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Why does EMS suck on my 286?

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Reply 161 of 167, by maxtherabbit

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Scali wrote:

You know, there's a way to offer help, useful tips and constructive criticism without being a pompous egotistical ass.

I'm guessing this is not directed at me 😎

Reply 162 of 167, by bakemono

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Reworking the card to serve odd bytes only, nice save.

And now your ROM code can execute faster too. Any benchmarks? 😉

yet another retro game on itch: https://90soft90.itch.io/super-wild-war-22

Reply 163 of 167, by kjliew

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I have to say that your persistence and hardware skills are something to admire. And kudos 😀 to your success in search of harmony for SCSI and EMS addons for 286!

Though I do have the knowledge to read schematics and understand digital logics, I have since groomed as a software guy. Back then in the college days, I even self-learned Protel PCB with auto-routing but was lacking the resources of accessing to hobbyist PCB build facilities. I had only done 2 PCBs in my life, and that was with primitive, laborious process of using marker pens, toxic chemical solution and manual drilling. (So then I said forget it 😵 ) I am OK with soldering which I still do today if needed. If I were to put in your situation, then I would have gone with writing the TSR to shadow the SCSI ROM.

I remember the pain of having early 286 without hardware EMS as my 1st PC as a kid was exactly such poor 286, in those days when there was no internet, no electronics superstores and computer sales person would knock on the door to make a deal. And I do realize the importance of EMS for 286 being the transitional gap between 8086 software and true protected-mode software for 386.

Hope you finally would get the design right and then the ROM on the SCSI can be disabled to use the 16-bit ROM card entirely.

Reply 164 of 167, by maxtherabbit

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bakemono wrote:

Reworking the card to serve odd bytes only, nice save.

And now your ROM code can execute faster too. Any benchmarks? 😉

Yes, it actually did make a small but measurable difference.

8-bit ROM access:

8bit ROM.jpg
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16-bit ROM access:

16bit ROM.jpg
Filename
16bit ROM.jpg
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1.95 MiB
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181 views
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Fair use/fair dealing exception

Reply 165 of 167, by maxtherabbit

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kjliew wrote:
I have to say that your persistence and hardware skills are something to admire. And kudos :) to your success in search of harmo […]
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I have to say that your persistence and hardware skills are something to admire. And kudos 😀 to your success in search of harmony for SCSI and EMS addons for 286!

Though I do have the knowledge to read schematics and understand digital logics, I have since groomed as a software guy. Back then in the college days, I even self-learned Protel PCB with auto-routing but was lacking the resources of accessing to hobbyist PCB build facilities. I had only done 2 PCBs in my life, and that was with primitive, laborious process of using marker pens, toxic chemical solution and manual drilling. (So then I said forget it 😵 ) I am OK with soldering which I still do today if needed. If I were to put in your situation, then I would have gone with writing the TSR to shadow the SCSI ROM.

I remember the pain of having early 286 without hardware EMS as my 1st PC as a kid was exactly such poor 286, in those days when there was no internet, no electronics superstores and computer sales person would knock on the door to make a deal. And I do realize the importance of EMS for 286 being the transitional gap between 8086 software and true protected-mode software for 386.

Hope you finally would get the design right and then the ROM on the SCSI can be disabled to use the 16-bit ROM card entirely.

Thank you

I've already corrected the schematic and PCB, I'll probably get a revised board made next time I do an order. It will get done up right at some point, but I'm just happy the system is working properly for now.

Reply 166 of 167, by pentiumspeed

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If you find a way to make a software to shadow these roms including bios into upper memory. This will increase much more and does not use up the memory either as the address are re-directed to the memory space.

Cheers,

Great Northern aka Canada.

Reply 167 of 167, by maxtherabbit

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pentiumspeed wrote:

If you find a way to make a software to shadow these roms including bios into upper memory. This will increase much more and does not use up the memory either as the address are re-directed to the memory space.

Cheers,

there is no upper memory on this system 🤣