Real first BIOS version in 5160 ?
Real first BIOS version in 5160 ?
By the way, I just stumbled across this bios file while searching for the one I mentioned above... The date stamp is 08/16/82 ... However, I haven't seen it before and I might think it is a modified version of another BIOS. It is fairly similar to the first XT BIOS revision, however it has some minor differences (chip number = 5000026 instead of 1501512, one byte in the code is different (line 937 in the PC XT systembios listings)).
What do you think is the origin of this dump, is it modified, or is it a beta?
That BIOS file is 8K in size. Only in the first 5160 BIOS version is one of the ROMs 8K in size, but the contents of that 8K ROM (U19) is part of BASIC, not the actual BIOS code itself (which is in the latter part of U18):
Memory map:
. = unused
b = ROM BASIC
R = ROM BIOS
------: 0---1---2---3---4---5---6---7---8---9---A---B---C---D---E---F---
0F0000: ........................bbbbbbbbbbbbbbbbbbbbbbbbbb bbbbbbRRRRRRRR
------: ........................|< U19 >|<----------- U18 ------------->|
It appears that the file is a trimmed version of a U18.
Searching the Internet for "5000026" reveals site
http://mess.toseciso.org/dumping:ibm_needed
And so according to the MESS project, there are four versions of the 5160 BIOS, not three:
Revision 1: 08/16/82 U18=5000026 / U19=5000027 <----------------- what you've found
Revision 2: 11/08/82 (known to be: U18=1501512 / U19=500027)
Revision 3: 01/10/86 (known to be: U18=62X0851 / U19=62X0854)
Revision 4: 05/09/86 (known to be: U18=59x7268 [EPROM] or 62x0890 [PROM] / U19=62x0819 [EPROM] or 68x4370 [PROM]
That is interesting. Most here would agree that an authorative source on PCs is Mueller's "Upgrading and Repairing PCs" book.
Mueller only lists 3 versions of the 5160 BIOS (the final 3 in the list of 4 above).
The BIOS date of 08/16/82 shows as being a BIOS date at:
1.
http://www.o3one.org/hwdocs/bios_doc/dosref22.html
2.
http://www.brl.ntt.co.jp/people/takehiko/interrupt/INTERRUP_C.txt
And the book, "PC-based instrumentation and Control", has a page showing the major ROM releases. It indicates that the "08/16/82" BIOS is the "original" one used in the 5160. Odd though that it doesn't list the 05/09/86 version.
And so I'm convinced now that there are 4 versions of the 5160 BIOS. However, noting that the 5000026 chip was replaced by the 1501512 in very late 1982, and that the 5160 was released in March 1983, a question is, did the 5000026 chip make it into released 5160s? Maybe it didn't, and that is why Mueller doesn't list it.
, one byte in the code is different (line 937 in the PC XT systembios listings)).
The BIOS supports a feature where test code can be loaded via the keyboard port. It's used by IBM during manufacturing, and is referred to as 'manufacturing test mode'. The byte (of functional code) that is changed between the 08/16/82 and 11/08/82 BIOS versions is in a block of code that gets called if the 'manufacturing test mode' is active, specifically code that sets up the timer chip to initiate the blinking of a LED.
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