Sierra AGI Tandy 1000 System Speed Benchmarks

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Nerdly Pleasures (Great Hierophant)

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Published on June 3, 2025 12:56:06 PM ● Video Link: https://www.youtube.com/watch?v=8fSNgNfHAUk

Game:

King's Quest I (1984)

Duration: 0:00

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I have often asked myself, what is an acceptable speed to run Sierra's AGI engine games on their optimal original hardware setup. That would be using a Tandy 1000 or an IBM PCjr. Tandy 1000s run a range of CPU types and speeds, from a 4.77MHz 8088 to a 10MHz 80286.

In order to run a "benchmark", I needed to find a portion of one of the games that was sensitive to system speeds and able to be replicated. I decided to record Sir Graham walking across the right screen of King Edward's Castle in King's Quest I: Quest for the Crown. I start from just off the screen and just press the right arrow, which makes Graham walk until he touches an object. To get a clear, safe and complete path I have him walk behind the castle and the tree.

KQ1 has three speed options, Slow, Normal & Fast. Other AGI games have a Fastest option, but that is equivalent to Fast in this game. I set Graham to Fast because that is the only mode which is not throttled to the system timer. The Slow and Normal speeds rely on the system timer to give a baseline speed regardless of the CPU speed, Fast/Fastest lets the animation move as fast as the system can drive it. I start with Normal Speed as a baseline because it is not affected by system speed. Then we will compare the Fast Speed on the various CPUs and systems to see how fast they are relative to Normal Speed.

AGI games demand significant system resources when objects other than the player animate or can be animated on the screen. The first screen of King's Quest is fairly taxing for AGI games, the three flags and two alligators animate. Screens with fewer/no animations will result in your character moving across them much more quickly, even with slower CPUs.

I time the recording so it starts as soon as the screen finishes drawing and end it when the animation for that screen stops, which means the engine is busy loading the next screen. Loading times are highly dependent on the media, drive and interface used. I have added in two black frames to indicate roughly where one benchmark ends and another begins. I have not included any loading times because they are highly variable depending on the media used (floppy vs. hard disk vs. CF card.)

I included "official" or common upgrades where possible. The Tandy 1000 SX came with an Intel or AMD 8088 CPU running at 7.16MHz from the factory, the fast mode, but the CPU was socketed and many owners upgraded to an NEC V20 for slightly improved performance. The SX could be set to 4.77MHz, the slow mode, on bootup or via a MODE command in DOS for compatibility with titles that only ran properly at the original IBM PC, XT and Tandy 1000 speeds. The Tandy 1000 EX and HX also run their 8088s at 7.16MHz/4.77MHz. The earlier Tandy 1000, 1000A and 1000HD only run their 8088s at 4.77MHz. All 8088 Tandy 1000s come with socketed CPUs, so they can easily be upgraded to the V20.

The IBM PCjr. also uses a 4.77MHz 8088, and most of them are socketed, making the V20 upgrade easy. When the PCjr. runs games with 256KiB or more memory and a memory manager loaded, which all the AGI DOS-installable games require, the system is is equivalent to a Tandy 1000 at the same speed. Most AGI game versions will automatically load their own memory manager on the PCjr.

Tandy marketed and sold the 286 Express upgrade card for the Tandy 1000, 1000A and 1000HD and 1000 SX. The 286 Express an ISA card with an Intel or AMD 80286 CPU which runs at 7.16MHz. Because the 286, which has a 16-bit data bus, has to access mainboard memory over an 8-bit ISA bus, the card comes with 8KiB of cache to avoid slow memory accesses whenever possible. This cache can be turned off if there is a compatibility issue, but that severely impacts the system's performance.

Some Tandy 1000s came with 8086s, which are 16-bit bus versions of the 8-bit 8088. The SL & SL/2 run their 8086s at 8MHz/4MHz and the RL run its 8086 at 9.44MHz/4.77MHz. The SL and SL/2 can be easily upgraded to an NEC V30 CPU for a similar performance boost that comes when you upgrade an 8088 to a V20. The RL and RL-HD use soldered PLCC-package 8086s and PLCC V30s are very rare.

Tandy sold several systems with 286s, the TX, TL, TL/2, TL/3 & RLX. The TX, TL & TL/2 use an 8MHz 286 and can slow it down to 4MHz. TL/3s and RLX run at 10MHz/5MHz but RLXs do not have the original Tandy graphics adapter, they have VGA built-in. Only the versions of AGI games with interpreter v2.917 or higher can run EGA/VGA graphics with Tandy sound properly. The PLCC 286s in the TX & TLs are socketed and can be replaced with 286 to 486 upgrades, but these were rare.

The results in order from slowest to fastest:

0:00 - Normal Speed
0:15 - Tandy 1000 SX 80286 7.16MHz 286 Express, Cache Off
0:30 - Tandy 1000 SX 8088 4.77MHz
0:45 - Tandy 1000 SX V20 4.77MHz
0:59 - Tandy 1000 SX 8088 7.16MHz
1:11 - Tandy 1000 SX V20 7.16MHz
1:22 - Tandy 1000 TL 80286 4MHz
1:32 - Tandy 1000 SX 80286 7.16MHz 286 Express, Cache On
1:36 - Tandy 1000 TL 80286 8MHz

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