EEVblog #746 - Sharp X68000 Retro Computer Teardown

[vlad777]

As a comment for mentioning the amount of 74 series logic used in that computer, have a look at this 386 mainboard from IBM:
It is a mix of ASICs (unter the metal cans), PLDs (PALs, MMI 72x7486) and a lot of 74 series logic. They did even make their own memory modules and ICs instead of using the standard SIMMs.

What is that bus ? It's not ISA.  It 's not VLB. Can't be PCI. Some of connectors look like 64 bit PCI?

[bktemp]

What is that bus ? It's not ISA.  It 's not VLB. Can't be PCI. Some of connectors look like 64 bit PCI?

I think it is MCA:
https://en.wikipedia.org/wiki/Micro_Channel_architecture

[Tothwolf]

What is that bus ? It's not ISA.  It 's not VLB. Can't be PCI. Some of connectors look like 64 bit PCI?

I think it is MCA:
https://en.wikipedia.org/wiki/Micro_Channel_architecture

It has been decades since I worked on one, but I'm pretty sure that is the main board from a 386 based PS/2 Model 80. These IBM PS/2 full tower style boards were huge, and even with an integrated parallel port, a serial port, and on-board VGA (up to 640x480, 16 colors), you really did need the slots. At a bare minimum I usually used at least two boards, an ESDI and/or SCSI controller and a network board (Western Digital or 3Com 10Base-2). If you wanted higher resolution VGA (1024x768, 16 colors; 256 colors if you added the additional 512K daughter board), the 8514/A adapter would take yet another slot. The same goes if you needed more than one serial port (we often did), and a dual serial port card would eat another slot. Even with all the MCA slots in these tower style PS/2 systems, there never seemed to be enough.

[Stonent]

The main reason IBM went with the 8088 was that it was peripherally compatible with Intel parts they had from the 8085 based IBM Datamaster and the 68000 had just hit the market in 1980. Motorola did not have the peripheral chips available in the kind quantities that IBM needed. They definitely wanted a CPU that could deal with more than 64k out of the box but didn't really see the PC as being worth a lot of invesyment. At one time they had even considered completely outsourcing the design to a third party but in the end decided just to outsource the OS.

[RupertGo]

And of course, when IBM did try to do a next-generation PC architecture with MCA and did apply lots of systems engineering and thought, the result was hideous. We produced one MCA_based peripheral, but the experience was so horrible and the market so puny it was very easy to walk away from. Even basic tasks like being able to install and test prototype device drivers were battles - the combination of IBM's tight control over what you could and couldn't do, and the shifting sands of OS/2, was just no fun at all. Quick, dirty and open won in the end.