Reading IBM PC XT 5160 BIOS chip \ VOGONS

Reading IBM PC XT 5160 BIOS chip

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First post, by A. Fig Lee

Posted on 2025-07-28, 12:23

A. Fig Lee Offline

Rank Newbie

Rank: Newbie
Posts: 5
Joined: 2023-09-04, 23:02

Hello everyone, my XT is hangs on some programs, like Norton Commander, so I decided to check hardware and started with BIOS. I identified my chips as latest XT revision masked ROM chips 62X0890-U18 and his friend.
I tried to read it using TL-866 II chinese clone and no success. Used 27C256 or 28C256 pinout - in both cases it showed pin 1 does not match.
Is it possible to read those chips with TL-866? Did I choose wrong chip type? Hopefully I did not destroy them..
Thank you for reading my suspense story

Reply 1 of 2, by maxtherabbit

Posted on 2025-07-28, 12:50

maxtherabbit Offline

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Posts: 3743
Joined: 2018-10-30, 16:36
Location: Richmond, VA

Pin 1 on a 27C256 pinout is Vpp. This will be a N/C pin on a mask ROM. You can just tell Xgpro to ignore the error and continue. Do not use the 28C256 pinout.

Reply 2 of 2, by A. Fig Lee

Posted on 2025-07-28, 13:35

A. Fig Lee Offline

Rank Newbie

Rank: Newbie
Posts: 5
Joined: 2023-09-04, 23:02

maxtherabbit wrote on 2025-07-28, 12:50:

Pin 1 on a 27C256 pinout is Vpp. This will be a N/C pin on a mask ROM. You can just tell Xgpro to ignore the error and continue. Do not use the 28C256 pinout.

Thank you! Will try

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