Comparing Intel 8088 CPUs
Comparing Intel 8088 CPUs
the chip that made Intel
On the 12th of August in 1981, IBM unveiled the PC model 5150 in the ballroom of the Waldorf Astoria hotel in New York City. The 5150 had 64K RAM (or 128K), monochrome display adapter (or CGA), the best computer keyboard ever made (the Model F), a programmable-frequency square wave, two 360k 5.25 inch disk drives (or one or none), cassette tape recorder port, five 8 bit ISA expansion slots, and options for: a hard disk drive, an expansion chassis, serial and parallel ports. The CPU for this computer was the Intel 8088 at 4.77MHz. Many people correctly point out that the 8088 wasn’t the most powerful CPU of the day. That was the 8086. Many people also point out that the IBM PC wasn’t the most powerful computer at launch. This too is correct. The IBM PC was, however, the most powerful computer that the average person could actually purchase. The competitors to it were machines like the Commodore VIC-20, the Apple 2, the CoCo, the Atari 800, the ZX81, and S100 bus machines. These were all purely 8 bit machines with either the MOS 6502 or the Zilog Z80, and these all had lower RAM. Unless a person were purchasing an Apple 2 or an S100 bus computer, he/she would also have far less expandability. It is worth noting, however, that were one looking specifically for gaming capability some of these other computers would have been a better fit at the time of the PC’s launch.
IBM’s choice of the 8088 was due in large part to the 8080 and Z80 having been widely used in other home micros. Automatic source code translation tools were available to software developers, and these would handle most of the work of porting applications to the 8088. Having a large software library available for consumers at launch is a big deal. People don’t want or need a computer that can do nothing for them. The 8088 was also compatible with existing support and peripheral ICs that were rather inexpensive compared to their 16 bit counterparts. Those 8 bit ICs were also well known by engineers which helped cut the development time required for the PC.
The base model IBM PC cost $1565 in 1981 which is roughly $5131 in 2022 if we adjust for inflation. At its highest launch configuration with a printer and color monitor, a person would have had to pay roughly $4700. To put that into perspective, the Honda Accord of 1981 had an MSRP of $6918 which would be about $22680 in 2022. So, the IBM PC in its day had roughly the kind of pricing we expect from Apple (think Mac Studio or Mac Pro) in the present day. It was extremely expensive, but it was attainable. People held on to computers quite a bit longer in the 80s, and IBM PCs were useful until the early to mid 90s.
The IBM PC sold extremely well, where at its peak one IBM PC sold each minute of each business day. This is likely due to the PC having the IBM name as well as an 80 column screen, which made it far more useful in business and office applications than its competitors. Additionally, when comparing the build quality of the IBM PC to other computers of the day, it was exceptional. The build quality of the 5150 was so high that 5150s were still in use in commercial, industrial, and government deployments well into the 90s.
The Intel 8088, released in 1979 (one year after the 8086), is among the most important computer processors ever made. The success of the PC was the success of the 8088. The success of the 8088 was the rise to dominance of the x86 architecture.
The 8088 is an 8086 but with an 8 bit external data bus instead of the 8086’s 16 bit data bus. This means that the 8088 requires 2 bus cycles to read or write 16 bit data. It’s slower. The 8086 could do the same task in a single cycle. Otherwise, the 8088 has 16 bit registers, a 16 bit internal data bus, and a 20 bit address bus. The 8088 can address up to 1 MB of RAM via segmentation. It can address 64k, and it can then set the segment register, do another 64k and then update the segment register again. As far as clock speeds go, the 8088 wasn’t a slouch in its day. It could achieve 4.77MHz in the original IBM PC. The 8088 can do between 0.33 MIPS and 0.75 MIPS. The 8088 compatible NEC V20 (and similar chips) could achieve higher performance.
The 8088 was initially fabricated with Intel’s depletion-load silicon gate NMOS called HMOS (High density, short channel MOS) and a 3 micron process. Interconnects are done with a single metal layer on top of the silicon. Later versions of the 8088 were made with CMOS that borrowed from HMOS, and these were on a 1.5 micron process. The 8088 was created of 29000 transistors.
The 8088 was released in a 40 pin dual in-line package (DIP) and priced at $124.80 in 1979 dollars (roughly $512.90 in 2022). The price dropped to $31.90 by July of 1981, or $20 per chip in quantities of 100. In July of 1981 the plastic 8088 (P8088 series) sold for $14.10 per chip in quantities of 100 (roughly $46.23 in 2022). Amazingly, the 8088 wasn’t discontinued until 1998 where the last price I could find was $5.34 (which is roughly $9.76 in 2022), but it could have been cheaper. I can only report what I was able to find.
I do not own a 5150, but I do have a turbo XT. I also happen to own several 8088 class chips from different manufacturers: AMD p8088, Intel p8088, Fujitsu 8088-2, NEC V20. I benchmarked these in my Turbo XT.
AMD 8088, 1981
So, an AMD 8088 manufactured in 1981 scores:
4 @ 4.77MHz
6 @ 7.16 MHz
8 @ 9.55 MHz
Fujitsu 8088-2, 1986
The Fujitsu 8088-2 manufactured in 1986 scores:
4 @ 4.77MHz
6 @ 7.16MHz
8 @ 9.55MHz
NEC V20, 1984
The NEC V20 manufactured in 1984 scores:
6 @ 4.77MHz
8 @ 7.16MHz
11 @ 9.55MHz
Intel 8088, 1998
The Intel 8088 manufactured in 1998 scores:
4 @ 4.77MHz
6 @ 7.16 MHz
8 @ 9.55MHz
I was a little surprised to see that the 8088-2 didn’t score higher than the 8088s by any significant margin, but I was completely unsurprised to see the NEC beat the other three. It’s worth noting that the AMD and Intel chips were not rated for 7.16 or 9.55 clock speeds, and I am unsure of how they would have performed outside of a very quick benchmark at speeds above 4.77MHz. Of course, it would be good to test the Fujitsu and NEC CPUs with real world loads. I will have to handle that in another post at some point.
I would add that the 8088 had an 8-bit data bus. The standard DRAM chips at that time were 16K x 1 bits. A minimum system was 16K, with 8 chip increments. The 8086, with a 16-bit data bus, required 16 chips minimum and 16 chips for any additional bank of RAM. Soon after shipping, 64K x 1 bit DRAM chips became available, so the 64K byte system required only 8 chips, where an 8086 system required 16 chips. The minimum system for an 8086 using 64K DRAM chips was 128K bytes.