Why do have some of the 8088 motherboards having a dubble din keyboard connection??
Is this to align it with the hole of the case, that some cases having it misplaced? Or having it an other function?
And iam looking for an 8088 processor, how do i know it can do 10mhz?? How can i see this?
~ At least it can do black and white~
One is for the cassette interface (they were cheaper than floppy disk drives).
Wow....I took apart a LOT of AT machines but I never came across this feature O.0
The original IBM PC 5150 had a casette port. DOS wasn't available on cassette so all you had access to when booting from casette was BASIC in the machines ROM.
By the time the XT came around this feature was dropped as pretty much nobody used the PC without DOS.
Which is why you'll never see this on AT machines 😉 only original PC form factor boards will have it, usually running an 8088 processor.
If you are squeamish, don't prod the beach rubble.
wrote:The original IBM PC 5150 had a casette port. DOS wasn't available on cassette so all you had access to when booting from casette was BASIC in the machines ROM.
By the time the XT came around this feature was dropped as pretty much nobody used the PC without DOS.Which is why you'll never see this on AT machines 😉 only original PC form factor boards will have it, usually running an 8088 processor.
Ah, thanks for clearing this out! I forgot to mention I did also take apart a lot of XT ones (even IBM ones) and just never seen one. This was all in 2002-2003 when these computers were considered to be just old and unwanted trash by everyone but me 🤣
Robin4 what are you actually planning to do with an 8088?
The picture you linked looks like an original IBM PC motherboard.
Note that the IBM PC has a different form factor to AT clone machines. Not only does it have the two DIN ports on the back but the ISA slots are actually further apart - so if you try to stick a 5150 PC motherboard into an AT case none of the expansion slots will line up with the brackets in the case.
Also, the PC used a different keyboard to AT. The connector looks the same but the signals are different, so not just any AT keyboard will work.
If you have your heart set on an 8088 either track down an AT form factor board, or try to find a complete IBM 5150 PC or 5160 XT machine, or equivalent clone. Just buying a motherboard like the one you linked won't do you much good.
The original PC and many clones also don't support IDE hard disks, if you intend to install a hard drive in the machine you will want to look at the XT-IDE project
If you are squeamish, don't prod the beach rubble.
wrote:Wow....I took apart a LOT of AT machines but I never came across this feature O.0
Yeah me too, thats why i made this thread. I havent seen before in my whole live on those motherboards.
~ At least it can do black and white~
Clue #2 is the slots. there is only FIVE and they are spaced wider than "normal". Only the original XT has slots like that. But yea, floppies killed the cassette for data storage.
On a side note, people have made a VHS data interface card, and it would backup your hard drive to a VHS.
I've never seen one in person, but things like that existed. Computers used to be FUN and homemade. There was a place to explore and create and thats gone now. 🙁
It is a mistake to think you can solve any major problems just with potatoes.
I also want to know. Why does old motherboards has 2 biosses ( and mostly there are empty sockets near them) What are those empty sockets for?
~ At least it can do black and white~
Some early motherboards with 16-bit external bus had 2 BIOS chips, one for even bytes of the ROM contents and one for odd bytes. I believe this was simply because the ROM chips were 8 bits wide so they were configured in a parallel fashion, to give 16 bits.
As for missing sockets, could be anything. Its hard to give details without seeing a picture.
A lot of things were socketed back in the early days as it was more economical to repair board rather than just throw them out, and repairs are easier if the faulty part is socketed rather than soldered on. If you're buying second hand boards its possible that someone has stolen the chips off it at some point. Often the sockets are just for some sort of upgrade and the board will work fine without it.
So if they are have 16-bit external bus they could use an 8086 on it?
Its very hard to find a good working XT motherboard nowdays.. And i only can find them on ebay.. here in the netherlands you wont find them anymore.. They throw them all away..
~ At least it can do black and white~
So if they are have 16-bit external bus they could use an 8086 on it?
I think we're on different wavelengths here. The presence of more than one ROM chip doesn't indicate a 16-bit external bus.
As far as I know the IBM 8088 machines all had a single BIOS chip. You might be looking at a different ROM chip. The PC, XT and AT had BASIC in ROM, which wouldn't fit onto a single chip with the BIOS.
The chip you are looking at might not necessarily be a ROM chip. There were a lot of discrete control chips in those old boards, which slowly got integrated into fewer and fewer chips.
If you are squeamish, don't prod the beach rubble.
wrote:I also want to know. Why does old motherboards has 2 biosses ( and mostly there are empty sockets near them) What are those empty sockets for?
flash memory only had so much capacity. usually there were little windows that you can see inside the chip. These required a "blacklight" of sorts to erase them for re-programming.
So basically instead of 1 expensive chip, they made 2, 4 bit chips and put them in parallel. or 2 8's, whatever. most 286 and older computers used multiple chips for the bios.
As for the open sockets, the original XT's had the option of not using dos but instead dump you immediately into basic programming mode. I mean basic the programming language.
I've never seen anyone get the basic bios chips. But I do know they existed.
It is a mistake to think you can solve any major problems just with potatoes.
This is a good resource for info about the old PC/XT/AT
http://www.vintage-computer.com/vcforum/forum … -PCs-and-Clones
Particularly the sticky topics at the top of the page.
Regarding the IBM 5150 PC:
All BIOS versions are 40KB in size. Chip U33 has the 8KB of BIOS. Chips U29-U32 (8KB each) hold BASIC.
There are 5 chips for BIOS but only one of them is required as the rest are just BASIC.
Regarding the 5160 XT
ROM U18 = 32K chip labeled with IBM part number of 5000026
ROM U19 = 8K chip labeled with IBM part number of 5000027 (reused in the next BIOS - dated 11/08/82)U18 contains the actual BIOS plus part of BASIC. U19 contains the remainder of BASIC.
Regarding the IBM AT:
ROM U27 = 32K chip
ROM U47 = 32K chip
The AT had the even/odd BIOS described above, it appears that BASIC was included in these two chips.
IBM had to include BASIC in every PC/XT/AT sold as part of their licensing agreement with Microsoft.
If you are squeamish, don't prod the beach rubble.
