING.

It took me ages to track down some of the more obscure parts for the Xi8088.

keenerb wrote:

The real benefit compared to Xi8088 is that this apparantly comes with EVERYTHING.

It took me ages to track down some of the more obscure parts for the Xi8088.

Umm, what exactly? A couple of quick trips to ebay and aliexpress landed me with almost everything. The only parts that I don't have are the ones I haven't even searched yet (on purpose, lacking funds...)

stamasd wrote:

keenerb wrote:

The real benefit compared to Xi8088 is that this apparantly comes with EVERYTHING.

It took me ages to track down some of the more obscure parts for the Xi8088.

Umm, what exactly? A couple of quick trips to ebay and aliexpress landed me with almost everything. The only parts that I don't have are the ones I haven't even searched yet (on purpose, lacking funds...)

Yeah, I ended up with like 8 ebay orders, a Jameco order, a Mouser order, and a Digikey order to get all the pieces I needed.

I can't remember specifically what it was I had a hard time finding. I do recall nobody having the 5-pin resistor array in stock.

I struggled with finding the right parts as well; the BOM for xi8088 had a lot of items that were no longer carried or ones where I had to figure out if I needed the LS, ALS, AHCT, HCT, etc. parts, which isn't easy considering I have no idea what any of that means...

keenerb wrote:

I struggled with finding the right parts as well; the BOM for xi8088 had a lot of items that were no longer carried or ones where I had to figure out if I needed the LS, ALS, AHCT, HCT, etc. parts, which isn't easy considering I have no idea what any of that means...

74S, LS, ALS and F are all bipolar (TTL) parts; 74S are a bit more power hungry that the others, but are faster. Speed goes S>ALS>LS; 74F are about the same as ALS (similar technology, Fairchild's alternative to LS/ALS)

74HC/HCT, AC/ACT, AHC/AHCT are CMOS parts (the T at the end means "TTL compatible"; those with T can be mixed in the same circuit with bipolar parts, those without it can't - in this project don't use HC, AC or AHC parts or you'll run into trouble). Speed is AHCT>ACT>HCT; HC/HCT are about the same speed as LS if not a bit slower, the others are between LS and ALS.

Though for a low-frequency application as a XT motherboard speed doesn't really matter, you can use any of the above families more or less freely. The speed differences only matter at frequencies above 30-40MHz.

I for one prefer to use 74F parts anywhere I can. They have good speed, decent power usage and are not static-sensitive like the CMOS parts.

See https://en.wikipedia.org/wiki/Logic_family for a brief overview.

As for the resistor arrays, they are convenient but not indispensable. They can be replaced by discrete subminiature individual resistors with the leads on one end soldered together. Works the same but looks messier.

markot wrote:

Good point, didn't notice that the ISA slot spacing was different compared to newer motherboards. When did the motherboards start to have standardized spacing of these slots?

I wish there were some DIY 486 motherboard, but have not found any.

The number of slots changed from the IBM PC 5150 (5) to the PC/XT 5160 (the more familiar 8 ).

stamasd wrote:

74S, LS, ALS and F are all bipolar (TTL) parts; 74S are a bit more power hungry that the others, but are faster. Speed goes S>AL […]
Show full quote

keenerb wrote:

I struggled with finding the right parts as well; the BOM for xi8088 had a lot of items that were no longer carried or ones where I had to figure out if I needed the LS, ALS, AHCT, HCT, etc. parts, which isn't easy considering I have no idea what any of that means...

74S, LS, ALS and F are all bipolar (TTL) parts; 74S are a bit more power hungry that the others, but are faster. Speed goes S>ALS>LS; 74F are about the same as ALS (similar technology, Fairchild's alternative to LS/ALS)

74HC/HCT, AC/ACT, AHC/AHCT are CMOS parts (the T at the end means "TTL compatible"; those with T can be mixed in the same circuit with bipolar parts, those without it can't - in this project don't use HC, AC or AHC parts or you'll run into trouble). Speed is AHCT>ACT>HCT; HC/HCT are about the same speed as LS if not a bit slower, the others are between LS and ALS.

Though for a low-frequency application as a XT motherboard speed doesn't really matter, you can use any of the above families more or less freely. The speed differences only matter at frequencies above 30-40MHz.

I for one prefer to use 74F parts anywhere I can. They have good speed, decent power usage and are not static-sensitive like the CMOS parts.

See https://en.wikipedia.org/wiki/Logic_family for a brief overview.

As for the resistor arrays, they are convenient but not indispensable. They can be replaced by discrete subminiature individual resistors with the leads on one end soldered together. Works the same but looks messier.

Well you gave me a lot to look over here. My mouser order includes als, ls, ahct, and a few ahc. If my understanding is correct, those AHC parts wouldn't work with the ALS/LS parts? Or might if they're in different circuits... What's the worst that would happen if I mixed the two types?

keenerb wrote:

Well you gave me a lot to look over here. My mouser order includes als, ls, ahct, and a few ahc. If my understanding is correct, those AHC parts wouldn't work with the ALS/LS parts? Or might if they're in different circuits... What's the worst that would happen if I mixed the two types?

mostly it depends where in the circuit your mixing ALS + AHC parts. its about voltage levels and how the chips that connect see a HI signal from a LO signal etc.

keenerb wrote:

Well you gave me a lot to look over here. My mouser order includes als, ls, ahct, and a few ahc. If my understanding is correct, those AHC parts wouldn't work with the ALS/LS parts? Or might if they're in different circuits... What's the worst that would happen if I mixed the two types?

The worst that can happen is that an AHC gate that receives input from a TTL gate may not interpret correctly the input. It will see the "0" levels correctly, but it may see the "1" levels as indefinite because it expects that a "1" is between 4.5 and 5V, whereas a TTL gate outputs a "1" anywhere between 2.4 and 5V. This problem is fixed in "T" parts which can correctly interpret "1" TTL levels. What happens otherwise is you get incorrect address decoding, incorrect data transmission etc. depending on where in the circuit the AHC parts are.

There's one saving grace, may or may not apply to you depending on where the AHC parts are and where they get the input from. If you use them where they get input from other CMOS parts (HCT, ACT or AHCT) there won't be a problem because the CMOS gates output is compatible with other CMOS gates' input regardless of which CMOS family they belong to.

In other words:

TTL-> TTL is OK
TTL -> CMOS(T) is OK
TTL -> CMOS (non-T) is not OK
CMOS(any) -> CMOS(any) (e.g. ACT ->AC)is OK
CMOS(any) -> TTL is OK (provided that you don't drive more than 2 or 3 TTL inputs from any one CMOS output, because the CMOS output has a significantly lower current capacity that a TTL output)

Will it run 8080 MPH?